Show Notes

• Google+: Fraser, Pamela
• End of the World — Not! Cruise
• Images of Io — NASA’s Photojournal
• Io, Galileo and Simon Marius — Gish Bar Times
• Controversy over the discovery of Haumea – Mike Brown’s Planets
• Io exploration overview — NASA
• Io in mythology — Wiki
• Voyager spacecraft and Io
• Galileo spacecraft and Io
• Magma Ocean Flows Under Io’s surface — Universe Today
• NASA’s Plutonium Production Predicament – Universe Today
• Juno Mission

Transcript: Io

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Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing?

Fraser: Good. And again, we’re recording well into the future. It’s early December, but we’re recording this for late December because you’re going to be cruising somewhere.

Pamela: Yeah, something like that.

Fraser: Not doing anything?

Pamela: I’m going to be off exploring the planet.

Fraser: You’re going to have a holiday? Sounds good…but once again, we’re recording this as a Google plus hang-out, and so if you want to participate, all you have to do is circle either me or Pamela and then we will give an announcement when we’re going to do the recording, and then you can just jump into the hang-out and we stick around for half an hour or an hour after the recording and answer questions, and it’s a really good time. So I highly recommend it — just circle one of us. And this is kind of cool because we’re recording at a really weird time, and so it’s an opportunity for our Australian listeners to join us on this one.

Pamela: And it just occurred to me we’re recording this a year before we’re going to be on a cruise together celebrating the world not ending.

Fraser: That’s right, or the end of the world — one or the other.

Pamela: Well, yeah…either way, we’ll be together.

Fraser: We’re pretty certain it’s not going to end. Yeah, and so you can go and find out about that at astrosphere.org/endoftheworld?

Pamela: Just go to astrosphere.org. It’s the lead story right now.

Fraser: And there’ll be a link to that. So once again, December 2012, we will…we’re going to be doing a cruise with a bunch of other people, David Brin, astronauts, astronomers… It’s going to be a really good time. So you can check that out on our astrosphere website. We sell it so well. We’ve got a whole year to nag you about this. Actually, you know, I think it’s going to fill up, and we haven’t really publicized it outside of just the AstronomyCast shows, so I’ll probably start talking about it more on Universe Today, so and then it will sell out. I highly recommend you go with us. OK, let’s get on with it.

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Fraser: So if you want to see one of the strangest places in the Solar System, look no forward than Io, Jupiter’s inner Galilean moon. The immense tidal forces from Jupiter keep the moon hotter than hot, with huge volcanoes blasting lava hundreds of kilometers into space. And, Pamela, before we get into this, I have to let you know my daughter proposed tonight’s topic.

Pamela: Yes, she is the one who text messaged me to find out if we could do this.

Fraser: That’s right. So she texted…“Can I text message Pamela?” I’m like, “Yeah, OK.” “I think you guys should do a show on Io.”

Pamela: And I was really confused because I thought she’d written “lol” and lost the second “l” because it was an iphone.

Fraser: No, no, no, she’s ligit. She knows her science; she loves Io.
OK, so then, you know, we got a whole episode to just talk about this moon and, you know, there are so many really interesting things about Io. Let’s get started — and I think, you know, we gotta get started with the discovery. When did we find out about Io?

Pamela: Well, finding out about it…there’s always this lag between discovery and publication. So here we have this interesting…the first dude was too slow, so according to anything you’re likely to read, it was Galileo who discovered Jupiter’s moons in January of 1610. The first night he looked, he probably saw Europa and Io pretty much stacked on top of each other and couldn’t separate them, but then on January 8, he clearly saw the two of them as two distinct objects, and he went on to publish this just a couple of months later in March of 1610. Now the thing is, Simon Morris, another person who’d already figured out how to use telescopes to look up, claims that he saw them in December of 1609. And that would have been one month earlier.

Fraser: Well, where are the photos?

Pamela: Well, yeah, that’s the thing. And he didn’t bother to publish his results, so here’s a clear case of: if you don’t share what you see with the world, you didn’t actually see it.

Fraser: And that has happened even recently with Mike Brown, [missing audio] killing Mike Brown from Cal Tech. You know, people discovering objects and then wanting to gather more science, and then other people figuring out what he’d done and trying to break the news before him, so that still happens. If you discover it, the race is on.

Pamela: Yeah. Publish, publish, publish!

Fraser: So then, I mean, do people have an opinion about whether he really did see it? I guess it really doesn’t matter, right?

Pamela: History gives all the credit to Galileo. And you know Galileo suffered enough for his good work — might as well allow him to keep all the Galilean moons for himself.

Fraser: And so what was he able to see?

Pamela: He saw a small star that appeared to move back and forth beside Jupiter — it was very unexciting. In fact, if you go out with a good pair of binoculars, or a Galileoscope (you can still buy Galileoscopes at Galileoscope.org)…with a Galileoscope, they actually have a lens that allows you to see exactly what Galileo saw, and it’s basically this little, itty-bitty, tiny field of view, where Jupiter is a smudge that you can just make out bands, sort of, on a really clear, perfect night, and then you see the Galilean moons dancing back and forth along a straight line like balls attached to a string.

Fraser: Right, and we’ve talked in other episodes — that was a mind-bending discovery because the previous thought was that everything orbited around the Earth, and here was something orbiting around Jupiter.

Pamela: And Kepler actually proposed that maybe these should be referred to as Jupiter’s moons, and Io being the closest in of the four Galilean moons, that was almost planet #1 orbiting Jupiter.

Fraser: So, then it was just stars and that’s all that anyone could see for years and years and years, right?

Pamela: Yeah, and the thing is all we had was this boring object; it had a great story behind it. While Simon Morris wasn’t credited with his discovery, he did get to name it, and it was named after one of Zeus’ mistresses. This is one of the neat things about the moons of Jupiter is for the most part, they’re people that Zeus seduced at one point or another in mythology. And Io, contrary to the look of the object, Io is named after a female that Zeus seduced and then when Hera, his wife, caught him, he quickly turned poor Io into a white heifer to try and hide what he had done, and there’s all sorts of myths about either the heifer ended up one of Hera, Jupiter’s (Zeus’) wife’s, basically, animals, and all sorts of crazy things, but basically you have this passive little white cow that we eventually found out was anything other than a passive white little moon.

Fraser: Right, right, but then even with better telescopes, over the centuries, we didn’t get much better of a view.

Pamela: No. In modern times, or at least within the past 150 years or so, we were able to make out as we looked at it that, well, it appeared to have slight changes in color across the two hemispheres, and by watching it over time, seeing how the colors varied over time, people were able to figure out that it’s not pear-shaped. Because that’s the thing — when the north and south hemispheres don’t give off the same amount of light, it could either be because, well, the one hemisphere is smaller than the other, like a pear, or it can be, as the case actually is with Io, that you simply have dark splotches, and by watching it as it rotated, they were able to figure out that this is a little, tiny, splotchy something going around and around Jupiter.
?

Fraser: But they didn’t know why.

Pamela: They didn’t know why. That actually took until the 1970s, and the first time we figured that out was when the two Pioneer spacecraft made their way out and in December of ’73 and ’74, respectively. They flew by and it just wasn’t quite what they expected. They found high radiation, they found all sorts of weird materials — it was a silicate world, rather than an icy body. All the other moons that we were looking at, at that point, they were just big old blocks of ice, or big old ice balls, literally, but here they had a silica planet, and…or a silica moon, as the case would be. But the thing was, the Pioneers didn’t actually catch any of the volcanoes going off. For that we’d still have to wait another five years.

Fraser: Right, but I know that the Pioneer spacecraft were fairly low-tech for spacecraft. They didn’t have great instruments; they, you know, they didn’t probably make that close of a fly-by, so we just got a glimpse of what was going on, but I know that it was future spacecraft that really pulled things together.

Pamela: Right, so the next missions where things started to get interesting is actually a pair of missions that I’m just able to remember. Back in 1979 in March, Voyager I flew past Jupiter, and my parents made me take naps so I could stay up to watch the data coming back from the mission. And what was amazing is when they started when Voyager started sending back images, the scientists saw this planet that was covered in these weird pits and discolorations and these mountains and clear volcanoes, and as they went through the data, they were able to catch this amazing, basically, volcanic plume rising up over the edge of this small otherwise unassuming moon when you’re watching it from as far away as Earth, and it turned out this is the most geologically interesting thing that we have in the entire Solar System.

Fraser: And were astronomers, like, at all expecting anything like this?

Pamela: No. No. We had no clue anything like this was out there. It was just one of those things. I mean, there was a prediction from the Pioneer stuff. When Pioneer got there, there was absolutely nothing. So let me step back. From Pioneer there’s absolutely nothing weird anticipated. We’d gotten hints that there was stuff going on from Pioneers, and there had been a theory paper published that predicted that maybe tidal heating could cause some sort of a volcanism, but the level at which this was seen, the amount of sulfur and sulfur-dioxide getting thrown up, the arcs of material going between Jupiter and Io, none of this was predicted ahead of time. And it was like someone had taken every Dark Ages painting idea of Hades and turned it into a moon orbiting Jupiter. All that sulfur, all of that suddenly became real.

Fraser: I mean, I always imagined seeing, like, video of the volcanoes on Hawaii, or some of the…where you’ve got like these fountains of lava blasting in the air, and you’ve got you know, globs of lava, you know, plopping out of the volcano and landing as, you know, chunks of rock around. I mean, you’ve got this world, but it’s that times, I don’t know, like 1000, like you’ve got these streams of lava blasting out of the moon and, you know, creating these fountains of material. So let’s imagine, you know, that we were, like, standing above Io. What would we see?

Pamela: Well, so standing — that doesn’t even give you enough perspective. So, the thing to think about is the biggest volcanic eruption that most of us are familiar with from the news is the unpronounceable volcano that went off in Iceland in 2010, and that volcano threw material several miles up into the air, but it was still “single digit number” of miles into the air. Well, Io is about a third the radius of the planet Earth, not quite, it’s a little bit less than that, and it’s able to throw material into space roughly 1/3 of its diameter, so…[laughing]

Fraser: Hundreds of kilometers…

Pamela: It’s going hundreds of kilometers into space, and we just don’t have the…

Fraser: Well, it’s even more than that, right? I mean, as you said, it’s trailing away from Io itself and being absorbed into Jupiter.

Pamela: Right.

Fraser: It would be like volcanoes on Earth being blasted off and being, you know, making their way to the Sun.

Pamela: Or imagine having a volcano going off and the material in the volcano becomes part of the Northern Lights because that’s a closer analogy to what’s happening, or even better would be imagine if the Earth’s moon suddenly had a volcano that joined the Northern Lights because that’s essentially what’s happening is when these volcanoes go off — some of the material that gets released into the atmosphere, it gets…or not so much into the atmosphere, that gets released into space, it gets caught up in the magnetic field lines and forms these amazing streams of radioactive material that are kind of dangerous to the spacecraft that go through them. But this is plasma streams writ large, where volcanoes, gravity and electro-mechanics are all interacting in violent and amazing ways I don’t ever wish to calculate.

Fraser: No, or visit.

Pamela: Or visit. Yes.

Fraser: Right. And so, you know, we talked about, like, if you could stand on the surface, what would you see?

Pamela: If you could stand on the surface, you’d simply see a volcanic eruption that streams all the way into space. So if you’ve seen a rocket launch, you know how you can see the stream of material going all the way up into the sky and stretching out over the horizon? Well, this is a volcanic eruption that does the same sort of thing.

Fraser: And you would be standing on recent lava flows — no matter where you were.

Pamela: Pretty much. This is a constantly resurfaced world. There are some craters on it, but very few. So the surface is… we’ve seen areas basically the size of Arizona get resurfaced just in the years that we’ve been watching this planet with spacecraft.

Fraser: Wow!

Pamela: I keep calling it a planet – it acts like a planet! It’s not; it’s a moon. So, this moon…

Fraser: Now, when we see the pictures…we’ve seen the pictures from Voyager (and we’ve seen the updated pictures taken by New Horizons and Cassini), it’s got this strange, like, it looks like a bruised orange, like, it’s got these yellows, and oranges, and browns, and all these crazy colors, so what’s going on there?

Pamela: Well, the yellow is sulfur, so this really is every imagining of Hades turned into a moon. So, you do see when you look at the images some ices, you do see variations of the sulfur, where you get irons and you get different silicas mixed in, but that overwhelming yellow covering the whole moon — that’s just sulfur and sulfur-dioxide.

Fraser: Is it like snow, or…?

Pamela: No, think of it as they talked about with the unpronounceable volcano that went off in Iceland. All of the silica ash that would destroy airplanes if airplanes flew through the ash — well, that yellow-y stuff that you’re seeing is similar sorts of material. It’s all the silica stuff that got thrown into space, all the sulfur ash that got (I don’t know if ash is the right word), all of the sulfurs that got thrown into space, and then, gravitationally, some of it gets pulled back down — a lot of it gets pulled back down, and it’s kind of amazing the size of the arches that some of these plumes make as they go up, and then fall down far away from their volcanoes.

Fraser: And, uh, someone from the hang-out wanted to know: why is there so much sulfur?

Pamela: You know, this is actually one of those things that when I was researching for this show I was trying to find. I couldn’t find a quick answer anywhere. This is a world that has a disproportionately large amount of silicon, a disproportionately large amount of sulfur, and its composition is just different from everything else, so somehow when the Solar System was differentiating, this one rock ended up in a part of the Solar System that for the most part is ice and gas.

Fraser: And, so then what…and then what is causing this? I mean, now those regular listeners to the show will know, but I think it’s quite an amazing story. So what is causing this moon, unlike all the rest, to be so volcanically active?

Pamela: Well, it has an unfortunate location. So, as I was saying earlier, it’s one of the four Galilean moons, which means it is orbiting Jupiter and it’s the inner most of those four, and the others are Europa, Ganymede and Callisto, and the inner three: Io, Europa and Ganymede have orbits that have, over time, settled into what’s called a resonance. So for every two times Io goes around Jupiter, Europa goes around once, so if Io’s at the top of Jupiter and Europa’s at the top of Jupiter and you’re looking down from the north (so that’s kind of a weird way to think of it), you’re looking…you’re hovering above the north pole, looking at the planet, and at the top of the planet, you see Io and then directly above it you see Europa, then the next time Io gets to the top, Europa’s going to be exactly at the bottom. Now, Ganymede is doing this exact same thing, but for every four times, so every time that Io and Europa are lined up, Ganymede’s going to be lined up with them, and this resonance: this 2:1, 4:1, 1:1 resonance between these three moons forces Io to sometimes be closer to Jupiter, sometimes be further from Jupiter, and to undergo constantly changing gravitational pulls, and this constantly changing gravitational pull has the effect of, over and over and over, squishing Io like a stress ball held in the hand of an angry Roman god, which according to mythology it is [laughing], so…or in this case, yeah, I’m not going to go into the mythological connotations on this one.

Fraser: But it’s that squishing, and then un-squishing, and then squishing, and then un-squishing — just heats it up, and there’s, I mean there are so many examples that you can think of something very similar. You can take a rubber ball and squish it and un-squish it.

Pamela: If you have a small child that you want to tire out, hand them a small rubber ball and have them bounce it over and over and over with a paddle, and eventually, it will actually change temperature from doing this.

Fraser: Yeah, I mean, bounce it up and down for a while, and then touch it, hold it, and you’ll feel the warmth coming off of the ball and that’s because it’s the same process.

Pamela: In this case, this constant squishy-squishy-squishy that it undergoes is able to build it up to a temperature of 1200 degrees, and it’s estimated that anywhere from 20% or more of its mantle is melted and that there’s a vast subsurface — basically, oceans of lava. The surface is probably about 7 miles (12 km) thick, or more. It’s at least that thick, but it’s certainly not more than 25 miles (40 km) thick, so this is a world with a very, very thin surface over a rather hot interior of magma, and all of that’s just under pressure waiting to break through and fly hundreds of kilometers into the atmosphere.

Fraser: Right, and so it’s that tidal forces that…well, I guess it’s a mixture, right? The tidal forces are creating huge pockets of this liquid that’s increasing the pressure, and then at some point it has to find a way out, and you get these cracks in the surface, and you get these geysers, and then at the same time it’s a smaller object than Earth and so it’s got less gravity, and so things can just fly further when they blast out.

Pamela: Right, and what’s kind of awesome is not only are there the volcanoes, but there’s also regularly-formed mountains from all of the forces that the crust is undergoing from having all of this squishing, all of these tidal forces, all of the pressure from the magma, and some of the mountains that are forming are actually bigger than Earth’s Mt. Everest. So here again you have something a little less than a third the diameter of Earth, mountains bigger than Earth, volcanoes spewing material up to what on Earth would be the orbital height of the Space Shuttle — I mean, just imagine if one of the volcanoes in Iceland or Indonesia or Hawaii went off and hit the Space Station! That’s the scale that we’re looking at here!

Fraser: And again, like, I think about how you’ve got Europa, which is a little further out, which possibly has, you know, a crust of ice with liquid water underneath, and it’s that tidal flexing has made the water liquid. But with poor Io, it’s the tidal flexing has made the rock liquid. It’s just a different sense of scale. Now, you know, we always think: Europa, Callisto — maybe there could be some life? Enceladus? What do you think are the chances of finding life on Io?

Pamela: You know, I think if we’re going to find something with something more than a few cells inside, Europa’s the place to look. But Io…we find out at Yellowstone, here in America, all of these amazing thermophiles that live in the hot springs, that live in the extremely sulfuric acid-rich pools, that live in these bizarre chemistries, and these bizarre chemistries are at a completely different pressure and gravity than Io, but compositionally, they’re just as toxic, and if stuff can live in those toxic environments on Earth, there’s no reason to think that stuff couldn’t evolve to exist in the similarly toxic environments on Io. You have a thermal gradient, you have presumably some sort of liquid (that part we don’t know for sure), but you’ve got that thermal gradient and that is one of the things that drives the chemistry of life.

Fraser: Yeah. I mean, if you’ve got a source of energy, that goes a long way… You [missing audio] in helping out life, so it’s really interesting. Now are there any plans to re-visit Io?

Pamela: Well, we want to, and this is one of the problems we’re dealing with now.

Fraser: Yeah, you and I want to. We want Io visited, but…

Pamela: [laughing]

Fraser: Are there any plans by you know scientists? Perhaps space agencies?

Pamela: One of the problems we’re dealing with right now is lack of funding, and this gets reflected in two fairly significant ways. One of them is we just don’t have any more of the radioisotope-driven engines that you need to go out and explore these distant locations in the Solar System; we just don’t have the radioactive materials we need to build more of them. And Congress cut the budget to turn on the facilities necessary to manufacture those radioactive isotopes. And then there were plans to explore the moons of Jupiter in greater detail, but that spacecraft doesn’t necessarily look like it’s going to happen anymore. As they cut more and more of the U. S. budget, as we move toward having our own form of austerity measures, we’re losing our scientific dreams, and so I have to say probably not in the next 10 years is anything going to launch to explore these moons. Now, we do have a spacecraft on the way out to Jupiter; this is Juno. Yeah, so Juno’s going to do a great job at what it does. It’s going to be mapping the magnetic fields of Jupiter, and it’s that magnetic field that carries around the radioactive materials. It’s going to be doing a great job measuring the composition of Jupiter’s atmosphere, and mapping out the gravity of Jupiter. It’s going to do some really awesome things, but this isn’t an imaging mission. It does have a camera on-board; it’s a camera designed to take pretty pictures because we want pretty pictures, but it’s not really a science camera. So the science is going to be the type of stuff that makes the scientists happy, but doesn’t necessarily end up on the nightly news. And so Jupiter is going to reveal a few more secrets, but not necessarily a few more pretty pictures.

