Mars is a world of extremes. This unassuming red world is home to the largest and tallest volcanoes in the entire Solar System. In fact, it’s not even a close contest, with Olympus Mons rising 22 km above the surrounding plains, more than twice as tall as Mount Everest. How did Mars get such big volcanoes, and how active is the planet today?
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Fraser Cain: Astronomy Cast Episode 433: Volcanoes on Mars
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, the director of CosmoQuest.
Hey, Pamela. How are you doin’?
Dr. Pamela Gay: I’m doin’ well. How are you doin’?
Fraser Cain: Good.
The final episode of 2016, I guess. But, for those who are listening to it, it’s probably already 2017. So –
Dr. Pamela Gay: It’s true. It’s true.
Fraser Cain: Happy New Year.
Dr. Pamela Gay: And, if you haven’t heard this already, that means you’re listening to the audio show and you are missing out on all of the craziness that goes on with our pre-show and with our post-show Q & A over on YouTube.
Fraser Cain: Yeah, our – Astronomy Cast has now sort of become about twice as long every episode that we do. We do it live on Fridays at 1:30 Pacific time on the YouTubes and we then do the show – it takes about half an hour – and then we stick around and answer your questions about space and astronomy and we just chat for another half hour. So, if you want to get more Astronomy Cast, you can come and check that out. Just search for Astronomy Cast on YouTube and you’ll find it. And if you want to be notified when we do our live show, just click on the little “Notification” bell and then you’ll get that announcement.
Dr. Pamela Gay: And so, we hope to see you live, where you get to see how the sausage is made –
Fraser Cain: Yeah.
Dr. Pamela Gay: – and enjoy in the insanity.
Fraser Cain: Yeah – and you get to have all your questions answered. We just stick around and answer them. So, that’s the deal: You want to watch us live; we’ll answer your questions.
Mars is a world of extremes. This unassuming red world is home to the largest and tallest volcanoes in the entire Solar System. In fact, it’s not even a close contest, with Olympus Mons rising 22 kilometers above the surrounding plains, more than twice as tall as Mount Everest. How did Mars get such big volcanoes, and how active is the planet today?
Alright. So, let’s go and sort of let people know. Let’s talk about some of these volcanoes as they exist today – and we’ll kind of blow people’s minds about the size and scale of these things.
Dr. Pamela Gay: So, you already started it with Olympus Mons, which is more than 20 kilometers high. Its caldera – that pit that, on cartoons, you’re always throwing someone sacrificially in to – that caldera pit, by itself, is 3.2 kilometers deep. And this is the biggest volcano, the biggest mountain; the biggest from the base of its formation to the top, where it’s literally making it something that comes up over the edge of the planet and is highly noticeable. Olympus Mons is just the biggest geologic feature in our solar system.
Fraser Cain: Did they know about Olympus Mons before the spacecraft explored it?
Dr. Pamela Gay: Oh, yeah.
Fraser Cain: It was visible from Earth. Okay.
Dr. Pamela Gay: So, you can readily see the entire Tharsis region; so, this is that volcanic region where you see a stripe of three beautifully aligned volcanoes and then Olympus Mons hanging off to the left, in most NASA imagery. So, north up, we have – west is where you have Olympus Mons and then you have this alignment of three volcanoes from west southwest – or south southwest, I guess – up to north northeast.
Fraser Cain: And each of these other volcanoes, on their own, are –
Dr. Pamela Gay: Big.
Fraser Cain: – incredible monster volcanoes.
Dr. Pamela Gay: Yeah. And the one that gets me is the Arsia Mons. Its caldera – this is the episode where I’m going to twist my tongue on everything. Arsia Mons, which is – when you’re looking at them, the one in the lower left – it’s 130 kilometers across on its caldera. So just that hole in the center, for those of you who speak Imperial, that’s 81 miles across. It’s 1.3 kilometers deep. So, just the caldera is an extremely impressive feature.
Fraser Cain: I’m sort of looking at a picture here on the internet and you could just barely fit Olympus Mons within France – all of France. Like, it’s like – just barely fits.
Dr. Pamela Gay: The Tharsis region on Mars, which is a pretty good-sized world – 25 percent of its surface is this Tharsis region. So a quarter of the surface of Mars is this one volcanic activity center.
For comparison, 29 percent of the Earth’s surface: Land. So there is almost as much of the surface of Mars, percentage-wise, that is one volcanic region as there is land on all of the planet, Earth.
