Ep. 690: Climate on Mars – From Ice Caps to Dust Storms

We’ve looked at Earth’s changing climate, now let’s see what it’s like for another world: Mars. Much looks familiar, but some of it is totally alien, from ice caps of frozen carbon dioxide to planetary dust storms that can obscure the entire world from view.


(This is an automatically generated transcript)

Fraser Cain [00:01:19] Astronomy Cast episode 690. The climate on Mars. Welcome to Astronomy Cast, a weekly facts based journey through the cosmos. We help you understand not only what we know, but how we know what we know. I’m Fraser Cain, I’m the publisher of Universe Today. With me, as always, is Doctor Pamela Gay, a senior scientist for the Planetary Science Institute and the director of Cosmic Quest. Hey, pal. How you doing? 

Pamela Gay [00:01:40] I’m doing well. And I just want to remind all of you who are like, oh, I hate ads. I hate hate ads. I’m with you. First of all, second of all, Patreon. If you join our Patreon at Patreon.com Slash Astronomy Cast, you will get a completely ad free version of this episode and all episodes for the past two years, and we’re working our way through the back catalog to make a podcast. Is advertise free as well? So that’s amazing. 

Fraser Cain [00:02:12] Yeah. 

Pamela Gay [00:02:13] Yeah, go join our Patreon. 

Fraser Cain [00:02:15] I mean, I like that model, right? That we make educational information as freely available as we can, and that means that, but then we also have a version that if a person does one of your ads and wants to support the work that we do, they can listen to it on, on Patreon. 

Pamela Gay [00:02:32] And yeah. 

Fraser Cain [00:02:34] We’re at a time when media is getting fractured that it’s harder and harder for people to find stuff that’s good and reliable, that you can. You know, trust. And I like to think that we’re one of those trusted sources. And so having an independent source of funding to pay the team to do this work, to pay our server costs, transcription services, all of that is, is wonderful. So all of you who do support us on Patreon, thank you. All of those who don’t thank them. And, and the system will continue onward. All right. We’ve looked at Earth’s changing climate. Now let’s see what it’s like for another world. Mars now much looks familiar, but some of it is totally alien. From ice caps and frozen carbon dioxide to planetary dust storms that can obscure the entire world from view. So Mars is so weird to me. And I think, like when you watched The Martian and you saw this kind of very familiar but alien landscape, when you see pictures coming from the curiosity rover, and in perseverance, you’re like, I could walk around on that. And yeah, it just feels like a desert, right? But it’s not the same as anything we have on Earth. So what is sort of like if you were to, like, give it like an overview of the climate on Mars today. What’s it like? 

Pamela Gay [00:04:07] It is the driest, easiest desert in the solar system. It makes Antarctica look like a warm, wet, habitable place because right. Iron on Mars you can have water ice, but it wants to sublimate away. It wants to go straight from ice to gas and join in the atmosphere. And as soon as those larger molecules get into the atmosphere, the sunlight is like, no magnetic field here. I’m going to get rid of you. And so you have this problem where the world could have an atmosphere, but that lack of a magnetic field and its lower gravity means every time an atmosphere tries to come into existence, the sun’s solar winds just blasted away. And this leads to this history of disappointment. We we’ve been looking at Mars and seeing these white points at its caps and starting to realize this is a geologically interesting world. Since the early 1700s, in the late 1700s, William Herschel was like that world. That world has dark oceans and bright white polar caps. And there were all these stories, these wonderful stories of the life that must be there. 

Fraser Cain [00:05:39] Right? 

Pamela Gay [00:05:40] And then we spent spacecraft and entered the era of disappointment. 

Fraser Cain [00:05:47] Right? When you think back, Percival Lowell imagining all of these canals across the surface of Mars and the, the, the Martians trying to conserve whatever water, they had to move it around the planet. And then the reality when we get the the first page Kraft going, nope. No canals. Nope. Are just just dry dust. Yeah. Cold dry dust. 

Pamela Gay [00:06:12] Yeah. It’s it’s one of these things where like from from what I was looking up the, the first time that the phrase canal was used was in 1858 for one of the dark streaks. And this was by a Jesuit monk. The Jesuits had amazing telescopes. Still do. And he was looking I it was Angelo Secchi, and he looked at this dark streak and labeled it in his hand-drawn maps as the Atlantic Canal. As the darker regions were seen as, as oceans, there was dust clouds seen in 1809. We’ve known there was weather for 200 years and and then with sharper rallies, sketches, we we entered more confusion because he labeled all of the dark things as canali, not necessarily implying that they were necessarily intelligently designed canals. But that’s kind of how Percival Lowell took it and ran and funded a bunch of science. Kudos for the funding of the science. Not so good on the alien intelligence part. 