Fraser: Oh, wow. OK, on that sad note…well, thank you very much, Pamela, and we’ll talk to you after Christmas.

Pamela: That sounds great, Fraser. I’ll talk to you later.

Fraser: Alright. I hope everybody has a great Holiday, and we’ll talk to you again next week.

Pamela: Sounds great. Happy Holidays, everyone.

Show Notes

• Google+: Fraser, Pamela
• NASA’s NEO Program info on the Torino Impact Hazard Scale
• Current Impact Risks (as of this recording)
• Asteroid 2005 YU55 — Universe Today
• Richard Binzel: Three Questions on Near Earth Asteroids — MIT
• News story from 1999 detailing the Torino Scale — Terradaily
• 1/2mv^2 — Kinetic Energy
• The Torino Scale — Universe Today
• Torino Impact Scale Explained — NASA
• What Damage Have Meteorite Impacts Done in Human History? – Oberlin College
• Chíing-yang Meteorite Shower of 1490
• Campo del Cielo Meteorites
• Tunguska Impact -- Science@NASA
• Barringer Crater (Meteor Crater)
• Predicting Apophis’ Encounters in 2029 and 2036 -- NASA
• AstroGear

Transcript: The Torino Scale

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Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Good! So once again, we’re recording AstronomyCast live as a Google plus hang-out, but we’ve muted them all so you can’t hear any voices. Everyone’s going to wave in silence. So if you want to join us for future recordings of AstronomyCast, all you have to do is join Google plus and then circle me or Pamela, and then when the hang-out is kind of approaching, we will…

Pamela: …warn you!

Fraser: …mention it, warn you, and then we’ll start the hang-out up, and it’s kind of a race to get in, but it’s super-fun, and then we try to leave the hang-out open for another half hour, forty-five minutes after we do the recording, and we answer questions and yak about space and astronomy and photography, dogs…

Pamela: Stuff.

Fraser: Yeah, so it’s awesome and super-fun, and we’d love to have you guys join us. So when you hear of a looming asteroid strike, do you wonder what to do? Should you go into your underground bunker, evacuate the state, or leave the planet? Fortunately, astronomers have developed the Torino Scale, a handy measurement that incorporates both the likelihood of a strike, and the amount of devastation. This is good; this was needed for a long time, you know? The Torino Scale?

Pamela: Well, I’m not sure it’s needed so much as it’s just one of those things of die/not gonna die, and probabilities.

Fraser: I mean, that was my intro, right? Asteroid YU 2005 is going to strike the Earth, you know? I gotta know! Should I evacuate Europe? Should I leave the planet? Or is it sort of no big deal, I’m just going to get out my binoculars and watch it strike the neighboring city, so um, you know? So, I think, now we’ve really got a really precise way to be prepared. So where did this concept come from?

Pamela: Well, back in the 1950s, as we started to realize more and more and more that our planet is kind of covered in asteroid impacts, people started thinking, well, so what do all of these different types of impacts mean?” And, well, any time you get scientists thinking hard about something, they’re going to end up coming up with a numerical way of quantifying all of it.

Fraser: Right, like the Richter Scale…

Pamela: Right.

Fraser: Oh man, what is it? The Fuji…F-Scale for tornadoes? The scale for hurricanes…

Pamela: Right, so we have all these different scales, and it was finally professor Richard P. Binzel, who (he was working at MIT at the time)…it was only in 1995 that he presented this at a conference, and so this is a fairly new way of looking at the Universe and saying this is numerically quantified how it’s going to destroy us, and he gave his presentation, actually at a UN-hosted conference, where they were discussing future destruction of the planet Earth.

Fraser: Right, right I, again, you can just imagine scientists going, “Is there some way we can put a number to this?” You know? So right, OK, so he presented, he sat down and decided he was going to be the one to come up with a name, but it doesn’t have his name.

Pamela: No, that’s actually one of the things about it that, to me, was kind of confusing until I realized it ended up getting revised in June 1999 in the Italian city of Turin, which if we weren’t Americans, we would call the city of Torino. So it’s named after the city where the current version of it, more or less – it got revised again later to make it more press-friendly, but it got named after the city where the current, all-but-final version of it was invented.

Fraser: Right and that sounds like a nice, sort of, way to sort of cap it off, and then we’ve got this nice measurement scale from this point on, and it’s actually taken off pretty well, I mean, I can…that’s in my time. When I started Universe Today back in ’99, I can kind of remember when they started to incorporate that scale, and we’ve been watching it ever since. And now, every asteroid that has any kind of likelihood of hitting the Earth gets, you know, will get a measurement on the Torino Scale.

Pamela: And what’s interesting is you might be one of the reasons why in 2005 they felt the need to re-change some of the wording. So this is a scale that goes…

Fraser: Me? What?! What?!

Pamela: Well, it’s a scale that goes from 0 to 10, and it used to be that objects that were Torino level one, which the official definition is “a routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger.” It goes on a little bit longer than that…

Fraser: We’re going to go through the scale in a second, but yeah.

Pamela: So, this is now called “normal,” so anything Torino level one is “normal.” Well, it used to be that it was “events meriting careful monitoring,” and so many members of the press went a little nuts — not saying you’d go nuts, but you’d probably mention it anytime something got a Torino level of one, that they’re like, “OK we’ve got to rename this so people don’t panic.” So in 2001, it went from “merits careful monitoring” to “normal.”

Fraser: Well, and the thing is if you go through enough of these, you see the way it always plays out, which is that somebody discovers an asteroid, they quickly assign a Torino Scale to it, and then, you know, and then everybody points their telescopes at it and gets careful data on it, and then, always, every time so far, the Torino…it just drops back off the Torino Scale because they now know that it’s not going to be any kind of risk, but there’s this gap where the press goes bonkers, and people freak out.

Pamela: Well, it’s fun!

Fraser: It’s fun?

Pamela: Well, I…think about it. We live in a world where people celebrate death and destruction, and pepper spraying, and all these other crazy things that make it into the news. If it bleeds, it leads, and destroying of the planet counts as bleeding.

Fraser: Right, it is big news. Although people gotten a lot more used to it, I’m still waiting for people to get numb to asteroid discoveries and asteroid risks, and they still don’t. I mean every one of them – we had a huge boost when, what was it? 2005? huge boost of traffic to the Universe Today because everyone was searching for it. OK, so then what is the purpose, like, what does the Torino Scale measure?

Pamela: It’s sort of the planetary risk level for asteroids the way we have a color system to describe nuclear threats, the way we have a color scale to describe airport safety threats, it’s just another one of these three-minutes-before-midnight threat assessments, so if it’s zero, we’re good. It’s going past the Earth, we’re fine, just smile and watch — and ten is we all die.

Fraser: We all die. Right, but the point is when you think about the Fujita Scale (thank you to the people in the hang-out who reminded me of the name), but when you think of the Fujita Tornado Damage Scale, you have like speed of winds, and the size of the tornado itself. When you’re thinking about the scale for the hurricanes, you’ve got, sort of, the speed of the winds, and that’s just it, right? When you’ve got the Richter scale, we’ve got the amount of shaking, so what are we measuring with the Torino Scale?

Pamela: ½MV squared.

Fraser: Right, ½MV…right! So we’re measuring the momentum of it?

Pamela: Well, no, no, no — momentum is mass times velocity. This is energy.

Fraser: Right, total energy.

Pamela: So, we have to worry about what’s its mass, what’s its velocity as it’s coming towards us, and it also has to deal with, in addition to these measurable things, it also has to deal with how likely is it that those measurable things are going to impact their energy, well, on our heads.

Fraser: So Jupiter is going to have a lot of mass and velocity, but it isn’t going to hit us.

Pamela: And at the end of its day, its velocity really isn’t that bad, so… It just has a giant mass that isn’t going to hit us.

Fraser: Right, right. It isn’t going to hit us, and the trick is if they hit us. So, it’s both the velocity and the mass of the object, but also that probability of whether it’s going to hit.

Pamela: So, we have things that have high probability, low mass, low velocity, do zero damage; things with high mass, high velocity that are somewhere else in the Solar System and aren’t going to hit us and thus do no damage, but it’s the things in between with a moderate probability of hitting us, and enough mass and velocity to make it through our atmosphere — those are the interesting things that we like to look at.

Fraser: Right, and I know that the danger on the Torino Scale — it could be a high probability, but not a lot of damage, and it could be the other way – a lot of damage, but a low probability of hitting us, and the Torino Scale nicely accounts for both of those.

Pamela: Right, and the thing that anyone that’s gone out and has looked up for any period of time has realized is we’re constantly getting hit with stuff, but the catch is we’re constantly getting hit with stuff that’s of a size that doesn’t matter, so about every 30 seconds a 1 millimeter object hits our atmosphere – shooting star – little, tiny, probably-not-noticed shooting star. About once a year, an object one meter in diameter hits us, burns up, does no damage, and we notice over and over and over in the satellites that are looking for things being blown up — nuclear assessment and things like that — there are dozens to hundreds, depending on how much energy you’re looking at, massive explosions in our atmosphere, Hiroshima-sized explosions in our atmosphere from things that hit us on a regular basis that no one notices because it’s out over the ocean, or over the prairie or something.

Fraser: So, let’s go through the Torino Scale. Let’s start with the bottom, I guess, zero and walk our way up to ten.

Pamela: OK.

Fraser: So what is zero on the Torino Scale?

Pamela: Uh, nice lightshow, maybe — probably not. This is the YU 55, so things that go past that we know exist, they’re not coming anywhere near us, but we can look at them as they go by.

Fraser: So we are certain that they will not do anything to the planet.

Pamela: We are absolutely, positively certain they will do nothing to the planet.

Fraser: OK, so what is a “one” on the Torino Scale?

Pamela: A one is “the chance of collision is extremely unlikely,” about the same as a random object of the same size striking the Earth within the next few decades.

Fraser: In other words, objects are randomly hitting our…what? hitting our atmosphere every few decades anyway, and so there’s just neither much risk, nor much damage if it does.

Pamela: It actually kind of boils down to, “we don’t know much about this object yet. It’s as likely to hit us as anything else, and anything else is probably not going to hit us.”

Fraser: Right. OK. Let’s move on, I want to hear the next one.

Pamela: OK, so this is number two: “events meriting concern,” yellow zone number two. Number two just says “a somewhat close, unusual encounter, collision is very unlikely.”

Fraser: OK. Three?

Pamela: “A close encounter with a 1% or greater chance of collision capable of causing localized destruction.” This is your neighbor’s house is destroyed.

Fraser: Well, it’s more than that, right? It’s like a city.

Pamela: Yeah, but it’s still confined to a region. So we’ve experienced these things in human memory, so it’s…

Fraser: Would that be like Tunguska?

Pamela: Well, Tunguska, yes. It would also be back in 1490, there was a Chinese village that reportedly had about 10,000 people killed.

Fraser: Right, OK. Yeah, and I know we have lots of these iron meteorites that are found in, like, what is it? Campo del Cielo meteorite? And there’s…so like Tunguska. for example. was like a…what? 1908 asteroid, comet, UFO traveling through a wormhole, um…

Pamela: [laughing] Something blew up in the atmosphere and flattened part of Siberia.

Fraser: Right, so in other words, it didn’t cause any damage to Paris or Moscow, but it sure ruined a chunk of the Siberian forest.

Pamela: Right.

Fraser: OK. Alright, so, that is localized damage. Let’s keep going.

Pamela: OK, so now we move out of yellow into threat level orange, and these are threatening events. And I just sound far too mirthful reading these, but destruction is fun! So number five is “a close encounter with a significant threat of a collision capable of causing regional devastation.”

Fraser: Regional…so when they say regional, are they talking about, like, Europe? Great Britain?

Pamela: Yeah, pretty much.

Fraser: Yeah, OK.

Pamela: Let’s just, like, get rid of Australia.

Fraser: So, in other words, if that happens, and great, it hits Australia, then you and me over here in North America would probably be alright.

Pamela: Right, so here we’re not talking enough material getting thrown into the atmosphere that it causes global cooling. We’re not…we have to worry about things like massive fires being caused, but as long as that doesn’t happen, we’re probably good. As long as it’s elsewhere…

Fraser: And that’s only half way up the scale.

Pamela: It’s only half way up the scale, but these are still probable things, so there’s a significant threat, but not a certain threat.

Fraser: Right. OK, keep going up.

Pamela: So threat level six is “a close encounter with a significant threat of a collision capable of causing global catastrophe,” so this is the dinosaurs dying — perhaps.

Fraser: Right, but I think the key there, and this is really weird, right? Because this is essentially complete destruction of the Earth, of all life on Earth, but we’re still…but maybe, right? That’s the trick.

Pamela: It’s the maybe that’s important. It’s the maybe that keeps it from being a red.

Fraser: So maybe the whole Earth will be destroyed, but maybe not. Who can say? Right. OK. Let’s keep going.

Pamela: OK, so threat level seven is “a close encounter with an extremely significant object capable of a collision causing a global catastrophe.”

Fraser: That’s seven?

Pamela: That’s seven.

Fraser: Well, hold on a second, so that is again global catastrophe, and a very high likelihood of a collision?

Pamela: So we went from “significant threat” at six to “extremely significant threat” at seven.

Fraser: Are we going to be destroying the Universe by the end of this scale?

Pamela: We’re just increasing certainty as we go.

Fraser: OK. Alright, it’s just hard to say with these words, you just want, like, is it a 75% chance? Is it a 33% chance?

Pamela: Yeah, they don’t do that for us.

Fraser: OK, let’s go on to level eight. I’m scared now.

Pamela: OK, so we’re now going into threat level red. These are certain collisions.

Fraser: Aaah…certain. 100% chance, yeah… There’s a 100% chance that an asteroid is going to strike. OK.

Pamela: So at threat level eight, we have “a collision capable of causing localized destruction. Such events occur somewhere on Earth between once per 50 years, and once per 1000 years.”

Fraser: So, this would be astronomers detecting a Tunguska-level event, or maybe meteor crater in Arizona, right? And saying…Barringer Crater? Yeah.

Pamela: Beringer.

Fraser: Yeah, Barringer, and saying, “We are absolutely going to get hit by a Barringer. It’s probably going to hit, you know, Paris. Everybody ought to move away from Paris.”

Pamela: See, I’m not actually sure if Barringer is localized or regional because of all of the stuff it tossed into the atmosphere.

Fraser: Right, right, you know maybe that’s just… Yeah, but what is it? A Tunguska happens every 100-1000 years, so it sounds like that’s sort of in the scale.

Pamela: It’s definitely Tunguska.

Fraser: Well, I mean Tunguska flattened a forest for 1000s of kilometers, right? …square kilometers, so it was a pretty big event.

Pamela: Yeah, it was kind of awesome.

Fraser: …dig out a big crater, but that’s kind of what we’re talking about. I can see maybe Barringer being even worse, but the point being…but it’s interesting, you know, the previous level was, you know, “the Earth is completely toast probably,” and now we’re back to “a very small part of the Earth is toast for certain.” OK.

Pamela: Yes. OK, so threat level nine is “a collision capable of causing regional devastation. Such events occur between once per 1000 years and once per 100,000 years.”

Fraser: Ouch. OK.

Pamela: So this is, “We see it coming. Everyone get on a plane and go somewhere else now, please. That part of the planet is about to end.”

Fraser: OK, and number ten…

Pamela: Number ten: “a collision capable of causing a global climatic catastrophe. Such events occur once per 100,000 years or less.”

Fraser: 100,000 years or less?!

Pamela: Yes.

Fraser: So we’re not even talking about like a KT, you know the one that ruined the dinosaurs 65 million years ago; we’re talking about something much less damaging.

Pamela: Well, so this is where you end up with people arguing over what counts as global catastrophe. So, does it count if it changes the weather patterns? Does it count if you have mass extinctions? because we certainly haven’t had a mass extinction in a while. So, people do squabble over those kinds of things.

Fraser: But we are talking about the end of civilization as we know it.

Pamela: Yes.

Fraser: No matter where you live, civilization is going to come to an end.

Pamela: Yes.

Fraser: Wow! So since the Torino Scale has been developed, how bad has it gotten?

Pamela: Well, we made it up to four once, briefly, but the nice thing about the scale is it’s self-correcting as you get more data because up until you get into that red zone, all you’re really talking about is things that might hit the Earth, and how bad it’ll be if they happen to get to “might,” or happen to get past “might.” So Apophis, which we’ve all heard about in the news, is the big one that everyone freaks out about, and we now know it is a zero. There is no chance that we know of that on its next pass past the Earth — and this is all we’re worrying about is the scale’s looking ten years out into the future. It’s not going to hit us then.

Fraser: Although, there’s a possibility of that in 2029, and a completely unknown possibility in 2036.

Pamela: Yeah, so it currently still has, for the 2036 encounter, a rating of a level one because we need to wait and see what happens in 2029 because its orbit will get changed as it goes past the Earth.

Fraser: So the highest…so Apophis, you know, rose in the charts to four.

Pamela: Yes.

Fraser: Which I think they kind of regretted doing that, but…

Pamela: Yeah, well, it was an honest…you see, the problem is that science is something where we’re constantly learning new things, and… It was an honest level four..

Fraser: Yeah. There was enough uncertainty…

Pamela: There was an object in 2006 that temporarily got a level of two, but it got downgraded quickly, so in general, things don’t make it very high on this scale.

Fraser: And they don’t last long on the scale.

Pamela: Right, and what’s kind of amazing is we have all sorts of surveys that are essentially accelerating the rate at which we discover asteroids, so even as we’re discovering more and more and more and more asteroids on a regular basis, we’re not discovering more Earth-destroyers as we go.

Fraser: Right, and in fact, I think, you know, we mentioned this in another show, we’re finding all of big nasties, and have really ruled out a lot of impacts in the foreseeable future.

Pamela: Right.

Fraser: The size of asteroids is the problem that we’re looking for now, and they’re getting smaller and smaller, which is kind of a relief.

Pamela: And the thing interested me, in researching the show, I went through and I looked up historical accounts of people getting clobbered because you’ve probably seen on TV if you’ve ever watched any of the bad science channel specials, the story of the car that got hit, the story of the lady that had one come through her roof, and bounce off her radio and hit her…

Fraser: The dog that got killed…

Pamela: …the dog that got killed, so there’s all these stories that are always in the news. But the thing that got me that I didn’t know about is there’s a number of different (number being 3), number of different areas getting walloped by basically a rain of solar system gravel, and so there’s this story in 1490 that people argue over how accurate the numbers are, but according to the histories, the Chinese province, that I’m about to mispronounce, Chíing-yang, was hit by a whole bunch of asteroid fragments that killed about 10,000 people, and that’s kind of dramatic. And there was a village in Africa that had a rain of fragments, and there’s just all these stories of places basically getting rained on with shards that damage roofs — it’s like a massive hail storm, usually, but that seems to be the more frequent way of individuals having close encounters with asteroids.

Fraser: And so just as we’re recording the show right now, how many objects are on the scale?

Pamela: Well, everything’s on the scale…

Fraser: Oh, sorry.

Pamela: …because everything gets a Torino level.

Fraser: Sure. How many are above one?

Pamela: Well, we have nothing above one.

Fraser: Wow.

Pamela: So there are two objects that we don’t know their orbits well enough to give them a zero, so there’s two things that we’re still following up on that have a rating of one in the near future. So, we’re doing pretty good. With everything we’ve discovered, we are safe for at least ten years, and for the things that we know, with the exception of Apophis, there’s nothing to worry about.

Fraser: Alright. Wait a minute – that was like a nice, pleasant, happy ending to that.

Pamela: That’s why it allows me to giggle while reading the scale.