Fraser Cain: That is a large region.
So – And one of the things as well, people always say, like, “Oh, it would be so cool to stand on the top of Olympus Mons and” you know, “and see the valley below.”
Like, the view from the top of Olympus Mons would be amazing but the – It’s so big that the planet curves away faster than the mountain. So, you literally could never see the valley below if you’re standing on the surface of Mars. You would just see the flank of the volcano and following the curvature of the planet away from you.
The view from the top of it would be, I guess, okay but all you would be seeing is just more volcano in all directions. You would not actually be able to see the rest of the planet, which is just super mind-bending. Yeah.
Dr. Pamela Gay: And these are mind-blowingly large volcanoes; in part, due to the fact that Mars has significantly lower gravity and significantly lower atmospheric pressure than we have here on Earth. So, when you combine these things, you end up with giant shield volcanoes that don’t act like shield volcanoes here on Earth.
So, if we had been able to be around when these things were doing their whole eruption thing, we would have seen at one point, on the Elysium Planitia, a volcanic plume the size of Oregon; so, this one tongue of lava the size of Oregon.
And we also would have seen massive ash plumes that aren’t normally associated with shield volcanoes here on Earth. And this is just due to the combination of – you can end up with a different gas load inside, lava of this viscosity – this runniness. All sorts of crazy things happen.
And these are also hotspot volcanoes, which we do have here on Earth. These are the kinds of volcanoes like Hawaii is this kind of volcano. But, with the hotspot volcanoes on Mars, you don’t have a big bubble of lava that’s directly below the surface; you have it coming up from much deeper down. And when it goes, it seriously goes and goes and goes and goes and goes.
Fraser Cain: Yeah.
Dr. Pamela Gay: So you don’t end up with these sporadic Icelandic-type volcanoes that go off every once in a while, briefly, you end up with millennia of going off.
Fraser Cain: Alright. Well, let’s talk about these two ideas that you just mentioned here. One is that the volcanoes on Mars are shield volcanoes. And, you know, the best example of that, of course, is the volcanoes of Hawaii, which are gigantic. We should look at, you know, Mauna Kea, Mauna Loa.
What causes a shield volcano?
Dr. Pamela Gay: The best way to think of it is, as it goes off, it just has the lava just flowing outward, forming layer upon layer upon layer, that builds up over time.
And what’s cool with this building up through layers that you see on Mars is, because you do have the lower gravity and you have a different viscosity of the lava, the lava just flows slowly for a long time. And you end up with these very shallow inclination angles, which is a fancy way for saying: It wouldn’t be terrible to bike-ride up one of these things because it’s like a 4?degree incline.
A lot of these volcanoes here on Earth – if you’ve ever gone up to the top of Mauna Kea, down in Hawaii, it is steep. The engine of your vehicle is hating you. You don’t even want to climb this thing. Here, you’re looking at much more shallow-grade mountains.
Fraser Cain: But the idea is very similar, right? That you’ve got this – It’s a certain kind of lava it’s producing that’s very viscous. Right? I think that’s the term, right? Not viscous? Hold on a second. The one that’s not thick, not – Less syrupy, right? That – So that it flows out and sort of spreads in these kind of even patterns and goes a long way. When it comes out of the – It has a low viscosity. When it comes out of the caldera and flows down the side of the mountain, it goes for a long, long way. And so it’s like it’s painting lava onto this volcano, just layer by layer by layer.
But the other thing is that it’s – they’re sticking around. You said it’s this “hotspot” idea but they’re sticking around for a tremendous amount of time. And so, over the hundreds of millions – potentially even billions of years – Mars has had plenty of time to get this lava out onto the surface and just – and really, to spread it out across the Tharsis bulge.
Dr. Pamela Gay: One of the more amazing factoids I’ve run across about the Tharsis bulge –
Fraser Cain: The Tharthith – Tharthith bulge?
Dr. Pamela Gay: About the Tharsis bulge – is it might be 4 kilometers deep and just layer upon layer of multiple generations of volcanoes. This bulge, itself, formed about 3.7 billion years ago – so this was during the Noachian period – and, as it built up, there was an earlier generation of much smaller volcanoes just kind of all over the place – before we ended up with this triumvirate of volcanoes that formed that main ridgeline – and then Olympus Mons off to the side, which is a little bit younger.