Fraser Cain [00:07:24] I heard that now maybe I’m misremembering this, that maybe the canals on Mars matched up with the the veins in his retina. You heard that? 

Pamela Gay [00:07:36] I have heard that. And and so one of the weird things was, he saw all sorts of stuff that, like, a normal person looking through a telescope, wouldn’t see, but he was seeing it repeatedly. And how does that happen? And in trying to explain how it happens, I folks considered like, well, if you shine a bright enough light in your eye, you can see reflected your own eye banes. Essentially, this is probably happened to the eye doctor at some point. It’s unclear if that’s what happened or if it was his imagination, because he was able to map out a rotating world. And the fact that your blood vessels don’t change over 24 hours in 32 minutes, leads one to wonder exactly what was going on, and we’ll never know. He died before we got to ask. But, yeah, he saw things that no one else has seen. 

Fraser Cain [00:08:38] That’s so weird when you think about that, that he was seeing them rotate on the planet and then come back around. Yeah. And so he was so neuro, I mean, like, clearly then that doesn’t, that doesn’t hold water that, that he was just seeing features and then his paradigm realized. Yeah. Was just triggering each time. And he was he was mapping out these familiar features that just didn’t exist. Amazing. Anyway, so so let’s talk about the climate, like. Like, what are the factors that affect the climate on Mars? 

Pamela Gay [00:09:12] So Mars has a tilt that because it doesn’t have a large moon, wibble wobbles by about plus or minus. It’s a span of 12 degrees as it changes. And, and this wibbly wobbly tilt as well as a ellipticity, the amount that the orbit is, is flattened from being a sphere to being an ellipse. That also changes over time because of the effects of worlds like Jupiter. And this means that Mars actually has a change in climate. It is actually just now, we believe, coming out of an ice age that had pretty much encapsulated the world in snow up until 136,000 years ago. So over the years, the location of the ice caps, as well as the size of the ice caps has radically changed. And that’s just due to these geometric effects of of how things are, tilting over time and, everything else. 

Fraser Cain [00:10:24] So that’s like long term climate changes. I mean, it’s short term stuff too, like like seasons, DNA particles, right? 

Pamela Gay [00:10:32] Yeah. So so there’s. There’s layers to this. So you have day to night. You see, for whatever reason, we see a methane cycle from day to night where the rovers are able to detect methane, which is weird and cool. We have the seasonal effects where you see the sizes of the poles expand and contract from winter to summer. You have the dust storms that occur with the changing of the seasons. Then you have these thousands of year cycles that occur with the the changing of, of the tilt, the procession of the orbit, the changing of the ellipticity. Then you also have. These since the solar system began changes. And that’s where it really starts to be. A world that has experienced every possible climate that a cold world can experience, which is kind of awesome. 

Fraser Cain [00:11:38] Yeah. Let’s talk about some of those things that we just don’t have on Earth. You mentioned, you know, I mentioned in my introduction, carbon dioxide. Yeah. Polar ice caps, not just frozen water. How? Yeah. How do you get frozen carbon dioxide? 

Pamela Gay [00:11:54] You make it really, really cold. That that sounds super sarcastic, but, Mars average temperature is -80 Celsius. And dry ice forms when you have the the lower pressures, lower temperatures, and it will literally snow out of the atmosphere and increase the size of these poles each winter. The reason that we see these bright white poles on a world where water ice just sublimates away is they’re made of this carbon dioxide ice, dry ice. It’s the lower pressure and the lower temperatures in combination that allow us to see what we see. And what’s wild, though, is we we have a small fleet of robots at Mars, and the small fleet of robots, both in orbit and crawling around on the surface, have been able to figure out that there’s a fairly large flux of neutrons coming from beneath the surface of Mars, and that implies that there’s probably a whole lot of easily accessed hydrogen. And one of the best ways to get a whole lot of hydrogen in is to have a whole lot of water ice. And so we think that there are actually vast glaciers buried under dust that contain fresh water on Mars. And that’s just kind of cool. 

Fraser Cain [00:13:36] I mean, we know there is the the water under the carbon dioxide cap. 

Pamela Gay [00:13:42] Yes. 

Fraser Cain [00:13:42] And and there’s amazing pictures that you can see. I mean, because they’re taking pictures year after year after year, each springtime as the carbon dioxide thaws. 

Pamela Gay [00:13:54] Yeah. 