That

Fraser: That was good. I like you reading the scale. People should…we should have a separate recording of that and then we could just listen to that show – you doing the Torino Scale. Right? Well, that was great. Well, thanks a lot, Pamela.

Pamela: It was my pleasure.

Fraser: And next week, I think, we’re going to actually specifically talk about Tunguska.

Pamela: Yes.

Fraser: And that will be kind of cool. And that was from a listener who suggested that idea for a topic, so we will…we live only to serve, and we will do that episode next, so….

Pamela: And one side comment before we take off: we are recording this as we enter the Holiday season in 2011, and we just posted a bunch of new stuff in our store, including a new t-shirt design for the Venus transit next year.

Fraser: Cool!

Pamela: So if you’re gearing up in your preparations for the Venus transit, and you want a map on a shirt of where the transit is visible, we have that shirt for you. So, go to Astrogear.org and get stuff for the Holidays for the people in your life, and for yourself while you’re there.

Fraser: Sounds good. Alright, well, thanks a lot, Pamela.

Pamela: Sounds great!

Show Notes

• Solar Maximum prediction for 2013 — Science@NASA
• The Solar Cycle — Marshall Space Flight Center
• Animation of the Sun’s magnetic field lines over time -  Windows to the Universe
• Earth’s Inconstant Magnetic Field -  NASA
• Sunspots come in pairs — Universe Today
• Stunning aurorae in Oct. 2011 seen at low latitudes (and bright red in some regions.) — Universe Today
• Image/video of magnetic field lines on the Sun – Universe Today
• Video from the Solar Dynamics Observatory of magnetic field lines snapping and material being flung out from the Sun — Lights in the Dark
• Long periods of no sunspots – Science@NASA
• Where are the Sunspots? (article from 2008) — Universe Today
• Maunder Minimum — Universe Today
• Using Ice Cores to Study Solar Influence on Climate — Australian Dept. of Sustainability
• Solar activity and climate: is the Sun causing global warming? – Skeptical Science
• El Nino Found to Drive Tropical Civil Wars – Scientific American
• Solar Flare — NASA
• CME –NASA
• Magnetohydrodynamics — Wiki
• STEREO Mission
• Solar Dynamics Observatory
• Astronomers Track Flares on a Distant Star — Universe Today
• Studying Starspots – Ohio Wesleyan University
• AC Episode #163: Auroras
• SpaceWeather.com
• Aurora Season (aurorae on the equinox) — Science@NASA

Transcript: Solar Activity

Download the transcript

Fraser: Welcome to AstronomyCast our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Good…and we’re once again recording this as a live Google plus hang-out. Hello to all of our Google plus friends. They’re all waving; you can’t see it…joke never gets old. Alright, so we don’t have a lot of time for chitchat; you have an airplane to catch so we’re just going to roll. The Sun looks like a harmless ball of fire in the sky: warm, life giving and forever unchanging, but we know better, don’t we? It’s really a massive ball of churning hydrogen plasma encased in twisting magnetic field lines, speckled with sunspots and constantly disgorging vast balloons of radiation and charged particles. The Sun is very active indeed. And you know what’s cool, Pamela? We are nearing the solar maximum.

Pamela: Well, we hope we are nearing the solar maximum.

Fraser: Yeah, It’s very weird this year, very weird…strange times we live in.

Pamela: Yeah, yeah, so we’re recording this in November of 2011, and they keep changing when they think our current solar cycle is going to peak just cause it’s such a weird one. It’s behaving oddly, and so the Gaussian fits aren’t working so well. We’re currently looking at a maximum probably around May of 2013, which for an 11-year cycle is right around the corner.

Fraser: Right. Alright, so I was getting ahead of myself, so let’s go back, go back. So, the Sun is a ball of plasma hydrogen pulled together by its gravity in a nice state of equilibrium with the light pressure pushing out and the gravity pulling inward, and that would seem to be the sort of state of perfect balance, but the Sun is very active, so what’s going on?

Pamela: Well, on the grand scheme of stars, the Sun is actually very boring and very inactive, but what we’re realizing…

Fraser: Well, the show’s over then. Thank you very much.

Pamela: [laughing] What we’re realizing is when you look at any star, even our boring Sun, in enough detail you start to see all kinds of crazy variations, and our sun’s most notable variation is its sunspot cycle, so if you watch the Sun for 11 years, you’ll see it goes from having no or virtually no sunspots to having those really pocks-mark covered face that’s just covered in sunspots, and what’s interesting is as you watch over time, where the sunspots appear also varies. And this entire cycle repeats every 11 years, and if you have the right tools to watch, you’ll actually realize that what’s happening is for one set of 11 years, you have a north magnetic pole on the top of the Sun and the south magnetic pole on the bottom of the Sun, and then for the next 11 years, that will switch, and so what we’re watching is, over time, the Sun’s magnetic field is tying itself literally in a knot and flipping itself over, and in the process we end up with magnetic field lines poking through the Sun, and those magnetic field lines poking through actually change how much light that we’re getting here on the planet Earth.

Fraser: So just to sort of think of this as an analogy here on Earth, it would be as if your compass pointed north, and then 11 years later it flipped around and started pointing south.

Pamela: That’s exactly what we’re seeing with the Sun, and what’s cool is along the way we see this change in, well, the amount of light that we get that tracks beautifully with the sunspots, so the more sunspots we get, the more energy we get. It’s a very small effect, just a little over a watt per square meter across the planet, but that little variation that we see, that’s enough that, well, it actually slightly changes the temperature on the planet.

Fraser: Well, I guess the part that I find kind of confusing is why does the Sun even have this activity, this cycle? I mean, as I mentioned earlier on, I mean, it’s compressed down, it’s got this balanced state — shouldn’t it have figured out these fluctuations over the course of 4 and a half billion years?

Pamela: So the problem with astronomy is there’s basically two things that we’re trying to get a handle on: one of them is dust, which luckily isn’t a huge problem when looking at the Sun, and the other one is magnetic fields, and that one is a huge problem when looking at the Sun. So, we know that (we think we know, at least) that the Sun’s magnetic field is generated somewhere at the interface between where energy is getting transported via convection, via big blobs of hot material rising, giving off their energy at the surface of the Sun, and then sinking back down, and via radiative transfer, which is where you just have the light radiating through the material and transporting energy along the way, and exactly what causes this magnetic field to arise at this particular point in the Sun, we don’t fully understand. What causes it to turn itself inside out and flip over on a not-precisely-but-pretty-close-to 11-year cycle, is also something that we haven’t quite figured out. I mean, we know in big brush strokes that it has to do with differential rotation of the Sun. This is where you have giant ball of, well, plasma gas; that’s not a solid. Here on the Earth, the equator, it rotates in lockstep with Massachusetts, in lockstep with Siberia, in lockstep with South Africa…

Fraser: Right, cause it’s a solid.

Pamela: No matter where you are, because it’s a solid, everything rotates together. Sun’s not like that. With the Sun you end up with different parts of the planet rotating at different velocities and as a result, well, different parts get carried ahead while others lag behind, and this seems to be partially if not fully responsible for the magnetic field becoming a tangled mess over time, and as the magnetic field tangles itself up, it ends up turning itself inside out, and we don’t fully understand the details — we just know it happens. I love observational astronomy; theorists have a challenge.

Fraser: Yeah, and I’ve seen some really interesting animations, maybe it was on a Nova episode… We’ll try to link to something in the show notes where you can see these animations of, or simulations of what the magnetic field lines look like over time. And you start with these nice, clean magnetic field lines from the top to the bottom, and then over time they get all twisted and turned out and not connecting sort of top to bottom. And then you get this point where it’s all jumbled, then it flips over and balances back out again. It’s quite amazing, and it’s…a lot of this kind of theory, this only came together fairly recently, I mean, we’re in modern history and the people really figured out what’s causing this cycle, the sunspot cycle, and how it connects the field lines and really what’s going on. It’s quite a fascinating process. And, I mean, there’s a version of it that happens here on Earth, although it’s different.

Pamela: Now, we don’t fully understand the time scales for the Earth. We just know the Earth does flip occasionally, but the Sun’s pretty much like a confused clock that is sometimes ahead and sometimes behind, but averages out to on time in the end.

Fraser: And so this is the situation that we talked about. So we are nearing the solar maximum in 2012/2013, and what does the solar maximum mean?

Pamela: Solar maximum is that point when the Sun’s magnetic field is its most tangled, when you have field lines that are poking through the surface, and when you see sunspots. The sunspots often come in pairs, and one of them is the point where the field line is coming through the surface, and other one is the point where the field line is going back into the surface, and as the field line twists itself around, it actually channels plasma, and so these footprints can be connecting plasma loops, they can be the cause of giant coronal mass ejections…all sorts of activity is associated with these places of magnetic entanglement. And when the field lines break, as they sometimes do, and rearrange themselves into lower energy configurations, that energy can get flung straight at us here on the planet Earth, so we actually really have to pay attention during solar maximum because, well, sometimes we get lucky we just end up with amazing northern and southern lights – the aurora borealis that you can…well, last week there was one that was visible as far south as Arizona. You only get that with big solar flares, but if you get unlucky, you’re not paying attention, when all that energy, when all those ionized particles hit the Earth’s magnetic field, they generate electricity in the Earth’s power grid, and this is something we’ve talked about in “Various Ways to Destroy the Earth” shows, and that excess energy in the Earth’s power grid isn’t exactly free energy. It is actually sometimes a cause for lack of energy because it can, well, overwhelm the system and take down the grid.

Fraser: And there’s, you know, those magnetic field lines coiling out of the sun – it’s a really powerful analogy in my mind, and you can see these amazing videos taken by some of the recent spacecraft — the SDO mission, right? You can see these videos, time-lapse videos of the surface of the Sun. And you see the solar material following the field line from one sunspot to another sunspot, and you can see how it’s sort of wriggling, like writhing, like snakes on the surface of the Sun, and then you can see them snap like someone has coiled up too far, and the, you know, the coil just can’t handle it anymore and it just snaps and releases, and you see this material flung out like the end of a whip, like a bullwhip, is being sprayed out into space, and then you can see the sunspots disappear. The videos, the time-lapse videos of the Sun, of the solar activity is just mind blowing. Some of those beautiful space-related video, like, time-lapse footage that you’ll ever see…I could just watch that stuff all day. So that’s the solar maximum. The solar minimum is this opposite situation, right? Where there are no sunspots, the magnetic field is not coiled. Is there like a great big sunspot at the north and south poles of the Sun where the magnetic field lines are coming out?

Pamela: [laughing] No. What’s actually kind of amazing is that during solar minimum, you end up with most of the sunspots at the equator, of all places, so as you hit solar maximum, you end up with sunspots towards more southern and northern latitudes of the Sun. They really only get as far north and south as about 30 degrees, but it’s still neat to watch them back and forth. And we’re talking averages here — sunspots can poke out anywhere they please.

Fraser: And you can have times where there’s not a single sunspot on the surface of the Sun.

Pamela: You can actually have months, occasionally years, with no sunspots at all, and this is one of the things that we’ve recently been dealing with. This was kind of the solar minimum that refused to end, and we’re still trying to figure out what causes this to happen sometimes. As you look at long-term maps of solar cycles, you see that there’s amazing variation, and sometimes the Sun just stops, and we don’t know why – for twenty thirty, fifty years. And one of the problems that we deal with is things like the modern minimum from 1650 to about 1700. That was a period of negligible sunspot activity. There were sunspots, but very, very few. And during that period, we actually had a mini-ice age where planetary temperatures dropped, where one of the problems associated with this is you end up with much stronger winter storms in New England and in northern Europe; you end up with much hotter seasons in the central regions of America and in Canada. Southern Europe is also hot. We don’t have as good of records for some other parts of the planet, and so when we see the Sun going into quiet times, it’s sort of a warning that, “Wow! We could have severe northern storms.” So looking at things like last year and the year before where it decided to just snow in England on a regular basis, there are those who attribute that random, non-normal snowing in England to it actually being a really quiet sunspot time.

Fraser: Hmm…interesting. I wonder if there is a larger cycle that could last over thousands of years, and maybe…that sits on top of that 22-year cycle of the sunspots coming, coming, going away, coming back that has these highs and lows, you know, more modern minimums, but the problem is that we’ve only been observing sunspots for the last few hundred years, and so we just don’t have any accurate observations before that.

Pamela: We do have hints at longer-term cycles, and the hints come from ice cores. One of the things about the sunspot cycle is it’s tied to the whole magnetic behavior of the Sun, and so when you have a really active Sun, you actually have the solar winds and other factors pushing past the planet Earth, and actually making it harder for things like cosmic rays to hit our upper atmosphere, and with fewer cosmic rays hitting our atmosphere, we end up with fewer aerosols. There’s also various chemical productions that we see in our own atmosphere as a result of interplay with space weather, and so when we take ice core samples, we can actually look back in time and get a feel for what the Sun has been doing over, well, thousands of years, and so there are those who study this and are saying that we’re actually heading back towards a cooling cycle with the Sun, where perhaps for the next 500 years, we’re going to slowly work ourselves down to a point where the planet cools off to a lot like it was during the Holocene period before it again begins to warm back up where we’re looking at a much longer, 1000s of years cycle.

Fraser: So isn’t the rise and fall of the solar activity what’s driving, like, things like the ice ages?

Pamela: In the past. Um, right now we have to worry about the effects of man on the atmosphere, and that’s a whole can of worms for an independent show.

Fraser: And that makes the whole thing more complicated, which is that you’ve got the inputs of man pushing against the activity of the Sun, and the whole thing is super-complicated and takes, you know, people who specialize in it to argue about it, so definitely not a can of worms we’re going to open on today’s episode, needless to say…you know, we understand that it’s complicated, so we’ll move on. So I guess there’s like a longer-term variation in climate that can be attributed to the solar activity, the solar maximum, the solar minimum and some kind of cycle over a long period of time.

Pamela: Right. So what we do see is due to solar activity, which is just one of many effects, but there are specific points, such as the mini-ice age during the modern minimum that can be tied directly to the sunspot cycle. What’s interesting is we can also see planetary heating tied to the sunspot cycle, and that has some interesting sociological impacts.

Fraser: I’m intrigued! Please tell me more about the sociological impacts.

Pamela: [laughing] So I have to admit I need to do more research on this because there’s statistics, and then there’s statistics that are really, well um, couched in what is the differentiation between this and random.

Fraser: Yeah, but you found some really cool research.

Pamela: I did find some really cool research. So one of the things that I think all of us know is that when you’re hot, you’re grumpy, and it turns out that when the planet is hot, societies get grumpy. And so there was a recent study coming out of the Earth Institute at Columbia University in New York that found that there appears to be a link between El Nino, which is a warming of the oceans that’s tied to warmer seasons, that, well, when there’s El Nino, there’s also a lot of world conflict, so they were able to tie roughly a fifth of world conflicts to warmer temperatures, so, yes, if you want a civil war, wait for an El Nino and it may just happen on its own.

Fraser: Right, so we’ve talked about sunspots and twisting magnetic fields, but there’s a lot of other really cool stuff that the Sun throws at us, like, we hear about flares, and coronal mass ejections, and solar storms, and proton storms, and things like that, so what are all these? Let’s kind of run through these. What are the kinds of things that the Sun can emanate during these periods of solar activity?

Pamela: So, solar flare is usually nothing more than…it’s a energetic outburst that probably isn’t going to destroy anything, or cause astronauts to have to go into hiding, or anything particularly exciting, but it’s just when a field line breaks, and a bunch of material is released into space, so this is…

Fraser: That’s that snapping that we talked about earlier…

Pamela: It’s that snapping, and all of that material that’s tangled up inside of that magnetic field, well, it just keeps going in a straight line along whatever direction it was heading in originally.

Fraser: But why do we see a blast of x-ray radiation?

Pamela: There’s some things we’re still trying to figure out. One of the things that has amused me in recent years is at the American Astronomical Society meetings, about every two years there’s a major press release on, “We have now figured out why…” and it’s going to be either coronal mass ejections, or why some parts of the Sun’s atmosphere are hotter than they logically seem to be, or any number of different things, and the x-ray emission comes from the high-energy particles that are tangled up in the magnetic fields, but that doesn’t explain all of the high energies that we see, so we’re still figuring this out. It’s awesome to have the stars so close to study, but when something gets studied in sufficient detail, you realize it’s a much uglier problem than you thought.

Fraser: Well, didn’t you say that solar hydrodynamics is the most complicated science and mathematics that you could possibly envision, that trying to understand how plasma works in three dimensions…?

Pamela: Yeah, it’s hydro-magneto dynamics.

Fraser: Hydro-magneto dynamics.…sorry, I forgot the magneto part.

Pamela: It’s just nasty.

Fraser: If you want to choose the most complicated path in science, in astronomy, there’s your career path.

Pamela: So the broad brush strokes answer is the magnetic field lines have a whole lot of energy in them, and when they break its because they’re rearranging into a lower energy state, and all that energy has to go somewhere and sometimes it gets thrown straight at us.

Fraser: [laughing] Right. Right. And so the solar flare is that momentary release of energy that is a blast of radiation. Um, the coronal mass ejections are these particles that are thrown out in some random direction — sometimes right at Earth.

Pamela: Now, so coronal mass ejections are basically the big, angry brother of solar flares. So solar flares are fairly well understood; they’re tied to magnetic field lines, they’re rearranging. Coronal mass ejections we’re still trying to sort all the things that trigger them. They’re also triggered at times by breaking the field lines, breaking the tangled up field lines, clusters of sunspots, and when these go off, we also can get a blast of particles heading towards us at various different velocities. So sometimes we’ll only get half a day’s warning that there’s this cloud of particles heading toward us, and sometimes it’s a couple of days, and these are the things that we do have to worry about because, well, all of those ionized particles, those can pose danger to astronauts. All of the high energy radiation tangled up with this –that can pose danger, well, to just about everything on orbit. Luckily, the light gets to us before the particles, so thanks to spacecraft like STEREO and SDO that are watching the Sun for us… SDO actually takes an image of the Sun every 10 seconds. These spacecraft are allowing us to do better modeling, are allowing us to see the stuff on our way, and as we continue to watch these things, it’s a matter of building up models, of “if we see this, then this is going to occur; if we see this, then this other thing is going to occur.” And between STEREO and SDO’s constant vigilance, we’re getting better at predicting when large solar flares are coming our way.

Fraser: That’s really cool. STEREO, you know, particularly has this 3-dimensional view of the Sun, so one of the big problems with a lot of the spacecraft before now was they took a picture of the Sun and they could see a coronal mass ejection, but they wouldn’t know if it was actually directed right at Earth, so they would say, “Well, we kind of probably think that maybe this one’s coming toward Earth,” but STEREO sees it in 3-D, so it can see the alignment of the coronal mass ejection and tell with a lot more accuracy exactly where that gun was pointed, and…

Pamela: And the way it’s seeing in 3-D is one of the two spacecraft is in an orbit that’s slightly bigger than the Earth’s, and the other one is in an orbit slightly smaller than the Earth, so this is causing them to lag behind the planet, and move in front of the planet and actually look at that space between the Sun and the Earth. Now, unfortunately…

Fraser: It’s binocular vision of the Sun.

Pamela: Exactly. Now, unfortunately, they’re eventually going to pass behind the Sun, which isn’t a useful place for them to be, but they come back around, and assuming these spacecraft are still healthy, once they come back around we’ll be able to use them again.

Fraser: Yeah, that’s amazing. And so we get this binocular view, so you get this chain, right? You get an X-ray flare, the spacecraft can spot the direction that the coronal mass ejection has been blasted out, and then predict that a storm of particles is going to pass by the Earth within “x” minutes because the light from the Sun takes 8 minutes to get here; the particles take only a little longer than that, and so the astronauts have a few seconds or minutes to get into cover before they sweep past the Earth.