Fraser Cain [00:13:55] And sublimates, you get these bizarre features on the surface of Mars regions where in some cases, almost explosively blasting off of the surface of the planet. And, it’s quite there’s nothing like, again, there’s nothing like it on Earth than what you have on, on Mars. And then just imagine, like you’re on Mars and it’s winter, you know, you’re it’s fall, fall, winter is coming and it’s starting to snow. Carbon dioxide. 

Pamela Gay [00:14:23] Atmosphere. 

Fraser Cain [00:14:25] Yeah. Your atmosphere is starting to snow down. 

Pamela Gay [00:14:29] You get a change in density of atmosphere as the carbon dioxide snows out. That’s just. 

Fraser Cain [00:14:37] Yeah. 

Pamela Gay [00:14:38] That’s it. And so we’re not used to. 

Fraser Cain [00:14:40] And then let’s talk about the dust storms. So what is sort of driving them. 

Pamela Gay [00:14:45] So you have the temperature variations with the seasons. You have a world that doesn’t have the oceans holding on to heat the same way we have here on Earth. You have vast landscapes that are interrupted by massive volcanoes, that’s a thing, and interrupted by massive valleys. But none of these have the same temperature mediating effects that oceans and cities and everything else on Earth has. And so this can cause the entire atmosphere of the world to get enveloped in planet wide, high velocity winds that pick up the dust, that hold on to the heat, that then drive the storms further until the seasons change enough that the dust settles out of the air weeks or months later. 

Fraser Cain [00:15:38] We think about that dramatic scene in The Martian. Yeah. Where they had landed in this big dust storm came in and the wind was howling, and the the lander was about to fall over. 

Pamela Gay [00:15:48] But exact. 

Fraser Cain [00:15:50] Not real. Yeah. That’s realistic. I think I always say you couldn’t even fly a kite in a hurricane on Mars. 

Pamela Gay [00:15:58] The air I you know, I ingenuity has convinced me that someone at NASA could figure out how to build a light enough kite on a thin enough piece of not string that they could figure out how to do it. But you couldn’t fly like you’re normal. Go to the park by your kite at the 711. 

Fraser Cain [00:16:19] Kite in a hurricane. 

Pamela Gay [00:16:21] Weighs too much. 

Fraser Cain [00:16:21] Yeah, yeah. You can have hurricane speed winds, but you don’t get hurricane force winds because the atmospheric pressure is 1%. So you could stand out in a hurricane. Not seeing anything because of all that dust, but also not experience a bit of a park being sandblasted. I don’t know you. 

Pamela Gay [00:16:41] From it’s. 

Fraser Cain [00:16:41] Still being covered in dust. You be silt. 

Pamela Gay [00:16:44] Enveloped, and Mars dust is kind of nasty because it’s super, super fine dust. It’s more like the the dust. You see, if you have plaster walls that flake off plaster bits. I live in an old house. That may be a problem. I live with most of the dust in your house. To be gross for a moment is actually like skin cells and dust mites and things like that. But if you do have that super fine plaster dust that is similar to some of the talc and, and calcite and other dust that you see on Mars, and that super tiny, fine grained material can get lifted up by the light winds that they have on Mars and then settle down on solar panels, settle down on ices, and just cover everything up with this layer that protects the ice from sublimating and ruins the rovers that are trying to use solar power. 

Fraser Cain [00:17:52] The analogy that I heard that I really liked was that it’s kind of like that pollen that shows up on your car window. Yeah. Yellow springs. Yeah, the yellow stuff. Right. And you end you with normal dust. You could just like, sweep it off, but that stuff is sort of like, kind of almost like sticky, like it’s. Yeah, you can’t just you have to wash it out. Like as soon as you put water to it and some soap. Yeah, the stuff comes right off, but you can’t just brush it off. It’s and that’s sort of what that Mars dust is like. And it just collects season after season, year after year and obscures everything. That’s Mars today. But as you said, there are these larger cycles that last hundreds of thousands of years. But the tilt can be quite dramatic and not something that we have on Earth thanks to the moon. But let’s go way back. Yeah. How dramatically do we think the climate on Mars could have shifted over time? 

Pamela Gay [00:18:44] So we currently think that it is possible the 3.8 billion years ago, all of the areas that we currently refer to as the lowlands on Mars were actually under water. We see shorelines. And we think that the huge dichotomy in the elevations that we see was actually from a world that had sea level because it had seas. And over time the oceans came and went until about 3.2 billion years ago when they were there, just not as deep as they had been previously. And. As they want away. It has left this ancient seafloor exposed, essentially. Now, what’s really cool is right now curiosity rovers in Gale crater slowly but surely climbing up mount sharp, which is that central uplift in the middle of the crater. Gale Crater is old enough that it used to be a lake, and Mount Sharp is covered in the remnants of rivers and ponds and other water features that existed above sea level on this mountain, and as sea level dropped, it eroded Mount Sharp differently. And so, as curiosity rover climbs Mount Sharp, it is seeing different points in Mars history of having and not having water. 