Pamela: And most of the time the particles do take hours to days to get here, so that’s a good thing.

Fraser: But some of them can be really energetic and can get here really fast, and they’re worst ones, right?

Pamela: Yeah, it’s a difficult situation because the more dangerous, the less warning.

Fraser: So, we’re kind of running out of time, but I just wanted to compare and contrast what we see with our Sun with some other stars out there, and maybe this is a whole other show on its own where we can talk about solar activity or the star activity on other stars are, but how does our Sun compare to other kinds of stars? If we could get up close and watch, you know, Betelgeuse or a red dwarf star, or…you know what I mean?

Pamela: Right, so we do see other stars, Betelgeuse being one of them, that have much larger sunspots that – well, we don’t know for certain if it’s individual sunspots that are much larger, but have large percentages of the side facing us covered in sunspots, so we’re able to map over time using interferometric telescopes the patterning of the sunspots. This is one of the amazing things that we’ve started to be able to do by linking together multiple optical telescopes is actually tell how sunspots appear on the surfaces of stars that were just able to resolve. We’re also able to look at minor variations over time, and using high-speed imaging start to get hints at, well, this is actually a variation that goes with the rotation period of the star. Well, that’s likely sunspot behavior as well. We also see violent, violent flares from some types of stars. The type of flares that would just casually destroy our atmosphere on a regular basis, so we both have more run-of-the-mill sunspots; we also have much less flare activity, and all of this makes our planet a fairly safe place to be. Now, this has a lot to do with where we are on the diagram of stars — we’re not too cold, we’re not too hot, we are happily burning hydrogen…all of these things are good things to be doing.

Fraser: Right. But we could have things a lot worse …

Pamela: We certainly could.

Fraser: …as far as stellar activity goes, but then we wouldn’t be here to talk about that, so there you go. Alright, awesome! Alright, well thank you very much, Pamela, and…Oh, just one last thing just to mention is one of the big side effects of all this solar activity is the auroras that we see here on Earth, and so we’ve done a whole episode just on auroras that you can listen to that gives you a lot more information on exactly what’s going on, exactly how the interactions are with the Earth’s magnetic field, and how you can see them, and so on…So we are, as we said, we’re entering this period of high activity and over the next few years, we’re going to have multiple opportunities to see auroras, and if we’re lucky they’re going to be fairly far south, so stay tuned to spaceweather.com. They probably have the most comprehensive alerts, and anything that’s going to be really interesting, we’ll mention it on Universe Today, but definitely try to go out and see some auroras over the next couple of years because then you won’t be able to see them again for a long time.

Pamela: And in general, the best aurora curve, for whatever reason, of the alignment of the magnetic fields around October and March of each year, around the equinoxes, and so in the couple of months around equinox, that’s when you really need to stayed tuned to, “Oh, there’s a solar flare! Oh, there’s a coronal mass ejection!” Good chance of good aurora.

Fraser: Yeah, get outside, take some hot chocolate, stare into the sky and hope that you’ll be able to see it because if you do see an aurora, it’s one of the most amazing things that you’ll have ever seen in your life so, and you know, some of them have gone really far south; I mean, I remember hearing with a storm people were seeing them in like Florida, so it’s not impossible with this solar cycle.

Pamela: And one of the amazing things is you can actually see them from spacecraft, so if you’re flying Trans-Atlantic or trans-pacific where the airplane is likely to cut near one of the poles, try to sit on the side of the aircraft that’s going to put you on the pole-facing side, so Chicago to London sitting on the north side of the plane, Cape town to Sidney sitting on the south side of the plane, and you’d be surprised. I saw some absolutely amazing aurora a couple weeks ago on a flight over to London.

Fraser: Cool pro tip! I love that! OK, well, thanks a lot, Pamela. I know you’ve got to run to a flight. Thanks again, and we’ll talk to you next week.

Pamela: Sounds good. Talk to you later, Fraser.

Transcript: Spooky Space Sounds

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Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University-Edwardsville. Hi, Pamela. Happy Halloween!

Pamela: Happy Halloween! How are you doing today?

Fraser: Doing really good. We’re going to go into a whole pile of trick-or-treating tonight, but uh…or I’m imagining in the future; we’re actually not recording this on Halloween, but to get into the setting…but yeah, our kids are at that age now where Halloween is a competitive sport.

Pamela: That is awesome!

Fraser: It’s all about speed and endurance and starting time, and uh, yeah….

Pamela: That is very cool. I live in a small town, and we actually do a town Halloween parade, where it’s a bunch of, basically, take someone’s old hay trailer and build a float on top of it and pull it down the street with a tractor or a pick-up truck — and it’s really endearing, and they throw candy at the kids, not to the kids, at the kids.

Fraser: Wow, Halloween’s a big deal, then?

Pamela: Oh yeah, totally. We actually have a neighborhood email list to get competitive on who gave away more treats.

Fraser: [laughing] That’s awesome! Alright. To help you out with your Halloween party, we’ve collected together the spooky sounds of the Solar System. Every piece of audio you’re about to play might sound like it comes from a terrifying nightmare dimension, but it’s really just a natural space phenomenon right here in our own solar system. Alright, Pamela, so this show’s going to be a little different in that we’re going to play a bunch of audio clips, and then we’re going to explain the science that’s going on. So why don’t we just listen to our first clip?

Pamela: OK.

[audio clip]

Fraser: That was really weird. That kind of sounded like an underwater depth gage, like a submarine sound…so what were we hearing there?

Pamela: So the background hissy static — that’s just the sound of the sky. It’s the exact same thing you see when you turn on a television, not a new digital television, you have to find one of the old, regular televisions, and you turn it to someplace where there’s no channel. It’s that background radio photons that are coming from space, that are coming from electrons trapped in the atmosphere, just the hum of electrons changing energy levels and in the process giving off radio light. Now, that high-pitched UFO noise you heard, that was actually the sound of a meteor reflecting back off of its ion trail, reflecting back sounds from an earth transmitter. Our planet’s covered in, well, radio-transmitters; they’re giving off your radio signals, they’re giving off your television signals, and as a speck of rock comes through our atmosphere, it heats up, it charges the atoms around it as it goes through the atmosphere and it leaves this trail of excited atoms behind it, and that trail of excited atoms acts like a mirror and sends back some of that radio emission, and creates that UFO noise that you hear above the background hiss.

Fraser: And so if they were recording for a whole night, you would be able to hear every meteor that was going across in the sky.

Pamela: And what’s kind of awesome is that clip was from the Geminid storm — and you can actually do this for any meteor storm, you can go out, get a radio receiver that’s tuned to the proper station (and there’s instructions for how to do this on-line that we’ll link to in our show notes), and you can sit there and you can watch the sky for the shooting stars, and at the same time, listen to the noise they make as they reflect back bits of radio signal.

Fraser: And so it’s science that regular people could do with a little bit of investment and some time and work. It’s not…you don’t need a huge radio dish.

Pamela: No, this is the perfect science fair project if you’re looking for a science fair project for your kid and you have a Radio Shack nearby. It’s really something awesome that everyone who has a kid who likes to tinker should do at least once while their kid is growing up.

Fraser: That really sounds like a UFO. That was great! OK, let’s do the next one.

[audio clip]

Fraser: Alright, so that sounded to me like a bit like sirens off in the distance, police sirens off in the distance, a whole bunch of them, or people playing the saw — you know, that sound, you know, when you play the saw, or a bit like crickets, like cicadas at night. So what was that?

Pamela: That was actually the solar aurora. That was magnetic interactions between our Earth’s magnetic field and particles from the Sun that if you could go out and look at them would probably paint the sky in fabulous dancing curtains of green, but auditorily, when you take the radio emissions and you play with them to get them down to where a human can hear them, those particles from the Sun when they hit the Earth’s magnetic field, they change velocity and that change in velocity is a change in energy, and that energy has to go somewhere, and that energy goes into creating radio signals, release of photons in the radio frequencies, and we’re able to detect those using very special, not-so-cheap-and-easy-to-build-in-your-backyard, using special radio receivers, and what’s neat was the person who recorded this, Stephen McGreevy, he actually he went on a trip up to Grassriver Provincial Park in the central western Manitoba area of Canada and this was during normally solar minimum, but there was a really nice light show back in the summer of 1996, and as he looked at the aurora straight overhead, he was able to capture the sound coming from the aurora at the same time.

Fraser: That’s pretty amazing and it’s interesting that it happened during the solar minimum so I wonder if someone’s going to be doing that now that we’re nearing the solar maximum.

Pamela: Well, what gets me is so you can have solar flares at any time, but the type of sound that you get from them captured in the radio signals – that traces out how the particles are interacting with our magnetic field, and if you have a whole lot more particles coming from a really big flare, like the flares we’re starting to get right now that are causing auroras visible as far south as Arizona, they’re going to be even more spectacular to listen to, and I look forward to seeing those posted on the internet — they’re just not there yet.

Fraser: OK, so let’s move on to the next one, and it’s kind of related…

[audio clip]

Fraser: That’s a haunted house.

Pamela: That’s totally haunted house. This is the one [missing audio] sent me. It’s totally haunted house!

Fraser: It is amazing! Alright, now we’re getting into it. I mean, that was a haunted house sound. That was really scary! What is that?

Pamela: That’s Saturn!

Fraser: What part of Saturn?

Pamela: It’s an aurora on Saturn. It’s basically the big brother to the previous sound clip that we listened to. So the Cassini spacecraft is approaching Saturn; it was able to listen in on the Sun’s, well, solar storms wreaking havoc, or at least wreaking beautiful noise on Saturn’s magnetic fields. So as waves of particles went in and moved up and down the field lines, their changes in velocity and other interactions were able to produce these changing pitch radio frequencies and the change in pitch, that actually corresponds to the different energy levels, where as you’re hearing higher pitched notes, those are higher energy, higher frequency photons, and as you hear the lower pitches…so you’re essentially sliding up and down the energy spectrum. Think of it as particles sliding down the magnetic field and gaining and losing speed depending on which direction their whipping along the field lines.

Fraser: Right, and it’s…I mean there was something in common with the Earth aurora, but it definitely sounded otherworldly. Is it just like the instruments that were used to measure the two different aurora?

Pamela: It is a matter of: this is a much better instrument. It has much better frequency coverage, which is where you get the sliding up and down, so if you imagine a difference between a slide whistle that is two inches long and a slide whistle that is twenty inches long that allows you to detect different things. It’s a difference in, well, you’re not getting all the background hiss that you get from being within the Earth’s atmosphere. And then it was just they managed to take a much longer time and they cheated. In that particular audio clip they seriously cheated. Every 73 seconds of audio corresponds to 27 minutes, so they sped things up a little bit, which helps as well.

Fraser: Right. That’s what I was wondering is: was that over a long period of time? OK, so let’s move on to the next one, and just give people a hint: this is also on Saturn, but something different.

[audio clip]

Fraser: That sounded like hail hitting like a tin roof, but a little more muffled, or like you’re walking on chunks of ice, or walking on snow, like icy snow.

Pamela: Or, so I don’t know if you’ve had this where you are, but here in southern Illinois, and back growing up in Boston, we’d sometimes get these snowstorms that would cover the roof and everything else in 5, 6, 10 inches of snow, and then we’d get an ice storm afterwards, so you end up with this layer of ice on the top of the snow, and the sound of the ice balls hitting the snow sounded a lot like this as well.

Fraser: I mean, we never get anything like that, but… So what is it then?

Pamela: That is lightning on Saturn.

Fraser: Are all those pops like lightning strikes?

Pamela: That’s lightning bursts. Yeah, so you have, basically, you’re catching all of the lightning strikes across a large section of the planet. You hear all of these little tiny pops that are all different frequencies, and they’re occurring over time (again this is one that’s sped up 20 seconds in this case is 2 hours, so you can imagine each of those little blips is lightning that occurred over two hours). But this was a massive lightning storm, and we can also detect the Earth’s lightning, but it doesn’t sound like much when you add in the Earth’s noise that we also receive, so this was just much more amazing. And we don’t really think of Saturn as having lightning storms — it’s not like we see lightning bolts when we look at pretty, astronomical images of Saturn, but this is a stormy planet that has lightning going off all the time, and we can detect it from its radio signals.

Fraser: Alright, let’s move on to another one and this one is still — like we’re following a theme — it’s lightning, but it’s somewhere else. Listen.

[audio clip]

Fraser: I’m hearing a video game. It’s sounds very familiar. I think I’ve played that game.

Pamela: Either that, or like a bad 1980s sci-fi battle scene.

Fraser: Yeah, exactly! Perfect. So, I said it was lightning. So where is this?

Pamela: This is here on Earth, but we’re listening to something else now. We’re not listening to the individual bleeps of lightning like we were on Saturn. These are what’s called whistlers, and what ends up happening is when you have the lightning go off, it can produce ionized gas, and that ionized gas as it gets caught up and travels along field lines, produces this whistling noise. So again, lightning, but you’re hearing a different aspect of the lightning, and this is just one clip of many that we could have chosen from. You get them that they sound sometimes like an entire arcade of video games because you get different ones going off at different frequencies all layered on top of each other. So here is ionized gas that is created by lightning and produces radio signals as it travels along magnetic field lines.

Fraser: But it’s the same phenomenon — that’s really neat! Alright, let’s move on to another one.

[audio clip]

Fraser: Right, so that one sounded similar to the haunted house sound, but then there was like this crash halfway through.

Pamela: Right, so it’s sort of like you’re going along, they’re trying to creep you out, they’re trying to creep you out, and then they attack you with everything all at once! In this case, it’s the Cassini spacecraft again traveling through space, listening to radio waves, listening to radio waves, everything’s fine, suddenly hits the edge of Saturn’s magnetic field, and that place with the solar wind hits the edge of the magnetic field. This is the bow shock region around Saturn and everything goes nuts at that particular place. One way to think of this is it’s almost like the sonic boom that’s created when you start traveling faster than the speed of sound, and it booms through. This is the radio in the magnetic field equivalent of that, so you have supersonic solar wind suddenly gets decelerated rather rapidly and creates this pulse of radio emissions across the entire frequency band.

Fraser: It’s the same instrument that captured the sounds of the aurora, which is why it sounds familiar, but it’s capturing a different phenomenon at this point. I mean, we’ve all seen those pictures of a bow shock. Usually we see it around the Earth; we see these illustrations of it. It almost looks like there’s a comet around the Earth, where on one side of the Earth, it’s rounded — and this is our magnetic field, and then on the other side of the Earth, the one that’s away from the Sun, it’s stretched out into this big, long tail because that’s the side that’s not being impacted by the charged particles from the Sun, and that’s the thing that’s protecting us, and I guess protecting Saturn, and this is that moment where Cassini crossed into that force field around Saturn, right?

Pamela: And it wasn’t the fact that Cassini crossed it so much that caused the sound, as Cassini was able to hear all the solar particles that were traveling along with it have the “Holy expletive!” moment of changing velocity, and this is something that we keep kind of saying as though everyone understands it, but all of these noises come from some sort of a particle: an electron, a proton, an atomic nuclei that doesn’t have as many electrons attached to it as it should. It comes from one of these charged particles traveling through space and interacting with a magnetic field in a way that changes what direction it’s moving in, it changes what speed it’s traveling at, and all of these different changes represent a change in the energy of the particle. And when you change the energy of a particle, that energy that it lost has to go somewhere, and where it’s losing the energy is into creating radio light, and so if you think of it in terms of: if you get something going really fast, it has to take energy from somewhere – that’s the gasoline, and then when you slow it down really fast, slam on the brakes, the tires get really, really hot from all of that energy that had been the motion of the car getting expelled against, well, the asphalt as the tires try and screech to a slow-down, so what becomes hot tires, when it’s a slowing down particle, becomes radio energy instead.

Fraser: Right, or to use another analogy, right, if you’re not wearing your seatbelt and you run into something and you come smashing out the front window, you’re the radio emissions being given off by the car, which is the particle, so…alright well, the next one then is similar, but a different spacecraft.

Pamela: Yep.

[audio clip]

Fraser: That one was a little more subtle. What were we hearing there?

Pamela: Those were what are called electron plasma oscillations, which is a fancy way of saying there’s a whole lot of charged particles out there, and as those charged particles from outside of our Solar System hit the termination shock of the solar particles pushing against them, they end up getting driven into oscillations, and the Voyager spacecraft, as it’s trying to leave the Solar System, has had this weird experience of the solar termination shock. Where it ends depends on how active the Sun is, so it goes back and forth like where the shoreline is on a beach. As you’re walking along, sometimes your feet are dry, sometimes your feet are wet. Well, sometimes Voyager for a while was within the termination shock and sometimes it was beyond, and as it was traveling along, it got to pick up all of these little electronic plasma oscillations along the edge of that, well, termination shock to our Solar System.

Fraser: And so the termination shock is sweeping past Voyager and then coming back in.

Pamela: And beyond the termination shock is where there’s a region of electron plasma that is oscillating, and those little blips of noise that you hear — those are the plasma oscillations. Now, the reason it doesn’t sound quite so sexy as the other ones is — it’s Voyager.

Fraser: Right, it’s a very old spacecraft, very far away, not able to send a lot of data, not a lot of power…

Pamela: [laughing] Right.

Fraser: You can barely hear it…yeah.

Pamela: Yeah, so it’s several hours worth of data…collapses down into like six seconds of audio, and the frequency range that we were listening to was a lot less than some of the other clips.

Fraser: So, when Cassini…well, Cassini will never get a chance to leave the termination shock, but if it could it would sound different. We would hear a more high fidelity version of this.

Pamela: So hopefully someday we will get to send an instrument with the fidelity of Cassini out there, but it’s not in the budget right now.

Fraser: So, let’s do our last piece of audio.

[audio clip]

Fraser: I heard a saw going, you know, going through metal really far away, or some bird, some exotic bird in the middle of a rainforest making its sad call, but what are we hearing?

Pamela: What I heard actually was a 1980s synthesizer pretending to either be a piccolo, or a bird and failing miserably in the process. The reality is we were listening energetic electrons at Jupiter caught up in its magnetic fields. Jupiter is one of the most complex magnetic fields in the Solar System in terms of…well, it has a nice, normal magnetic field that has moons embedded in the side of it, and those moons spew up particles that get caught in the magnetic fields, and some of them have their own magnetic fields and, well, to the hapless electrons out there, they can what are called cyclotron emissions as they move through the magnetic fields and spiral rapidly around and around the field lines, and in the process they give off radio emission that sounds rather like you wish you were wearing earplugs.

Fraser: Well, this is Jupiter’s equivalent of a particle accelerator.

Pamela: Exactly, and it’s one of the biggest particle accelerators in the Solar System. It’s just not useful for doing, well, Higgs Boson-type science.

Fraser: Yeah, um, the power would be there, we just can’t control it. Right. So that was great. Now, that’s actually only about half of the spooky sounds that are out there. We just covered the ones that we have in the Solar System, so maybe next year, we’ll cover the spooky sounds around the whole universe because there’s pulsars…

Pamela: Blazars, and quasars …

Fraser: Quasars and all kinds of great stuff, so I hope you enjoyed this, and I would love to hear if anybody wants to turn this into a haunted house background sound. People could play it in their homes, “What’s that weird sound?” The sounds of space…

Pamela: And we have to give kudos to the University of Iowa for putting these up on their website. This show was made much easier to put together thanks to the hard-work of the folks there just archiving these noises and making them not sound horrible to the human ear.

Fraser: And I know you kind of curated this one with your friends on Twitter, so thanks to everybody on Twitter who responded to you and pointed you towards cool, spooky space sounds.

Pamela: So one final announcement before we disappear. I was asked by Andy Shaner at the Lunar and Planetary Institute down in Houston, TX if I could let all of you know about a project called “My Moon.” They’re actually trying to provide jobs to people 18-25 who are interested in the Moon, and are interested in helping them out with the Moon, and if you want to find out more, we’ll be tweeting about it and we’ll post a link up on the website, or you can just Google “my moon street team” and find out how you can be a part of, well, helping everyone know more about the Solar System.

Fraser: Sounds really great. OK, well, thanks a lot Pamela! We’ll talk to you next week, and Happy Halloween!

Pamela: Happy Halloween!

Transcript: Weather

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Fraser: Welcome to Astronomy Cast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain, publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi Pamela. How are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: I’m doing great. Now, I know you wanted to pump up the store today.

Pamela: Yes. It’s actually t-shirt season, even in like the places where it refuses to ever stop snowing, it’s starting to be t-shirt and giant mosquito season, and while Astronomy Cast t-shirts will not protect you against mosquitoes, you will at least look really good and nerdy while you’re getting eaten by the bugs, so go buy a t-shirt.

Fraser: I’ve had lots of people stop and say, “Cool shirt! What’s Astronomy Cast?” and then I have a new listener, so…yeah, definitely, if you wear the shirt, you have the responsibility of promoting the show, just so you’re clear.

Pamela: But you’ll look cool.

Fraser: But you’ll look super-cool and people love the shirt. So how could a person purchase these wonderful items?

Pamela: Well, that’s a wonderful question, Fraser. So all you have to do is go to astrogear.com will get you there, and we have not just t-shirts, but we also have pins and CDs and posters, and all the proceeds go to paying the happy people that make the show go that aren’t Fraser and I, who do this because we love you all.

Fraser: Yeah, yeah, we don’t get paid. [laughing]

Pamela: [laughing] …but we have Joe who helps keep everything up-to-date on the websites, and Nancy Atkinson, and a woman named Romayne, who does the transcripts…

Fraser: Preston…

Pamela: Preston, Preston…Preston is awesome, and he’s the reason you hear us right now.

Fraser: Correct.

Pamela: …and we want to pay them, so buy t-shirts and look awesome, please.

Fraser: Alright, let’s get on with the show then. So, how’s the weather? Well, maybe a better question is “why’s the weather?” What is it about planets and their atmospheres that create weather systems? What have planetary scientists learned about our Earth’s weather, and how does this relate to the other planets in the solar system, and what is the most extreme weather that we know of in the whole universe? Alright, Pamela, so why’s the weather?

Pamela: Because there are thermal gradients.

Fraser: So if we were gonna like, “Webster’s dictionary says…” what is the weather?

Pamela: [laughing] So the weather is the change in various atmospheric properties: humidity, dense pressure — all of these different things as a function of altitude, as a function of time, as a function of where you are located on the planet.

Fraser: And as you said, it’s thermal gradients that because thermal gradients exist, because there are differences in temperature at different places in the atmosphere, we get weather.

Pamela: Exactly. It all comes down to the Ideal Gas Law at a certain level because as you have variations in temperature, it causes the gas to contract, expand, depending on what that change in temperature is, and if you have a gas contracting, well, more gas is going to flow in, it’s a giant system, everything’s connected. If you have the gas expanding, it’s going to push on things. And all of this has an effect: it drives wind, it drives floes; you can have changes that cause snow, cause rain, cause tornados (if you’re unfortunate), and it’s all about that difference in temperature from one place to another.

Fraser: And so you’re getting these differences in temperature from one physical location to another one, you’re getting these temperature differences depending on altitude, so you could be at one place and it’s warmer, higher up and it’s colder. So, what is the cause of these temperature variations (he says, knowing the answer)?

Pamela: [laughing] Well, at the most fundamental level, the sun is only on one side of the planet a given moment.

Fraser: And so that is the fundamental driver of all of these variations.

Pamela: Right, and this is why all the different planets have some sort of…if you took a planet and you were able to quite happily put it inside of a star sphere where every single point received the exact same amount of illumination…

Fraser: But why would you do that?

Pamela: Because you could get rid of the weather!

Fraser: Well, good! Alright, and the planet…

Pamela: Well, if it was a sufficiently large enough sphere…[laughing]

Fraser: Fine. No problem, you go ahead, put your planet in your atmosphere and see how that works out for you.

Pamela: So, if you were able to create this artificial “sphere-o-star” and make it sufficiently large so to not fricassee a planet, and you were able to take that planet under constant illumination, and just sit it there and have constant surface features so every place on the planet absorbed and emitted light in exactly the same way, then you could have a weather-less planet, but as long as there’s any variation anywhere — even in that “sphere-o-star,” if your planet was white on one side and black on the other, that would be enough to drive some sort of weather in the atmosphere.

Fraser: Or if there were mountains, or you name it. OK, alright. Well, we kind of have some planets, though, in the Solar System, well, we have one planet that doesn’t experience very much weather at all: Venus.

Pamela: Well, Venus pretty much does have constant misery, but that constant misery that it experiences, you see in the cloud patterns of the winds, you see these banding jet streams, you see the vortex at the poles — all of this is driven by…there are thermal gradients in this overall misery that is the planet Venus.

Fraser: Alright, so back to Earth then, so we’ve got these temperature gradients, we’ve got differences in location depending on where the Sun in shining, we’ve got differences in altitude about how high up in sea level you are, and also just differences in latitude, right? If you’re more north, you experience less sunlight, and if you’re in the south, or if you’re near the equator, you experience more sunlight, and then I guess as you get down to the southern pole, less sunlight, so what does this turn into for our planet?

Pamela: So we have the major thing that dominates our weather is the difference between tropical heating, so this where between roughly Florida and the southern equivalent of where Florida is located, which is part-way down Africa: tropical band, and within the tropical band, lots of sunlight, lots of heating, oceans get much warmer because of all of the heating, and this one temperature extreme. Then, at both of the poles you have very, very little sunlight, some parts of the year, pretty much no sunlight at all, and that’s a very, very cold region of the planet, and this difference between the two regions sets up what is called the jet stream, which is the predominant blowing wind at higher altitudes, and in fact hurricanes are what happens when the jet stream behaves badly.

Fraser: And so you can kind of explain all of the weather systems, you know, the jet stream is some of the big ones, but then we see these small, localized weather systems…you know, we’re having a particularly cold spring here.

Pamela: Right.

Fraser: What’s driving that?

Pamela: So I have to admit I don’t know exactly what is driving Vancouver right now…

Fraser: No, no, I mean, no, but just, in general, the local weather conditions, right?

Pamela: So local weather conditions — what you end up with is things like long lasting snow cover, that’s an Albedo difference, and that’s an insulating factor, so rather than letting nice, dark land heat up and trap in the heat which is part of why the hottest days of summer lag behind the longest day of summer, so without getting all of your snow melting, which I know is a problem you’re having, the snow that is still there is able to not let the land warm up, and not let the land help warm up the air. You also can end up with local oceans trapping in more cold, and again, this is in this case, it’s not a heat reserve, but it’s a heat sink, so energy that might not otherwise be needed to help heat up the waters…still needed to heat up the water. You can end up with all sorts of local effects that also depend on how much foliage is around, so maybe the farmers planted something different or maybe the roofing materials have changed. All of these different things can have effects that aren’t necessarily anticipated when people are necessarily choosing what crops to plant and inadvertently changing the local regional temperatures.

Fraser: And so then how well do scientists understand the weather process? I mean, you know, they always say that predicting the weather is an inexact science. I think that’s kind of giving it…that’s generous.

Pamela: [laughing] That’s true. We’re starting to get to the point that five days out at least using the set of satellites that we have over the North Americas, we’re able to say fairly well, “OK, really, really bad (expletive) storm coming. Prepare to hide.” They were able to actually give with the massive band of tornadoes that recently went through the American South, they were able to give several days warning, that something really, really bad was coming. So we’re able to look at the planet, we’re able to look at the high pressure zones, the low pressure zones, we’re able to know the ocean is containing this much heat, we’re able to know the land is containing this much heat, and run complex computer simulations that takes into effect all of the topography and all of the atmospheric conditions and say, “Five days out, roughly, what’s coming, but beyond that, it starts to get too difficult, and things break down very quickly.

Fraser: Do you think that they’re, I mean, are they going to be getting better at this? What’s needed?

Pamela: The problem with weather is it’s a chaotic system, which means that slight differences of maybe a degree, of maybe a couple of new skyscrapers, of maybe just a boat blowing its horn, those slight differences, the butterfly in the wind that you’ve always heard about on TV — those things cause huge effects that blow up over the timescale of about a week. So it’s the rate at which the errors in our measurements double, and it’s not the fact that we’re making errors in our measurements, it’s the fact that there’s chaos in our measurements that we can’t say the drop in Jurassic Park is going to go to the left or the right, so without being able to control our weather better, we can’t predict our weather better.

Fraser: I mean it’s kind of surprising that when you think of the movements of the Earth around the Sun are known within centimeters, you know, the, I guess, the angle of the Sun’s radiation hitting us is known, the amount of radiation coming out of the Sun is known, the topography of the Earth is known, the amounts of cover in ice and all that is all fairly known…it’s interesting that the chaos comes in there somewhere, you know?

Pamela: And part of the problem is trying to take into account of all of the little moving heat sources, and so think about something as simple as trying to keep an auditorium at a convention center at constant temperature. If you arrive for some sort of a large, plenary speech — say you’re going to hear Steve Jobs announce the latest, greatest whatever-it-is from Apple (that I know I will probably purchase because I’m just that type of a person) — if you show up early, the auditorium that might hold a couple thousand people is going to be frigid cold, but by the time everyone gets into the room and everyone flips open their technology or their technologies — and all those little things are heat sources — that room is going to end up overheating, and people going to end up taking off their jackets and loosening their ties, trying to deal with the fact that that once frigid room, which is now filled with all these little tiny heat sources, is now a much warmer room. And so, OK, you want to compensate ahead. You need to figure it out: how do you pace this system? It starts to become very complicated because you have to figure out something as stupid as: how many pieces of technology that produce how much heat are people going to bring with them? Because compensating for a MacBook Pro, which is a really good space heater in winter vs. compensating for an iPad, which won’t keep anything warm – those are two different problems. Now, that’s just an auditorium…now, if you’re instead trying to figure out how to compensate for understanding intricacies of the weather over a city, you have to be able to deal with such things as: well, how many aerosols are going to be produced by all of the cars, by all of the airplanes? We saw during the days after “9/11” massive changes in cloud cover just because there were fewer airplanes, so the simple act of saying, “OK, there are thunderstorms over Louisiana, let’s send all the airplanes north,” — that’s going to change the weather.

Fraser: But there were variations in weather before there were humans. You’re not saying, you know, it’s not our fault.

Pamela: No, it’s definitely not our fault, but you still have to be able to take into account all sorts of random things. There’s always been forest fires, there’s always been just herds of buffalo [missing audio] a field that has been completely eaten down by sheep vs. a field of knee-high prairie grass — those are going to impact the weather.

Fraser: Right, plankton blooms, volcanoes…

Pamela: Volcanoes seriously impact everything.

Fraser: Yeah, big snowfalls, I mean it all…it goes on and on, flooding…so, yeah. So then, what lessons, I guess, have the scientists learned about the weather we see on Earth and then compare it – what kinds of weather do we see on the other planets? Obviously, we need an atmosphere, so Mercury is out, and Venus is surprisingly out because it just has very little weather.

Pamela: It has very little differentiation in its weather. It has wind.

Fraser: Very little temperature gradients. It has horrible sulfuric acid rain, and other nasty stuff.

Pamela: So the types of things that we’ve been able to look at and understand are when we look at planetary atmospheres, you’re dealing with differences in heating on the two different front and back sun-facing/not-sun-facing sides of the planet, and you’re dealing with the fact that the surface of the planet is rotating underneath the atmosphere, and so you have energy going into the system, and this chaos of differential rotation — because the equator is going to be rotating much faster than the pole and what this ends up doing is setting up cells in the atmosphere — and so when you look at planets like Jupiter, this banding of the cells is extremely obvious, where what you see are these beautiful stripes around the planet, but what each of these stripy bits actually are is just areas where you have circulation in the atmosphere where on one side of that band, hot atmosphere is rising, and on the other north-to-south side of the band, the cold air is sinking, cold atmosphere is sinking, and so you have the bands north-to-south going through different circulation while also rotating around and around and around the planet in an east-to-west sort of direction.

Fraser: Well, aren’t they going like in opposite directions?

Pamela: And that’s one of the cool things is different bands do alternate in which direction you’re going, and we have the same thing on the planet Earth to a certain degree. We have far fewer bands so we don’t really notice it, but what we have is the Hadley Cell down toward the equatorial region, and the Ferrel Cell up above that and with the middle latitude Hadley Cell, you have this general I’m-gonna-track-slightly-south-and-west behavior, whereas with the more northerly Ferrel Cell, you have an I’m-gonna-track-east-and-north direction.

Fraser: Right, you get a situation like Jupiter where it’s a perfect environment. There’s a much higher temperature gradient between the center of the planet and space — you’ve got no land masses to stop anything from happening, you’ve got massive gravity, and you know, so you can see that that’s sort of in the perfect situation, you can even see it on the Sun, right?

Pamela: Yeah, exactly. You have convective cells on the Sun, and what’s kind of amazing about the Earth’s atmosphere is the atmosphere itself really extends more than 600 km up, but weather itself for the most part, is confined to just the first 15 km! And so just the very small, small height of our atmosphere contains all the interesting stuff that’s going on, and, in fact, in winter, the interesting bits end up getting stuck even closer to the Earth because the cold air, of course, contracts, and you end up with the atmosphere shrunk even closer to the surface of the planet.

Fraser: So where else do we see weather in the Solar System?

Pamela: I think some of the most interesting weather that we see, in some regards, is the planet Titan, which has, like Venus, cloud cover above it, but we know from some of the images from the Huygens probe that there’s definitely all sorts of fluvial, fluid-based geography beneath, so we think that these methane clouds are raining out methane rain that’s leading to methane rivers on this world where methane is at its triple point that allows it to be liquid, solid and gas.

Fraser: And — same situation — you’ve got the Sun heating Titan from one side, and then Titan is rotating, or is orbiting Saturn, and so, you know, sometimes it’s showing one face, and other times it’s showing another face, but it’s also….

Pamela: …blinking in and out as it goes into eclipse every once in a while, too.

Fraser: Yeah, yeah, exactly, and so you can see…and also it gets closer and further away from the Sun depending on whether where Saturn’s on its orbit, so you can see that some of these changes are pretty dramatic. And how extreme is the weather on Titan?

Pamela: This is one of those things we’re still trying to learn. It’s unfortunate we’re essentially looking strictly at the tops of, well, opaque clouds, so there’s been various return signals when we’ve tried to send different wavelengths of light through the atmosphere of Titan that have led us to believe that there’s rain going on, but we only have a few years’ worth of data and it’s not a lot of data, and…wouldn’t it be glorious if we could put a weather satellite in orbit that would be constantly returning IR images, constantly returning radar returns, and allow us to really get a sense of what was going on?

Fraser: First spacecraft to orbit Titan…yeah, that’d be alright.

Pamela: I’m good with that one.

Fraser: Yeah! So, what about Mars, though? I mean, I know Mars has got some really interesting weather.

Pamela: Yeah, Mars…it’s not the type of weather that we’re used to thinking about. We don’t think of dust as weather, but the reality is that with Mars the planet will undergo these massive almost entirely planet-wide dust storms. We’re still trying to understand what triggers them; we know that they’re seasonal. We also see that the icecaps — they grow and recede from season to season just like we see our own ice grow and recede, especially now with the North Pole here on the planet Earth. We see that exact same growing and shrinking, but what’s interesting is the growing and shrinking there actually affects the thickness of the atmosphere because the ice goes straight from being large, white, splotch — beautiful from a ground-based telescope, even a nice 14-inch will let you see the poles of Mars — to instead being an almost invisible polar cap, and a much thicker atmosphere.

Fraser: But you can just imagine, I mean, there’s got to be some really interesting process that cranks up the wind across the whole planet and kicks that dust up into the air.

Pamela: And even when it’s not massive dust storm season, we’ve caught on images from the Mars exploration rovers dirt devils just like you see racing across the American Southwest. Dirt devils!

Fraser: Well, they were cleaning up the rovers!

Pamela: Exactly. Exactly. And what’s amazing is some of the high-res images…you look down and you see these crazy paths of exposed lower-level dirt on Mars, and it’s just like, “what the heck caused that?” And then you realize that what you’re actually seeing is the path of destruction of a dirt devil.

Fraser: Yeah, that’s great…so it’s the same process, right? You look at Earth, you look at Mars, you look at Titan, you look at Jupiter – all the same process going on. What about places like Pluto, I mean, I know that Pluto has a bit of an atmosphere during its summer, right?

Pamela: Right, so what happens with Pluto is it’s not so much that the polar caps sublimate and make an atmosphere, but a certain amount of the entire planet…well, we don’t know if it’s the entire planet…we don’t know if Pluto’s…we don’t know that much yet.

Fraser: I wish there was a mission going there right now.

Pamela: You know there just might be. I think it might [missing audio] like New Horizons or something?

Fraser: Come on 2015!

Pamela: So we don’t entirely know what’s happening, but what we do know is part of Pluto’s surface sublimates and becomes a very thin atmosphere that causes stars that are getting occulted by Pluto to flicker as they get ready, and you see a change in the brightness, the change in the light of the stars, and what’s neat is while the date for this episode is quite a while in the past because we are trying to catch up on back episodes right now, in June of 2011, there’s going to be an occultation visible for different parts of the planet of Pluto, so Pluto’s going to pass in front of a star, and right now it’s entering its summer months (or summer years as the case may be), and so, hopefully, we’ll be able to see some of that flickering of starlight as it’s behind the atmosphere of Pluto.

Fraser: Well, enough about our boring solar system. There is some crazy weather out in the universe. I mean, you think of some of the extra-solar planets that have been discovered, you know, let’s hit some of the highlights because there’s some really neat planets out there.

Pamela: Well, I think the highlights are all with the planets that are sufficiently close to their parent star that they’re tidally locked, so you have this whole family of planets that one side of the planet and only one side of the planet always faces the Sun, just like our own moon only shows us the “Old Man in the Moon,” and never lets us see the pockmarked other side of the Moon. Now, if you only have one side of your planet ever facing the Sun, that one side is going to get pretty, pretty hot and that sets up massive convective zones that instead of being bands that run parallel to the equator, you instead get convective zones that have cells that are passing the air from the sun-facing to the non sun-facing side of the planet, and we have models that are trying to understand what’s going on, but this is something we’ve never seen before outside of our computer simulations.

Fraser: Yeah, it was actually surprising…I know that when these planets were discovered it was surprising how well they actually did move the heat from the face that, you know, the one that’s facing the star to the other side. They actually found that the global temperature differences weren’t as extreme as they thought, so you can just imagine there must be some ferocious winds, like, what, faster than 1000 km/hour — just incredible winds blowing from one side of the planet to the other side to circulate this heat around. Just amazing!

Pamela: And one of the things about, at least I think, one, maybe more of these planets (you always have to say “maybe more” because they’re finding new planets every time you blink), but one of these suckers is within the region of its solar system where liquid water can exist on the surface of the planet. So you have this planet orbiting a red dwarf star so close that it’s tidally locked, but were it able to behave like a happy, normal rotating planet, it might have had oceans, but now it instead has insane weather instead.

Fraser: And this is going to be one of these things, you know, the more of these planets that we find, the more of these crazy extremes. I just wish that we could see them closer, better, but we just can’t.