Fraser Cain [00:20:17] And so obviously, like the temperature was higher, the air pressure must have been a little bit higher that you could get liquid water. And it is dramatic. I mean, the evidence that is coming now that we’re seeing these, this ancient sea on Mars, ancient ocean, and that you see craters that clearly overfilled with water and then had some kind of catastrophic flooding, you see flood plains, there’s evidence of alluvial flow from glaciers. Like it was a different place back then. Why did it go bad? Why don’t why don’t we have that Mars today? 

Pamela Gay [00:20:57] It’s this real issue with Mars doesn’t have a magnetic field and magnetic fields like the ones we have here on Earth. Take the particles heading in towards our world from the sun and reshape their path around our planet. Along these magnetic field lines, we can. When there’s a high enough particle flux, we can see this as aurora. And that protects us from a lot. And we also have, a thick enough atmosphere that the effects get metered out at different points. So you have the high energy UV rays get filtered out, and this combination of a magnetic field and a much thicker atmosphere means down at the surface, we don’t have the high energy light hitting the surface and doing bad things. We don’t have this constant flux of solar particles that can hit atmospheric particles and knock them into escape velocities and send them cascading away. And because we have a larger gravity, which is why we have the thicker atmosphere that protects us better, our escape velocity is a whole lot higher than Mars escape velocity. A good old fashioned oxygen molecule bouncing around in the atmosphere of Mars is a thug that is going to cause all smaller particles to leave the atmosphere, but we have that here on Earth. We don’t have hydrogen, helium floating around in our atmosphere. The issue is that oxygen molecule, while it’s being a thug that will get rid of all of the smaller molecules, it’s going to get hit by a solar ray that’s going to be a thug to it and knock it out of Mars atmosphere. So you have these particles removing things because the gravity is low and the particles can get there because of the lack of magnetic field. And then you also have just higher energy light able to hit the surface. And that destroys the ices on the surface a bit more. And it’s just in all a terrible feedback loop. 

Fraser Cain [00:23:14] And part of it though is like the moon is, is the next level of that, that the moon has even less gravity. And if you gave the moon Earth’s atmosphere. Yeah. Thickness, it would last for about 10,000 years. And then it would it would fade away. And but you look at a place like Titan that is less massive than Mars, it’s so far away from the sun that it can hold on to its atmosphere. It has a very thick atmosphere, thicker than Earth’s atmosphere. 

Pamela Gay [00:23:41] And that’s that permanent equation that we all learned in high school where pressure, volume, number of particles, and temperature are all related, whereas the temperature goes up, the velocity of the particles goes up, the particles fill a larger volume drops the temperature, the particles are moving slower, which puts them at a starting velocity further away from escape velocity. And it just all factors in together. 

Fraser Cain [00:24:07] Why do you think it’s important to study the climate of Mars? 

Pamela Gay [00:24:13] Well, we have this interesting history between Earth, Mars and Venus, where all three worlds up to about 3.5 billion years ago were ocean worlds. We think Venus was still potentially an ocean world until several hundred thousand years ago, and the first life forms on Earth were already building up detectable fossils 3.2 billion years ago on Earth. So with Mars past climate being wet and oceanic and having all of the things necessary for life, it raises this potential that someday we’re going to be able to go fossil hunting on Mars and figure out are those rocks we see? Actually, stromatolites are there. The amino acids that we detect here on Earth in ancient soils also present on Mars. Can we see a history of life which gets us that one step closer to figuring out, does life form easily or is it truly rare? So there’s that whole life argument. I personally really hope that we’re able to send something that can do legitimate fossil hunting within our lifetimes. Now, in addition to that, humans are explorers. There is something that is in the DNA of a lot of us that says we need to go see the thing, we need to go climb the mountain. We need to go dive under that water and see what is there. And we’re very good at finding ways to keep humans alive in hostile environments. Venus is a little too hostile. We’re not going there, at least not with any technology that is currently under development. But Mars is such that if you have a compression suit and a mask, you can walk around on Mars. There are days on Mars that are warmer than days on Boston. The days the Mars landers landed. It was like that. It was a nice balmy 30s on Mars. Not so in Boston. We remember that’s Fahrenheit though. 