Pamela: Yeah, it’s one of those frustrating things, but what’s kind of cool, though, is at least if they are polite enough to transit in front of their star, we can get a measure on what’s in their atmosphere, so that’s at least something.

Fraser: That’s pretty amazing when you think about it. Alright, well, that’s great, Pamela. Thank you very much. Now we know “why is the weather,” and I’m going to go out and enjoy it.

Pamela: That sounds great. I hope you’re having a slightly warmer day today.

Fraser: Yeah, it’s a total, horrible spring, but I’ll do the best I can. OK, we’ll talk to you later Pamela.

Pamela: OK, bye-bye.

Show Notes

This transcript is not an exact match to the audio file. It has been edited for clarity.

Transcript: The Transit of Venus

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Fraser: Welcome to Astronomy Cast, our weekly facts-based journey through the Cosmos where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain, I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University at Edwardsville. Hi Pamela, how are you doing?

Pamela: I’m doing well, Fraser. How are you doing?

Fraser: I’m doing really well. So since the planet Venus is closer in to the Sun than Earth, there are rare opportunities to see it pass directly in front of our parent star. This is known as a planetary transit, and thanks to the geometry of the Earth and Venus, they only happen a couple of times a century. The transits of Venus have been used by astronomers to unlock the scale of the solar system, and there’s one just around the corner. Alright, Pamela, so today we’re going to talk about the transits of Venus. So first I think, when we think about the geometry of the Solar System, it almost seems obvious, right? The Earth is farther away from the Sun than Venus, and so as Venus orbits more quickly than Earth, you would kind of imagine Venus passing right in front of the Sun like several times a year, or once a year anyway, so why doesn’t that happen?

Pamela: Well, the reality is that the orbit of Venus is shifted 3.4 degrees relative to the Earth, so this means that if you had two hula hoops, one smaller than the other, and you lined them up just like Earth and Venus, the one on the inside would be tilted over 3.4 degrees, and the distance between Venus and the Sun is so great that that small shift means that most of the time, we see Venus as appearing above or below the Sun in the sky, and this difference prevents transits from happening on a regular basis.

Fraser: Right, so when we are able to see Venus, it’s not lost in the glare of the Sun, then we’re sort of making a direct line from us to Venus to some point on the background sky, you know, it’s not passing in front of the Sun, but even when Venus is lost in the glare of the Sun, it’s actually a little above or a little below the Sun, right?

Pamela: That’s exactly the problem we’re dealing with and the only time we ever see a Venus transit is that magical moment when it just happens to be that the Earth, Venus and Sun are lined up just as Venus is at that mid-way point in its orbit, at the node in its orbit, where it crosses from above the Sun to below the Sun, and that doesn’t happen very often.

Fraser: Right, I can imagine it, right? It’s almost like it’s…sometimes it’s above the Sun, sometimes it’s below the Sun…it’s just when everything lines up. So how often does this happen?

Pamela: Well, it happens in a pattern of…you’ll get a 105.5-year gap, an 8-year gap, a 121.5-year gap, and an 8-year gap, and this keeps basically repeating over and over and over due to the patterns of how the Earth and Venus orbit against one another. There’s a basic resonance in the system, and so it’s nice we happen to live when we can see a pair of these 8 conveniently for our adult lives, but there’s a whole lot of people that are going to live and die in those 100+ year gaps that will never have the opportunity to see this, but right now there are some people that got to see the 2004 transit, and there will be others who will get to see the one in 2012.

Fraser: But that’s kind of strange. I mean, you get an 8-year gap, so that’s like what we’re about to experience. We had one in 2004, and then we’re going to see one in 2012, and then you get…what was it? A one-hundred…

Pamela: You have 105.5 and 121.5-year gaps

Fraser: 105 and 121, so why do you get a short gap and then a long gap?

Pamela: It’s just the way things happen to line up where you’ll get two hits, so you can sort of imagine if you’re watching windshields beat up against each other where you’ll get two back and forth strokes if they aren’t quite perfectly in alignment, where it looks like they’re aligned and then they’ll go out of cycle for a long time, and then you’ll come back and you’ll see two that appear to be in line together, and it’s just this partnering of those two sets, you end up with it just briefly allows these two alignments to come together perfectly.

Fraser: We often get solar and lunar eclipses paired up in kind of the same way.

Pamela: This is the exact same sort of process.

Fraser: Right, it’s because the planet and the Moon and the Sun are all nicely lined up on the one side of the Moon’s orbit – you get the solar eclipse, and then 15 days later or less, you get the lunar eclipse. It’s just because they’re all still kind of lined up. I guess that’s what Venus…it’s like you’re getting one side of it being lined up, but it’s still kind of aligned, but the next time it goes past the Sun from our point of view and so you get that alignment, and then it’s completely out of whack for the next 100 years.

Pamela: Right. So this is a rare event and it’s kind of fascinating to look back over history and think that in the amount of time that we’ve actually understood orbits, this has only happened really on seven times, and it’s only been observed five times, or at least observed well.

Fraser: Mmhmm, and one in our recent history… So then let’s kind of go back then — when was this concept even understood? Right? I mean, did astronomers know that these transits were happening, and they just couldn’t observe them, or when did somebody say, “Hey I’ll bet Venus is passing in front of the Sun?”

Pamela: As near as we can tell, in ancient and medieval history no one noticed this. Now they didn’t exactly have pinhole cameras for projecting the Sun up on walls; they didn’t have lenses, so there’s no real way to observe this happening, and in fact, it wasn’t until Pythagoras came along that people recognized that Venus in the morning and Venus in the evening were even the exact same object. So it really took until Kepler came along in 1627 and started running numbers that we’re able to make this sort of prediction. And unfortunately, while Kepler was working, while he was working with the most precise numbers at the time, we still have a lot to learn. And so when he predicted the 1631 transit, he wasn’t able to predict where on the planet it would be viewable from, so it wasn’t viewable in Europe, and no one actually made arrangements to go see it where it would be visible because, well, we were still sort of figuring that sort of thing out.

Fraser: Hold on, so it actually depends on where you are on Earth on what you’re going to see?

Pamela: Well, it’s the old problem of half the planet’s looking toward the Sun and half the planet’s looking away from the Sun, and you have to be on the part of the planet that’s looking toward the Sun and be able to see Venus and the Sun in the sky at the same time, which is anyone who could see the Sun, in order to see the transit.

Fraser: So the transit has to occur during your “day?”

Pamela: Right, and if it’s nighttime during the transit, you get to sit on your thumbs and be bored.

Fraser: Right, or get traveling, and I guess back in the day, that was a pretty serious commitment. I mean, if you’re in Europe and you’re not going to see it unless you’re in North America or in Asia, that’s a big trip.

Pamela: Those are major endeavors and this actually led to a few people having a lot of life difficulties, I guess is the best way to put it.

Fraser: I know, there’s some amazing adventures in trying to see this transit.

Pamela: There was this poor fellow by the name of Guillaume Le Gentil (and this is where I say I can’t say anything in French correctly), and this poor fellow took off to try, try to view the 1761 transit, except it…pretty much the planet was against him. There was French and British wars to contend with, Spanish uprisings in various places…this was during the Colonial Period, and the poor fellow was basically trying to get originally to a French colony in India and finally arrives after all sorts of trials and tribulations, bouncing all over the planet in some regards — and he gets clouded out.

Fraser: [laughing] That was like you seeing the solar eclipse and you got clouded out.

Pamela: Except for me I had the option to just hop on a plane and fly home and I was home two days later. So this poor man, he’s gone all the way around the planet, and he decides that he’ll just stick around for eight years, and — I mean, can you imagine? This is a married man, who in the name of science, decided to just spend an extra eight years.

Fraser: Yeah, that would really fly in my house.

Pamela: Yeah, I think I’d be a dead woman. There are no number of spousal permission units for that one. So he decided to spend eight years mapping the eastern coast of Madagascar, which was a good use of his time, and he continued doing various astronomical observations, but then come June 4, 1769, according to what I’ve been able to read, he’d been dealing with beautiful glorious awesome weather, day after day after day after day — until the day of the transit, and he pretty much went insane at this point, and it took him a while before he reached the point of being able to pull himself together and consider journeying back to France. By the time he finally got home in 1771, his wife is remarried, his family plundered his estate (they’d assumed him dead), he’d lost his academic posting, and the King of France had to intercede to get this poor man’s life back together.

Fraser: Well, sometimes you gotta take those big risks for science.

Pamela: You know, I’m willing to pull the all-nighter occasionally, but 11 years facing things like dysentery and civil war is not something I’m willing to do in the name of astronomy.

Fraser: You just don’t want it bad enough then.

Pamela: No, I don’t. I don’t.

Fraser: OK, so that’s just one – I know there’s a whole pile of stories, but I think even further back astronomers started to get a sense that the transit of Venus was something that they needed to observe.

Pamela: Exactly.

Fraser: But why?

Pamela: It’s a simple reason: we didn’t know where the Sun was. We knew it was in the sky. We knew that it was a standard distance away from us because it didn’t appear to change in angular size all that much. We knew there was some variation, but since we didn’t know the exact size of the Sun, we couldn’t say how far away it was precisely, and the hope was that if you got two different people observing when Venus appeared to cut in front of the Sun, and when it appeared to come back out again, that by timing these transits, and being on different north-south lines, we’d be able to calculate via parallax the distance to the Sun — and it worked!

Fraser: Right. So just to understand this: I’ve got it’s not about making one observation; it’s not like me going to India setting up the telescope and having good, clear skies and being able to make my observation. It’s about me being on one spot on the earth, and you being on another spot on the earth at the same moment, and us both doing our observations, and then the difference between our observations is what then gives us the triangles that we use to calculate everything.

Pamela: Right, and you can get a long way simply by doing one observation and carefully measuring “when does Venus start to pass in front of the Sun?” and we break this up into four different contact points: so there’s the moment at which the leading edge of Venus touches the Sun, there’s the moment at which the trailing edge touches the Sun (so now you have the full disk of Venus in front of the Sun), there’s the moment of which the leading edge of Venus touches the other side of the Sun, and the moment that the trailing edge of Venus touches the other end of the Sun as Venus completely leaves being in front of the Sun. And we know how fast Venus is orbiting, and that gets us part way there, so you do want multiple measurements; you do want multiple measurements from multiple places, but it’s a matter of: you need all four timings as well to get you there.

Fraser: Right. And so the more measurements you get, the more people who measure all those different timings, then you can build that accurate thing. So you’ve got all these measurements, the astronomers come back together, they do some math and then what does that tell them?

Pamela: Well, for the 1761 and 1769 pair of transits, Jerome Lalande was able to calculate that he thought that the Astronomical Unit — the distance to the Sun — was a 153 million km. This was only good within a million kilometers, and it turns out that it actually wasn’t good within a million kilometers, but this was the most accurate number we had up until that point of how far away the Sun was, so that was an excellent start. And then the next set of transits in 1874 and 1882 allowed us to get to the point that it was within a million km accuracy, so they came up with 149.59 million km, and the real number is 149.598 and then we can add more digits. We actually know the distance within meters, but that number changes depending on where we are in our orbit.

Fraser: But before that, literally, astronomers had no idea. Like it’s probably not 20 km away, but it might be 10,000, you know? We’re not really sure, so you know, it might be 100 km away, in fact, as you said, it’s 150 million-ish km.

Pamela: We knew it was beyond the moon…

Fraser: Yeah, I know, and they just had no sense of scale at all, and suddenly they now were within degree bars that were quite comfortable to wrap your head around.

Pamela: And from Kepler’s laws, by knowing the distance from the Sun to the earth, we could then scale the entire solar system because we knew how the ratios of the planets worked. We knew that if the Earth orbits at this period of time, and Venus orbits in this period of time, what the ratios of their distances from the Sun had to be, and so this one simple, but hard-to-get-physically-to measurement allowed us to not just measure the distance from the Earth to the Sun, but effectively measure the distance from the Earth to everything else that we’d observed orbiting the Sun.

Fraser: Yeah, it unlocked our place in the universe, as we understood it then, you know, and then later on you get the other sort of deeper understanding about the rest of the scale the distance to the stars the other galaxies, but for a while there just knowing the size of the solar system — I’m sure was pretty amazing.

Pamela: It was a step in ever growing our solar system.

Fraser: Now, I know there are more hilarious, hijink anecdotes for people trying to see these transits. Are there any more great stories?

Pamela: That’s really the one that is so amazingly over the top that everyone repeats it over and over and over. There is, of course, Captain Cook made observations at a point that is still called Venus Point, Catherine the Great invited people to observe the Transit in St. Petersburg…so I mean, can you imagine a royal party just to watch and astronomical event? That’s just a fabulous idea. We need more kings, queens, presidents and prime ministers inviting people to make astronomical observations, but those were the main ones. The big issue is for a long time you pretty much had to get to awkward locations like random archipelagos to make good observations, and in days where ships were powered by the wind, that wasn’t a good thing to have to experience.

Fraser: Yeah, yeah, I mean, I guess if you knew the next transit was going to come in eight years, you started to go pretty soon, you know, give yourself a year to get over there, right? So then the next one — now there was the one that was in 2004 I didn’t get a chance to see it. Who got to enjoy that one?

Pamela: Europe’s had a very good view and bits and pieces of North America got to see it during sunrise. I and some other colleagues made a foray up to Nova Scotia because that put us an extra hour to the east and we had some very nice telescopes set up overlooking the Bay of Fundy, which is absolutely a fabulous location to be, and we got rained on so we used our telescopes to view baby eagles plunging themselves happily into the Bay of Fundy, but folks in Boston, where I could have stayed home, were able to see it as the Sun came up, [laughing] and there was an excellent view in lots of parts of Europe.

Fraser: But you didn’t stay eight years, though.

Pamela: No, no.

Fraser: You’re not still there right now…so let’s talk about the next one, then. When is it? Set your calendars everybody.

Pamela: Set your calendars. And now is the time to make your reservations because hotels will book up, and tour groups will book up. So the next one is scheduled by the Sun and gravity for June 6, 2012 and it will be visible at sunset for all of continental North America, Mexico and northern South America. Unfortunately for southern and central South America, no transit is going to be visible – it’s nighttime. And the same is true for South Africa and much of the west coast of Africa, but then if you want to see it during sunrise, just travel to the eastern coast of Africa and to anywhere in Europe except for Spain and Portugal. Spain’s kind of “iffy” depending on where you are, but everything to the east of Spain and northward…it’s going to be visible during sunrise all the way to about the midpoint across Russia and China, and then for the rest of the parts of the world that I haven’t mentioned that much about, it’s just going to be visible the entire time, so much of Australia, all of Japan, Indonesia, Alaska…it’s going to be visible in its entirety. And in fact the best place in the world to be is going to be off the coast of Japan – a ways off the coast of Japan, but in the no-man’s-land where nothing really exists.

Fraser: Come on, western Canada? Will we be able to see it in western Canada?

[laughing] You are able to see it if you go north, if you go way north, it will be visible during daylight and the rest of the time it’s going to be…you’ll be able to see it during sunset.

Fraser: Perfect. Barbecue! I’ll have a barbecue.

Pamela: That sounds excellent…perfect summer weather.

Fraser: Perfect summer weather, transit of Venus in the middle of it, sounds good. You’re all invited. People are going to take me up on this…[laughing]. So now don’t just stare at it with your eyeballs — standard, “you’re looking at the Sun” precautions apply here.

Pamela: Yes, in fact the best way to enjoy this is to make yourselves a pinpoint projector. Take a piece of foamboard, poke a hole in it and you can fuss with it, actually I’ve seen a lot of people take these things and attach them to camera tripods, and things like that where you can use the part where you normally stick your camera on the tripod, use that as the flat surface to attach the foamboard to and then move this around until the Sun is shining flat against the board, and then use a second board or a wall or something else to project an image of the Sun onto. Now, if you’re feeling a little bit more industrious, one thing I’ve found is a great way to view these things is Edmund Scientific sells these tomato-shaped telescopes. There’s really no other way to describe them. They are these little, red — maybe you’ll see them looking as like some sort of a crazy beaker — they’re strange-shaped bright red, cherry tomato telescopes.

Fraser: Like a gourd…

Pamela: Yeah, basically, and they’re not that expensive, and they’re very hard to destroy. And what you can do is just pull the eyepiece out, point the telescope at the Sun, and project the light that is coming out through the eyepiece onto a wall, and this is a really good way to get a nice, crisp magnified view of them.

Fraser: See now, I think that’s cool, you know, but taking something that people are only going to see, for many people never in their lifetime, and using a piece of cardboard to watch it…like what would be the greatest experience? You know…

Pamela: OK, so the absolute best way to observe this, if you’re willing to invest some money, is to get a nice set of neutral density solar filters. These are filters that allow you to continue to see sunspots. They don’t let you see the corona and they don’t let you see the granulation on the surface of the Sun, but those things can really confuse you if you’re trying to watch Venus transit. So just a nice Baader Sun filter for a good 4-inch telescope is really all you need.

Fraser: What about binoculars?

Pamela: You know, I actually bought solar filters for my binoculars, so I just have a pair of everyday Nikons. Now, the problem that I’ve run into (and this may be one of I’m not a coordinated individual) is when you’re trying to point binoculars at the Sun, you either see absolutely nothing, or the Sun. So, it’s not like you can go “OK, the Sun is straight up from that lamppost. Find the lamppost; scroll up on the sky.” No, you just have to sort of dead reckon your way to the Sun.

Fraser: I think people can work their way through that problem.

Pamela: [laughing] OK.

Fraser: Yeah, so again though, it’s almost like the kind of binoculars you’d want for doing some really nice stargazing, or even planetary observing are total overkill for this kind of a job.

Pamela: Actually, it depends on how active the Sun is. The thing about the 2012 one is there is some potential for there to be good sunspots, so having reasonably good binoculars where the Sun nicely fills your field view and allows you to see sunspots, I think, is completely reasonable. The real trick is just getting a good fit on your solar filters because they come in a lot of different sizes, they’re not necessarily brand-specific, and the trick I actually learned…I bought a nice pair of filters from Oceanside Photo and Telescope that found filters that, in theory, matched my binoculars, but I didn’t trust the filters to actually stay on is I got foamy tape, that type of tape that you might put on the bottom of a television or something to make sure it doesn’t scuff shelves, and I just put foamy tape all around the inside of the filter cap, and that made a much snugger fit.

Fraser: And so how long does the whole transit take?

Pamela: Hours.

Fraser: Oh, really. OK.

Pamela: Yeah, this is an all-day…you’re idea for a barbecue is actually pretty much right. You can start heating up the charcoal at first contact, and be finishing off your ice cream and thoroughly exhausted and children melting in the corner about the time that it’s ending.

Fraser: Right. Right. OK.

Pamela: With time for a game of volleyball in the middle…

Fraser: And one thing that’s kind of neat to add on top of that is that if you’re going to test out a pair of binoculars or your telescope to see if you’ve got the right kind of magnification, you can always use the moon as a stand-in because it’s the same size.

Pamela: Right, so before you even buy one filter, just go out and look at the moon.

Fraser: Yeah, and that will make sure that you’re happy with the size. And then how big will Venus appear?

Pamela: [laughing] You know, the last transit there are a few pictures…I’m actually thinking of the last Mercury transit, not the last Venus transit…there are pictures where some of the sunspots were bigger than Mercury was and bigger than Venus would have been. So if you think of a nice, really large sunspot cluster, that’s about how big Venus will appear, except Venus is a nice, perfectly crisp, round object as it passes in front.

Fraser: Right. But we won’t see like a shadow?

Pamela: No, no, no…

Fraser: Since the Sun is the thing that’s putting out the light…OK. Well that’s great, Pamela. I’m really looking forward to watching the transit. This time I get to see it, so that’s fantastic! Well, we’ll talk to you next week. Thanks!

Pamela: Sounds good, I’ll talk to you later.

Transcript: Mass Extinction Events

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Fraser: Welcome to Astronomy Cast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain, I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela, how are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: I’m doing really well, let’s roll. Happy Valentines Day!

Pamela: [laughing] For those of us…for those of you confused (we’re already confused) for those of you confused by the laughter…

Fraser: …we recorded this about six weeks late.

Pamela: Right, so we record things in order. We backdate things so that in the future, the weeks that we release 4 and the weeks that we release 0 even out to one a week.

Fraser: This is going to be one of those “4-in-a-week,” so lucky you! Alright, so the Earth seems like a safe place most of the time. With evidence of terrible catastrophes in the ancient past, times when almost all life on Earth was wiped out in a geologic instant, what could cause so much devastation? And will something like this happen again? So, there are a few of these names, right? There are these various extinction events and they all — many of them — have names.

Pamela: K-T extinction is the one everyone talks about.

Fraser: The K-T extinction, yeah, yeah, the Permian Extinction, the…
?

Pamela: Late Devonian — that’s just fun to say!

Fraser: Yeah, so there are all these big extinction events, and in each one of these, everybody died.

Pamela: Or at least most stuff…

Fraser: Most stuff died all at the same time, right? So, when scientists define a mass extinction event, what are they talking about?

Pamela: For the major ones, there’s usually something where 50% of the varieties died off, so for the — just to grab one — the Triassic-Jurassic extinction event; this was about 205 million years ago. This one about 40% of all genre, if you remember that big “tree of life” you had to learn probably in high school, 48% just died on land.

Fraser: Right, and this is the way they measure them, right? They look at the fossil record before the moment — the event — and count up the variety of species in the rock layer, and then they take a look after the event and count up the variety of species, and you’re looking at, there’s 50% variety, but it’s not necessarily how many creatures died, it’s the…how different are the creatures that are remaining.

Pamela: And it also goes into things like: Was it only on land? Was it only in the ocean? Did everything everywhere die? And what’s interesting is, like, bugs have a tendency to live.

Fraser: Cockroaches, yeah…

Pamela: They will out-survive all of us, and so you start looking at the different places that things died, and you also start looking at the varieties that died: Did you only lose the dinosaurs? Did you only lose the frogs? Which currently we’re undergoing a massive extinction event. We’re in the midst of what may be the number six (or it may be even higher than that) extinction rate that the planet Earth has ever had, so we see frogs going away, amphibians in general going away; we see bees going away, birds going away, so as we start losing biodiversity across the planet, that is the definition of an extinction. There’s still life everywhere, but the types of life are decreasing in radical numbers.

Fraser: But it’s hard, you know? The extinction event that we’re in right now — it’s hard to notice it. It’s not like I notice like, “Oh, there’s one less type of frog showing up in my backyard these days,” but I don’t think that the previous extinction events happened that subtly, right?

Pamela: Well, so when the dinosaurs died — giant asteroid fell out of the sky — that was rather noticeable [laughing], but some of the other extinction events, we’re not sure. They could have been like the one we’re experiencing right now, could have been the type of great dying that it took time, and it was due to an environmental change, and so while you did have massive amounts of death and destruction of life forms, it wasn’t a sudden “in the moment” destruction, and we’re in one of those “not in the moment” destructions right now.

Fraser: So then, can you give me some examples of some of the big ones? What were the big extinction events?

Pamela: Well, the most recent big extinction event was…

Fraser: Yeah, we’ll go backwards.

Pamela: OK, so the most recent one was the Cretaceous-Tertiary Event, which is spelled with a C and a T, but is referred to as the K-T Boundary, which is one of those things that just baffles me, so there must be a language where Cretaceous is spelled with a “k” and that would just make me happy.

Fraser: Russian or something…

Pamela: They don’t so much have the “c” and the “k,” but I’m right there with you.

Fraser: Right, and that’s 65 million years ago, right? That’s the famous one that killed the dinosaurs.

Pamela: And here we’re looking at, we’re trying to figure out the geological boundary between “have dinosaurs”/”don’t have dinosaurs” – it’s an important boundary. Below here lie the T-Rex…when we start looking at this boundary, it was actually discovered that there’s a very distinct difference in the geology of that boundary layer. This is research that was done by Lewis Alvarez and his son Walter Alvarez, as well as the chemists Frank Asaro and Helen Lanko (editor’s note: chemist’s name is Helen Michel), and what they found is there’s iridium, which is extremely rare on Earth, but is rich in certain types of asteroids. There’s basically a planet-wide layer of iridium at the dinosaur/no dinosaur boundary.

Fraser: And it’s also like a dark black line, isn’t it? I’ve seen them sort of showing you the K-T Boundary… it’s this black line that runs in the strata.

Pamela: And so you can actually see something happened, and it’s believed that this was caused by some sort of giant impact here on the planet Earth and this, of course, is where you start trying to figure out “OK, where’s the big hole in the ground?” And living on a planet that’s largely water, it can be a bit annoying at times, but this one actually is partially on land. And it looks like the Chichalu coast of the Yucatan in Mexico is part of an impact crater. And it was partially oil geologists — people out there surveying to figure out where to find petroleum resources are in part responsible for finding this crater because as they were going out making measurements of “OK, I know how far I am from the center of the planet Earth, what is the gravitational pull where I am right now?” And by combining the information of where you are and distance with the amount of gravitational pull you experience, you actually get a sense of the density beneath you, and they found these gravitational anomalies that added up to: there’s an area of the ground that’s been compacted, and this is that crater.

Fraser: And so then, you know, looking back in time, what do they think happened? You know, it’s a big space rock, but as a good example for the kind of event, what are we looking at happened?

Pamela: So basically, you have rock from the sky comes in for a rather violent landing, and based on this 180-or-so km crater, you can guess that when it impacted, there was a lot of rock that was basically turned into dust and thrown into the upper levels of the atmosphere. There’s a fabulous scientific American caption that says when it hit it threw dirt, rock and dinosaurs out of the Earth’s atmosphere — and that potentially happened! So you can just imagine being the poor dinosaur munching leaves or munching another dinosaur, and you look up and there’s giant rock coming from the sky, burning up, huge light, fire, ground shakes…and the shock wave goes traveling through the ground and it’s that shock wave that’s so dangerous and throws things up, and that shock wave leads to you being thrown into low Earth orbit and dead.

Fraser: Yeah, but what about the rain of molten rock that falls down around the whole Earth and lights everything on fire?

Pamela: Right, so it’s unclear exactly how much of that story would actually have happened, but there is a problem with molten rock being generated and tossed up, and then it’s a matter of: How long is it in the air? Does it have a chance to cool off? Does it actually have ignition temperature when it hits the ground? None the less, there’s all this stuff thrown into the atmosphere; this leads to acid rain which kills vegetation, kills plankton, kills all the stuff that gets eaten by the things further down on the food chain. Those things start dying, so things at the top of the food chain start dying. You have changes in the planetary temperature, which makes cold-blooded animals have kind of a rough day. You have all of these things coming together at once, and some things ran for the right environment. Like we now see some animals living further north than they used to trying to find some place where it’s still cool enough to survive. Here you would have had animals and things running toward the equator trying to find someplace warm enough to survive.

Fraser: Right, so you would have had the event itself, and, you know, exactly how devastating that was is unclear, but in the worst case scenario, it’s like the whole earth was on fire with temperatures hot enough to boil water everywhere you went.

Pamela: Right.

Fraser: Right? And the only place you could survive is if you were quite a depth underground, and even when you emerged the entire planet was cooked to a crisp, nothing to eat…Not a good day, right? Not a good day to go hunting for food…

Pamela: Yeah, it probably wasn’t that extreme. There is evidence that things did live for a while, and it was that “Wow!”…

Fraser: Right, and so afterwards, right? You get this horrible event in the moment, where it’s possible there’s nowhere safe on Earth at all, and then you have the after-effects, where it’s also a very horrible place to live for a very long time. You’re looking at, what, hundreds of years before things might get back to normal?

Pamela: And this is where it’s unclear, but you’re definitely looking at 10s of 1000s of years for the diversity of life to recover, and so we’re unsure exactly how long it took for the suffering to end, basically, so there was still a couple tens of thousands of years where it looks like some dinosaurs managed to just barely hang on, but it’s unclear how much of that is …you can actually have fossils move around in the geologic record, which is kind of annoying, so for plus or minus a few 10s of 1000s of years there’s a question mark, but it looks like you could have had a few tens of 1000s of years of things barely making it before they just died off and were replaced by new, up-and-coming life forms. So all non-avian dinosaurs died off near this period. Some of the avian ones, well, they still exist today — we call them birds.

Fraser: Right, so we’ve got all of the birds surviving and some of the mammals and some of the plants, and then…and insects, and then you get this re-speciation, right? So shortly after you’ve got very few species, and then things recover.

Pamela: And what was amazing about the K-T Boundary is it pretty much killed everything off that was big and wasn’t cold-blooded, and the reason this is: you can take a cold-blooded animal and get it cold and it basically hibernates and stops eating, so things like crocodiles could survive, but all of the big dinosaurs that were a wee bit warm-blooded in one way or another – dead. Any large mammals that might have existed – dead, but luckily, most of the things were small at that point, and the small mammals, the avian dinosaurs (which in order to fly you have to have fewer demands on your system where you get too massive and flying becomes hard), all of these things were able to survive this period. The other thing that’s kind of weird, though, is pretty much all of the northern marsupials died off. You don’t really think of marsupials in dinosaur times, but there were a bunch of marsupials in North America and some in Asia, and they were all gone after this boundary period, so that’s just one of those weird, “Huh!” things that came out of this extinction.

Fraser: We could have kangaroos here in North America if things had gone differently.

Pamela: That would be so cool!

Fraser: Right, so the K-T is the big, famous one, but there are some other ones that make the K-T event look kind of small in comparison.

Pamela: No, that would be entirely true.

Fraser: Yeah, so like your worst day ever is nothing compared to the Earth’s worst days ever.

Pamela: [laughing] Yes.

Fraser: The dinosaurs’ worst day ever…so let’s talk about some other mass extinction events and how they’re different.

Pamela: So, we’re going back in time. The next big “bad boy” of the extinctions was the Triassic-Jurassic extinction event, and this was one where you lost vast amounts of the stuff in the ocean, and so that’s one of the things that makes you notice: what caused the ocean of all things to have problems during this period? A lot of the large amphibians were able to survive, but the aquatic environments just had these huge die-offs – 20% of marine families, 55% of marine genre became extinct — and so in trying to figure this one out, there aren’t any asteroid impacts that seem tied to it, and well, it looks like there were gradual sea-level fluctuations. It doesn’t explain the suddenness of what happened in the marine environment, and so it’s thought maybe this was due to some sort of volcanic eruptions, and there’s what’s called the Central Atlantic Magmatic Province, which is basically this large expanse of magma that was created, and any time you have lava coming out, if you watched any of the eruptions recently in Japan or Indonesia or Iceland or Hawaii, you end up with carbon dioxide, sulfur dioxide and all this stuff just thrown into the air. And if you have basically continent-wide magma release, that’s going to throw vast quantities of stuff into the atmosphere and cause some sort of a temperature effect globally, and with the combination of changing ocean levels predicted, and this predicted change in the environment – all of these factors together probably led to just reaching a point where life just wasn’t sustainable anymore, and you had massive die-offs.

Fraser: But it’s interesting that it was largely targeted in the water, as opposed to on land as well, I mean, I wonder if huge eruptions under water or something just started off.

Pamela: Well, there’s that, and the other thing is if you have changing ocean levels, if you look at where the most diversity of life is, you’re looking at the low-depth areas, the coral reefs, the edges of the crustal plates, basically, and it’s in this slope down to the deep sea trenches that you have so much life and if you drop the water levels, this long expanse of shallow water goes away and all those places for biodiversity go away.

Fraser: OK, so let’s keep moving back.

Pamela: So, the next big one we have is the Permian-Triassic, and this is where you start thinking about “where did oil come from?” Well, that’s Permian times, Triassic times, and so when we look back at this: this is the Big Death. This is 96% of all marine species, 70% of terrestrial vertebrates – everything died…dead, dead.

Fraser: This is the Great Dying, right? If you hear anyone talking about the Great Dying, this is the event.

Pamela: No more life.

Fraser: No more life.

Pamela: None.

Fraser: None. Wow! Well, obviously some because here we are.

Pamela: [laughing] Right, so there were those remaining 30% of terrestrial vertebrates, remaining 4% of marine species… The weird thing about this is: this is the death that killed insects. There’s really no other “dying off” that killed insects. And the other thing about this is there’s actually a gap in coal being created during this period, so if you’re looking for coal to come from during the Permian-Triassic extinction event, there’s no coal there.

Fraser: And there are whole – I’m not a biologist, so I forget the classification – but there are some basic types of animals, really basic body plans, and they disappeared during that extinction. I mean, you have whole branches of the “tree of life” that went away.

Pamela: 96% of corals, for instance, went away.

Fraser: Yeah, I know, I know, but you have like whole types of animals (I’m sorry, biologists, but you know what I’m getting at, right?) that went away.

Pamela: Trilobites – gone! The coolest fossil ever – all gone!

Fraser: And so there are whole kinds of life that just never made it past that moment, that event.

Pamela: Sea scorpions! Who doesn’t want to have underwater, deadly sea scorpions? But we don’t because of this extinction event. And what starts getting frustrating is we look at these things that are further and further back in time is our planet has this nasty habit or resurfacing its surface, and so as we try and understand what happened in the more distant past, we start to lose the ability to look for evidence of impacts. The crater would have probably gotten worn away, plate-tectonic carried away…so many different things could have destroyed it by now, so while there are impact craters that are linked as possible causes to this, there’s no one thing we can look at and go, “That! That is the cause of this extinction event!” so we look instead at there seems to be a peak in some of the quartz crystals found at the Boundary layer, there’s fullerenes that have trapped all sorts of gasses at the Boundary layer, but that could have just been one local event in Antarctica where all of these things are being found, and in Australia where all these things are being found. That could have just been a regional thing. People also point to all sorts of massive volcanic events that took place. There was massive volcanism going on in China, in the Guadalupe area, in Siberia, and with all of these massive volcanic events, maybe that played a role. Maybe the impact caused the volcanism…we’re just not sure. And then there’s always the case of “Well, why is it that we see sudden changes in the carbon isotopic ratios at this point? Could it be that there was some sort of an out-gassing that caused this change?” So as we look at what could have happened at all of these different things, we’re just not sure, and this particular “everything died” event probably was tied to a whole bunch of bad stuff all happening at once, all feeding off of one another, and what we’re learning is: global catastrophes – one of them can trigger many other things to happen. It used to be thought that if you hit a planet with an asteroid, you caused localized volcanism, well now we’re finding maybe/maybe not. Maybe on the other side of the planet, on the antipode, maybe you had volcanism.

Fraser: OK, so the Earth would be hit by an asteroid so hard that you would get ripples of force moving through the planet, and then bunching up on the opposite side of the planet, and then it would explode as volcanism.

Pamela: Or maybe it’s just enough to take existing volcanoes that were sitting there kind of quiet, kind of minding their own business, and all of them go off at once.

Fraser: And so that seems to be the model right now, like it took a very special circumstance to cause so much destruction. You had to hit the Earth and then when it was trying to get up, hit it again and again and something is [missing audio]…and it’s funny because there’s the “volcano people” and there’s the “asteroid people,” and a lot of people are just like completely on the fence, or “I think it was some of one and some of the other.”

Pamela: I’m right there with you.

Fraser: A little of both makes it seem more likely. What a catastrophe! We’ve done a few articles in Universe Today like that. There is some subtle evidence, as you said, like common characteristics of craters or minerals found around the earth that maybe could have caused that, but still, there’s just no smoking gun, we just don’t know. But if you go further back, there are more of these, right?

Pamela: So we have two more and we’re leaving out all the little punctuated things.

Fraser: Well, that only killed 10%, 20…who cares?

Right, [laughing] so this is where we start getting the Late-Devonian extinction period, well just the Devonian extinction in general. This was an event where, basically, 50% of the genera went extinct all at once. There were probably different periods of extinction during this, and so you saw one die-off, and then not too long after it another die-off. Now, this is one of those that when we start talking about what died, well, the planet didn’t have anything on land more sophisticated than bugs, so it’s kind of hard to measure die-offs when you don’t have giant skeletons to go searching for, so trying to make sense of this particular extinction has taken time where they’ve done neat things like look at fossilized leaves to look at how much insect munching had occurred to try to get a sense of the biodiversity based on what bugs ate. And it’s cool, and this is how we learned lots of things died, and there were two sharp peaks in this particular event of things dying off.

Fraser: You said there was…were those the two events? Is that what you’re saying, there were two events previous? Or was there another one?

Pamela: It looks like during the late Devonian period of extinction there were two separate extinction events. These are referred to as the Kielwasser and the Hangenberg events, and exactly what triggered them we’re still trying to figure out. The Kielwasser one is detected based on marine invertebrates getting killed off, and the Hangenberg one – it’s this final spike of dead stuff that’s basically found in the rock layer, where as you’re looking at the sandstone and the shale layers, you see this material that’s anoxic – it’s just different life that suffered and died, and it’s that marking in the records that distinguishes these two different events that occurred fairly close to one another and killed lots of stuff.

Fraser: Now, the obvious question of course, is will there be more mass extinction events in the future?

Pamela: Yes. Yes, and I…we can go even back further than this. There’s still the Ordovian-Silurian extinction event, and that only affected oceans because there was really only life in the oceans. And whenever there’s been life there’s been death, and sometimes the death clusters up. We’re undergoing massive extinction right now. It’s unclear how much of it is due to global warming, how much of it is due to human beings… I highly recommend reading Guns, Germs and Steel…and there are asteroids in our future. There are potentially supernovae in our future. The Ordovian-Silurian one actually — it’s considered that this might have been a gamma ray burst, this might have been a supernova that affected the ability of our ozone to protect the planet Earth from UV. That could happen to us again.

Fraser: And then, of course, we’re going to have the final one when the sun heats up to the point that it bakes the Earth.

Pamela: I think that one goes beyond “extinction event” to “planet destruction.”

Fraser: Yeah, the final…the “big one.”

Pamela: [laughing] But in the interim, what we find is life has ways of recovering, and while we’ve been undergoing this every few tens of millions of years, extinction’s pretty much like clockwork in a lot of ways, although there’s no extra star, there’s no passing through the galactic plane, it’s just, statistically, we tend to die off every few tens of millions of years. This will keep happening. The universe will keep finding ways to kill us. We have a poster you can buy here at astrogear.org.

Fraser: Yeah, “the Universe is trying to kill us all…” Well, that’s great Pamela, great! Scary, but great! Alright, we’ll talk to you next week.

Pamela: Sounds great! I’ll talk to you later.

Show Notes

• USA Science and Engineering Festival
• Zooniverse
• Europa — Nine Planets
• Simon Marius (1572-1624) — The Galileo Project
• Fubar — Urban Dictionary
• Ice and Water on Europa — Goddard Space Flight Center
• Europa’s Hidden Ice Chemistry — NASA
• Animation of orbital resonance of the Galilean Moons — Wiki
• Paper:  Insights into Europa’s Resurfacing; Figueredo & Greeley
• Voyager Images of Europa (as well as Jupiter and other Moons) — Planetary Society
• Europa Capable of Supporting Life, Scientist Says — Universe Today
• A Submarine for Europa – Universe Today
• Europa-Jupiter System Mission website
• Juno Mission website

Transcript: Europa

Download the transcript

Fraser: Astronomy Cast Episode 203 for Monday October 18, 2010, Europa. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain, I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville. Hi, Pamela, how are you doing?