Fraser Cain [00:26:39] So like but even like ten degrees Celsius. 15. 

Pamela Gay [00:26:43] Yeah. 

Fraser Cain [00:26:43] See us. Yeah, yeah. But you need that pressure suit and you need that oxygen, but you don’t need the heater briefly. 

Pamela Gay [00:26:52] You don’t need. So the kinds of thermal suits that folks use when they’re in Antarctica spending too long outside those would work for Mars for the most part, because -80 is is not something we see very often on Earth, but it’s the kind of thing that we know how to design for, right? 

Fraser Cain [00:27:13] During summer. During the day. 

Pamela Gay [00:27:15] Yeah. 

Fraser Cain [00:27:16] Wear a nice suit. And you, you know, a nice warming outfit. And you and you’d be all right with the button. You need the pressure suit and you need the supplementary atmosphere. Well, that was super fun. And, thank you, Pamela, and we’ll see you next week. 

Pamela Gay [00:27:32] And thank you, Fraser, and thank you to all of you out there who have already supported us through Patreon. You you are why we are here, why we have transcripts, why we have somebody who isn’t me editing our audio. And really, you don’t want to experience that. So, what you do allows us to make things better for you. This week, I would like to thank. And I’m going to read these as fast as I can, so forgive me. Jordan Young, Steven Veitch, Jeanette Wenk, boy, Andre Lovell, Andrew David Throg by Brian Cagle, boogie net, Gerhard Schweitzer, David Amy zang, buzz parsec. Zero. Chill, Greg. Davis, Laura. Carlson, les. Howard, Robert. Plasma, Joe. Holstein, Gordon. Doers. Adam. Andes. Brown, Richard. Drum, Alexis. Cody. Nietzsche, hail, Botkin. Wanderer and 101 Felix. Goot, Kim Barron, Tushar McKinney, William Andrews Gold, Roland Vollmer, Dom Jeff Collins, Simon Parton, Kellyanne and David Parker, Jeremy Kerwin, Stuart Miles, slug, Harold. Border, Hagan, Marco, RC, Daniel, loosely, Scott Bieber, Matthew Horstman, your guy Ivanov, and David Gates and I will be reading names slower in October, so thank you for your patience. 

Fraser Cain [00:28:55] Unless everybody signs up as a patron and then. 

Pamela Gay [00:28:58] You just, you know, if you want. 

Fraser Cain [00:28:59] To hear Pamela, have to struggle through an enormous number of names as quickly as she can. Join our Patreon patron of the comments. Just want to be cast. 

Pamela Gay [00:29:07] Yeah. 

Fraser Cain [00:29:08] Thanks everybody this week. 

Pamela Gay [00:29:10] Buh bye everyone! Astronomy cast is a joint product of the Universe Today and the Planetary Science Institute. Astronomy cast is released under a Creative Commons Attribution license. So love it, share it, and remix it, but please credit it to our hosts, Fraser Cain and Doctor Pamela Gay. You can get more information on today’s show topic on our website. Astronomy. Cars.com. This episode was brought to you. Thanks to our generous patrons on Patreon. If you want to help keep the show going, please consider joining our community at Patreon.com Slash Astronomy Cast. Not only do you help us pay our producers a fair wage, you will also get special access to content right in your inbox and invites to online events. We are so grateful to all of you who have joined our Patreon community already. Anyways, keep looking up. This has been Astronomy Cast. 

Show Notes

Mars Climate Orbiter (Wikipedia entry)

1700s – NASA Mars (NASA Mars via Wayback Machine)

1800s – NASA Mars (NASA Mars via Wayback Machine)

Mars Used To Look More White Than Red (William Herkewitz, Popular Mechanics)

Dust Storms Linked to Gas Escape from Mars Atmosphere (JPL, NASA via Wayback Machine)

Escape from Mars: How water fled the red planet (Mikayla Mace Kelley, University of Arizona, Phys.org via Wayback Machine)

Martian impact craters and emplacement of ejecta by surface flow – Carr – 1977 (M. H. Carr et all, 1977, Journal of Geophysical Research, volume 82, issue 28, Wiley Online Library via AGU)

The case for rainfall on a warm, wet early Mars – Craddock – 2002 (Robert A. Craddock and Alan D. Howard, 2002, Journal of Geophysical Research: Planets, volume 107, issue E11, Wiley Online Library via AGU)

Early Mars Climate Models – Haberle – 1998 (Robert M. Haberle, 1998, Journal of Geophysical Research: Planets, volume 103, issue E12, Wiley Online Library via AGU)