Pamela: I’m doing well. It’s fall… leaves are falling off… How are things there?

Fraser: It’s good, it’s good. No leaves falling yet… but we’ve got a big piece of news. We’re going to be in Washington in just a couple of weeks.

Pamela: Yes, we’re part of the US Science and Engineering Festival, and we’re going to be performing at 4:00 on Saturday October 23 and come find us… say hello. We’ll also be, all weekend except when we’re on the main stage or otherwise getting a drink or something, in general, we’re going to be at the Galaxy Zoo booth the entire time and your program will have a map of how to find Zooniverse, Galaxy Zoo, Moon Zoo, and all the citizen science goodness.

Fraser: Yeah, we’re going to do an hour show on why Pluto isn’t a planet. The rest of the time we’ll be around to hang out and talk science.

Pamela: So come say “hi!”

Fraser: Ok, on to the show. Europa is the smallest of the Jovian satellites, but it might be one of the most exciting spots in the solar system. When NASA’s Voyager spacecraft flew past the moon, they discovered huge cracks in its icy surface. Is it possible that Europa has a huge ocean of liquid water and maybe even life? This is a world that needs more investigation. Alright, Pamela, I’m going to guess who discovered this Galilean moon?

Pamela: Well, I think maybe it might be this dude called Galileo Galilei, but you know there’s actually a little bit of debate on this one. So even though it’s called a Galilean moon and you’d think that it’s 100% obvious that full discovery credit should go to Galileo, it looks like it might also have been independently discovered by Simon Marius. So this Galilean moon may have been discovered twice and might need a little footnote pointing to Simon, but then there’s also controversy saying he just plagiarized, so…

Fraser: But anybody pointing a 20-power, 30-power telescope at Jupiter would have discovered Europa, I mean, as soon as you have the tool, the discovery is right there. You could make that discovery right now today with a small telescope or even a powerful pair of binoculars.

Pamela: What’s interesting is that as easy as this thing is to see, it occasionally lines up just right so that you don’t see it. So yes, you can go out, you can see it with binoculars, you can see it with the cheapest dime-store telescope you can buy for more than a dime. But Galileo himself discovered it on his second night of observing because on the first night he was observing it, it was merged with a different moon.

Fraser: Oops!

Pamela: Well, yeah.

Fraser: And then where does it stand in orbits compared to the other Galilean moons?

Pamela: Europa is the second out from Jupiter of the Galilean moons. It went by the name Jupiter II for a long time because people didn’t want to use the name Europa.

Fraser: Boring!

Pamela: Yeah, yeah, yeah, I know. We’re astronomers… we crave the boring! So it goes Io… which is grabbing all sorts of energy out of Jupiter… then Europa, Ganymede, and Callisto’s the furthest out of these four giant moons.

Fraser: And before the Voyager spacecraft, what did we know about Europa?

Pamela: That it was shiny.

Fraser: So like icy? Maybe?

Pamela: Well seriously what we knew was it’s shiny, and ice is what we always assume, but this object was reflecting huge amounts of light and being as tiny as it is, you have to pretty much be made of glass, mirror, ice (ice being most likely) in order to reflect as much light as Europa’s able to reflect given its size.

Fraser: And as better instruments came along, and as missions were sent there, yeah… absolutely… it’s ice.

Pamela: And what’s cool is even though its surface is pure ice, unlike several other… particularly of Saturn’s moons that are pretty much all ice, Europa appears to probably have an iron core, to be made mostly of silicates… the type of stuff that terrestrial planets—our own Earth—are made of. It’s only the outer maybe 100-ish kilometers or so that are this liquid ice and solid ice that does all the shininess.

Fraser: Right. Liquid ice… I believe we call that water.

Pamela: That’s true… yes, that would be true. Ok, we’re just going to leave that fubar into the show… you can all enjoy it.

Fraser: Ok.. alright. Let’s talk a bit about the orbital mechanics because Europa, I know, has a relationship with the other Galilean moons.

Pamela: Right. So, there are these orbital resonances which cause the planets to go around and keep repeatedly lining up with one another. So for every one time that Ganymede goes around, Europa goes around twice, and Io goes around four times. And this beating of the moons against one another causes, first of all, their orbits never completely straighten out to being 100% circular. That’s just not going to happen with this repeated lining up. The other thing that it does is it causes… the combination of Jupiter’s gravity and this constant tug-of-war gravitationally with the other moons flexes each of these moons in their own horrible way. Io suffers the greatest where we have this rocky world turned molten. But Europa, with its slightly, slightly eccentric orbit goes from when it’s closest to Jupiter getting squished a little bit, and then when it’s furthest from Jupiter getting to relax. This squishing and relaxing and squishing and relaxing actually builds up heat inside this little icy moon. That heat is just enough to probably keep a good thick layer of water on top of the silica and metallic core of the moon.

Fraser: Right. If we had a whole pile of water on top of Io, we would have a similar situation. But I guess it’s like Io is so hot that it just turned all of the water into steam, and the water is long gone. But with Europa, it’s just the right temperature.

Pamela: Right. And its hard to know what the history of each of these objects was. What we do know with Europa is we have several different models for what are the different possibilities. All of them include a layer of liquid water. Now this liquid is probably at a very small layer, just to be factually correct, also heated through radioactive decay, just like within our own Earth soil we have radioactive decay helping to keep our own planet nice and happily molten. There’s also this neat theory out there that the inside… the core of Europa… the inside is 100% tidally locked to Jupiter. It always, always has the same part of the core facing Jupiter. But for the surface, that may not be true. So the surface, this icy sphere floating on top of liquid, might be rotating at a slightly faster speed so that every 12,000… every 13,000… we’re not entirely sure—more than 12,000 years, we know… years, this shell rotates all the way around. And along with this there could be basically a tidal wave type physics built up in that liquid that’s dissipating energy in the form of heat.

Fraser: Hmmm. And that’s contributing to the melting of the ice as well. Well let’s talk a bit about the discovery, before we get too far into this ocean because, I mean, that’s the sweet prize. But first, let’s talk about the discovery because this is not brand new, but it’s definitely discovered in our lifetimes.

Pamela: Right. So we always knew there was this shiny world out there… figured it was probably ice. As we started pointing really large telescopes at it, it was realized that wow this thing somehow has a slightly existing atmosphere of oxygen. So back in the mid-90s we were detecting this atmosphere and a combination of first the Voyager missions getting images of this icy, weird, smooth world that had features that were defined by color, not by how high or low they were, and has almost no craters. The combination of all of these different features began to paint a really interesting physical picture for us.

Fraser: Right. If you look at other moons of that size or even some of the other outer Galilean moons, they have craters. So they have a rocky surface. But as you get closer into the middle, they get more and more smooth. Europa looks like it’s covered in sheets of ice, and Io is just completely resurfaced by its volcanoes.

Pamela: As near as we can tell from trying to count the almost non-existent craters, there are some… from counting these craters on Europa, it appears that the surface could be as young as 20 million years old… 80 million years old… depends on what models that you use. But this is a young surface. That means that everywhere on that surface, something has come and filled in the asteroid holes, filled in the places where rocks hit it, Kuiper Belt objects hit it. That resurfacing…. that says that somehow liquid is oozing out in some form or another.

Fraser: I wonder how that thought process went when the scientists originally saw those first photos that came back. I know that Voyager I passed Jupiter first, and it sent back less-detailed photographs. Then Voyager II got closer, got better pictures, the modern pictures that we’re all quite familiar with now, with what looks like these cracks in the surface… what did they think they were dealing with when they first saw this?

Pamela: Well, I have to admit I was a small child being forced to take naps when this was going on, but looking through the literature, there’s this leap to “oh my… insert expletive of choice…” that isn’t in the literature… but you can tell from the excitement that this idea of now we have to model ice was something that was cool and new and exciting and everyone was re-energized to look at this. Yes it was cool and shiny but otherwise just another blob of ice in the outer solar system. Trying to figure out what dynamical processes can lead to this combination of… there are places where you look at the images of the cracks and you can see where one set of cracks got shifted part-way by an intersecting crack. So imagine you have basically four cracks running parallel to one another. You bisect them with a crack, like a tic-tac-toe mark but you don’t finish drawing your tic-tac-toe field. Then you shift half of the tic-tac-toe grid but not the other, so you have this disconnect in where those four original parallel lines hit. They were seeing these crazy lines that didn’t completely line up which indicated shifting in the surface. There’s also these weird areas of ice that just basically look like chaos ensued. That’s what they call them… chaotic terrain. Just all of this mixed up mess of linear features, chaotic features, cracks, spiral features, trying to model that… that’s a mathematical nightmare to someone who hates math, but is a computer modeler’s dream project in a lot of ways.

Fraser: If you could go to Europa and land down on the surface and stand on the surface of Europa, what would this look like? Are we looking at an ice rink smooth surface? Are we looking at like a glacier field? Are we looking at dirty snow with cracks in it? What would it look like?

Pamela: It’s much more of a glacier field. It’s not perfectly smooth like a lake. There are features that are hundreds of meters high and low, up and down, where you have fissures colliding and splitting and swirliness. What’s interesting is where the cracks are, you end up with these orange-y yellow discolorations and what we think that is some sort of saline solution, magnesium sulfur… there’s some sort of a chemistry that is getting revealed in these discolorations. So if you’re standing on the surface, it’s not pure white ice in all directions, it’s not this perfect surface. It has upheavals, it has discolorations, it has all sorts of crazy patterns that do vary in scale from place to place. There are areas that are much smoother and much whiter. There are areas that are much more chaotic and bumpy, lumpy grooved. It’s not what we’re used to when we think of large plains of ice.

Fraser: Right, right. What is underneath this? You’ve got this crack on the surface… we’ve talked a bit about this ocean but let’s kind of paint a bigger picture. What do we think is going on here?

Pamela: Well the generally accepted models say that the surface ice is probably order of tens of kilometers thick. And there are models that say that it’s much thinner, that maybe it’s only 1- 2 kilometers thick… maybe even thinner than that, but the reason that we tend not to believe those thin-ice models is that where we do see craters, they dig their way in but don’t break all the way through. So that gives us a sense of the depth when you start modeling how much heat would be imparted in the ice and yadda, yadda, yadda… when you work through those calculations of the energy of the impact, and you don’t break the ice, it starts to give you hints of how thick the ice is. When we take into consideration the thickness of the ice, it looks like underneath it we’re probably looking at then maybe as much as 100 kilometer-thick water. We’re not entirely sure of the composition, clearly, you have to dig down and take samples. But in all likelihood it’s some form of salt water.

Fraser: Now would this be… this underwater ocean… be completely covering the rocky part of the moon and then it’s just that it’s got ice on top of it? Is there any place where the surface would be poking up? I guess you would see mountains, right, if it was coming through someplace…

Pamela: Well, we know that the moon isn’t 100% spherical. The universe doesn’t make planets, worlds, moons that way. But, all modeling that we have done indicates that it is mostly symmetric, and that you do have rocky core, silicate layer, roughly 100 kilometer thick water, and then on top of that a couple kilometers of ice… ten-ish kilometers of ice.

Fraser: So that’s a lot of water. Liquid water… up at the top it’s going to be cold, at the bottom it’s going to be warm… that’s pretty amazing.

Pamela: We don’t fully know what will the temperature gradients be… We don’t fully know what the currents will be. The idea that the surface ice and the core of the planet aren’t completely coupled, but the difference in rotation is order of tens of thousands of years between the two tells us that whatever currents you have aren’t planet-wide, sweeping around, carrying the surface with them. There are some sorts of currents underneath. We don’t know what sorts of convective cells might be built up in the water. So there’s all sorts of neat things that could be going on… mixing the temperatures. Yeah, it will be colder towards the surface just because you do have a layer of ice there, but we don’t know how big the differences are. That’s one of the intriguing things is for all we know there’s some form of volcanism at the bottom of all this that’s driving some sort of rift valleys like the ones we have at the bottom of our own oceans where you have underwater volcanic vents leading to amazing clusters of life. We don’t know what’s going to be underneath all of this.

Fraser: Well, let’s talk life, then. I mean, this is one of the great discoveries here on Earth is the discovery of these volcanic vents and clustered around these vents are all kinds of exotic life that derive their energy from the center of the earth, from the chemicals and the heat that’s coming out of earth. They don’t rely on the sun at all. I think before, if you cover off the light of the sun, people would say oh, there’s no life. But now we know oh no life is perfectly happy to live in a place that never sees the sun. This changes everything for Europa.

Pamela: What’s more, not only do we have this chemical, thermal conditions that we know from here on Earth are conducive to life… you have the temperature gradient, you have liquid water, you have the type of stuff that the bacteria that form the base of the food chain here on Earth’s ocean vents could similarly have found a place to evolve perhaps if there’s volcanism on Europa. But the other thing is… so if you’re hanging out on the surface of Europa… yeah, there’s a little bit of a magnetic field, but there’s still so much radiation that you die. Ice and water are great protectors of radiation. So by getting beneath this layer of ice, you’re blocking significant amounts of radiation. So you’re also creating a place that’s conducive for life due to you’re not killing it with cosmic rays, just like our own atmosphere protects us here at the surface of the earth. So there’s all of these different things that are in favor of life being able to exist. There’s a ton of scientists just dying to go drop something hot on the surface of the ice that will just melt its way through so that we can see what’s beneath all this ice.

Fraser: I mean you could, if these conditions are that, you could take life from Earth… from these deep-sea vents… some of these bacteria… and it sounds like it would do just fine in Europa.

Pamela: Well, it depends on what the chemical composition is.

Fraser: Right. Of course, you know, and it depends on the temperatures involved and whether there is energy coming out of the core of Europa into this water, but it doesn’t seem as much of a stretch as trying to make life that maybe could survive on Mars, with very low air pressure, with horrible radiation, with really cold temperatures, with no liquid water. It’s like with Europa, everything’s pretty close. It’s really tantalizing. Is there any evidence right now that there is life?

Pamela: No, we have no evidence whatsoever, just a whole lot of scientists saying yes, Mars might have in the past had life, but Europa could have it today! Stop looking on Mars! Let’s go to Europa. No evidence; just hope.

Fraser: Just hope. What would be a mission that might be able to find it? Is there any way to find evidence of life from orbit?

Pamela: Of life? Not so much.

Fraser: Like any way that organic materials with a certain signature being pushed out of the ice… leaking in vents somewhere….

Pamela: Not enough that’s believable to say… unless you find a dead frozen fish staring at you through the surface of one of these cracks…. organic molecules on their own, that’s just a possibility, but it could also be well, maybe it’s just some sort of chemical process we don’t know about yet. To get the yes, 100% we know there’s life… you have to see critters moving around or be able to sample DNA or many other extremely robust tests.

Fraser: So what would be a mission that would be able to answer that question?

Pamela: There are many different very expensive proposed missions to go drop something on the surface of Europa. Admittedly, the first few missions are probably going to simply drop something on the surface of Europa. But then after that, drop something very, very sterile… sterilized more than any surgical room here on Earth… a very sterile object, drop it, melt through the surface trailing some sort of a guide wire behind you that sends up communications to a surface part of the craft. After you drop through the ice, look around and take samples. That’s what we want to do… we want to drop stuff through the surface and give it all a good look.

Fraser: But to melt down through 100 kilometers of ice sounds like an insurmountable engineering challenge.

Pamela: It’s actually fairly easy when you start looking at all of the insanity that we go through trying to dig for oil where you have to half-way down turn right, go down another ways and turn left. Here we can just drop straight through, and it’s a matter of just melting and having enough wire. And it could be that it’s only ten kilometers thick. The water itself is a hundred kilometers thick but then the ice on top of that is probably a few to a few tens of kilometers. And that we know how to do.

Fraser: But through melting or through drilling?

Pamela: I’ve seen plans for both. It becomes a matter of how do you build something that takes the least energy. With a good radioactive pile, you just sit there and you slowly melt your way through by just letting the radiation do what it will. Drilling, that’s an energetic process where you have to be putting in energy into spinning things to get the drill, but you may be able to get something larger down by drilling.

Fraser: Oh, I see, so you would take some kind of nuclear reactor, put it on the surface, let it vent its heat and just watch it melt its way through gravity down through the ice.

Pamela: It’s a slow process, but it works. Really that’s all you care about… does it work…

Fraser: Now are there any missions even in the plans right now officially to be sent back to Europa?

Pamela: To go look at it?

Fraser: Anything! To visit it… to wave… anything.

Pamela: Yes, so we have the Europa-Jupiter System mission. This is primarily international US-ESA joint collaboration mission. It’s proposed for launch in 2016. That’s likely to slip, but it’s proposed for 2016. We’re all waiting to see what the planetary decadal survey says. If it does say let’s do this, because we do have the launch opportunity in 2016, maybe we’ll make the deadline. That’s the proposed plan right now. We’ll just have to see if it gets its funding.

Fraser: And what will its objective be? I mean, this is just an orbiter, right?

Pamela: I’ve actually hear talk of dropping stuff onto the surface of Europa. Basically they have little spacecraft that kind of reminded me of lawn darts in the talk I was in. Where you drop something down, it stabs itself into the ice, and sits there and collects data and sends signals back up to the orbiter that’s then going around Jupiter and exploring the system. So, kind of a Huygens probe for Europa.

Fraser: Right, right. And then maybe with this they can try to get a sense of the thickness of the ice… maybe if there’s an ocean the depth of the ocean… what’s underneath the ocean… I mean, it’s kind of hard to…

Pamela: Yeah, it’s mostly a seismic mission. You should be able to some sense of how thick the ice is, but beyond that they’re not going to get a whole lot of information.

Fraser: No, but I can think about the ways that they have uncovered the layers of the earth here. They use earthquakes, and they’re able to sense how earthquakes change and move through the interior of the planet. Maybe if they could, as you say, put some kind of a lawn dart, a seismograph onto the surface of Europa, maybe they can listen how moonquakes go through Europa and then try to map out the shape of the interior… which would be pretty exciting.

Pamela: And we do suspect that there should be some sort of seismic activity. So it’s just a matter of sitting there and listening and hoping you get the right type of data.

Fraser: There sure is some over on Io, so…

Pamela: Yeah, that’s for sure.

Fraser: Cool. Well, then that’s it, and we’ve talked about on our Titan show just about how Europa is an even more exciting place to search for life, and I think talking to you today… this has made me even more excited about the prospects of life on Europa. It’s just an enormous engineering challenge… way tougher than sending a probe to Titan.

Pamela: In some ways, though, it’s the type of thing that Halliburton has been training us for for a long time.

Fraser: We’ll put them to good use. We’ll get their help. We’ll find a crack team of miners and oil drillers and send them into space to find life on Europa. That would be a movie, I think. See if Bruce Willis can do it.

Pamela: Yes, yes… definitely.

Fraser: Well, thanks, Pamela.

Pamela: It’s been my pleasure. Bye-bye.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Show Notes

• Alien World Tour: The Exoplanets Around Star Gliese 581 — Space.com
• The Gliese 581 System — Universe Today
• Gliese 581 System Data – Princeton U
• Habitable Zone — PBS
• Habitable Zone — Universe Today
• Gliese 581 g: New Exoplanet is in Star’s Habitable Zone – Universe Today
• Could the Chance for Life on Gliese 581 g Really by “100%” — Universe Today
• Vent Communities on the Ocean Floor — NOAA
• Creatures of the Thermal Vents — Smithsonian/NASA
• Mathematical Probability of Life on Other Earth-like Planets — Science 2.0
• Update: Recent findings cast doubt  on whether Gliese 581g exists

This transcript is not an exact match to the audio file. It has been edited for clarity.