So, you have this history of – since the earliest days of Mars – this was going on and, as we talked about a little bit last week, the formation of the Tharsis bulge led to the rifting apart of the planet surface in other places.
Fraser Cain: Yeah, it cracked right open to let this sort of bulging and upwelling of volcanic material had, you know – it had an impact. And, you know – and geologists are still understanding and realizing the implications of what this did to the planet’s history, even now, and some – You know, the spacecraft are helping to get a better sense of this as well.
Are the volcanoes dead? Is Mars geologically dead?
Dr. Pamela Gay: We think so but we don’t know so. So here’s where spacecraft, like, may even become so important. I actually have to flip through my notes because I will screw up the chemicals.
So there was thought from counting craters. Folks like Gerald Neukum and his team have been counting craters and it looks like the – by crater dating – youngest volcanoes that folks have been able to identify are about 2 million years old.
But there’s this methane that keeps cropping up in the atmosphere of Mars. And if you see methane, then you either have life or you have geologic processes. So you start looking for evidence of these two things and ways to distinguish between them.
Well, if you have volcanism in the form of happily erupting volcanoes, then you’ll have, not just the methane, but you’ll also have sulfur dioxide. And studies that have looked in detail for the sulfur dioxide have not found it at all. So that seems to indicate that we don’t have active volcanoes going off.
Now, what’s interesting is there’s other ways that the environment can generate methane. Another factoid I learned prepping for this show is you can actually take carbon dioxide and water and, during an electrical storm, the electric charge in the atmosphere and the discharge of that electricity can lead to the formation of methane and then it deteriorates over time. But this is a world that has magnificent dust storms and that magnificent dust storm can generate lightning shows.
Fraser Cain: So, let’s talk a bit about the reasons why – That would be crazy. Lightning? That would be just amazing.
Let’s talk about why Mars has such big volcanoes. So this – I mean, there’s two real big processes going on here. One is the low gravity; so you can just build things bigger. You know, Mount Everest could be, you know –
Dr. Pamela Gay: Bigger.
Fraser Cain: Bigger – 1 divided by .38 times bigger. Right? Just in terms of gravity. Because Mount Everest is, like, as big as a mountain can be on Earth and you pretty much can’t get any taller than Mount Everest. But if you decrease the gravity, you can have a bigger mountain.
But Mars doesn’t have any plate tectonics.
Dr. Pamela Gay: Not the way we think of it. So, here on Earth, we readily joke that California is trying to visit Alaska as the plates move. We see the Rift Valley in Ethiopia, where Africa is literally tearing itself apart. There are distinct plates on Earth that are each doin’ their own thing, moving in their own direction, causing massive disruptions on the surface of the planet; when things that are sort of held together, like roads, cease to be held together because the earth beneath them shook.
Fraser Cain: Yes, this is my world.
Dr. Pamela Gay: This is our world.
Now, on Mars, we don’t have all of these distinct plates. There are, perhaps, two plates – maybe, kind of – on either side of the – blech –
Fraser Cain: Marineris?
Dr. Pamela Gay: Yes, on either side of Valles Marineris. Those plates aren’t well separated, aren’t extremely distinct, aren’t moving in the ways we’re used to. So, what you end up with instead, is: This is a world that had a molten core – still has somewhat of a liquid core, we believe – and heat has to escape. And via various convective forces, you end up with these hotspots and these hotspots eventually eat their way all the way through the planetary layers until they come out the surface. And this leads to prolonged volcanoes in single spots instead of these rifts like we see on Earth, that are dotted with volcanoes all along them. So –
Dr. Pamela Gay: Yeah. And anyone who’s been to Hawaii, you’ve experienced that; where you’ve seen, you know – You know, Kauai is the old one and then Oahu is a little younger and then Maui’s even younger and then the – I forget which side. The western side of the Big Island is older but then there’s active volcanoes. And that hotspot, you know – the earth is moving above that hotspot – and so it’s constantly creating new volcanoes as it goes. But really –
Dr. Pamela Gay: Whereas we also have the Pacific Rim and the area along – for instance, around Naples in Italy – these different areas on the planet, where you have strings of volcanoes. Japan is a string of volcanoes. Alaska has a string of volcanoes. These –
Fraser Cain: I live in a string of volcanoes.
Dr. Pamela Gay: You do live in a string of volcanoes.
And these are very much generated by places where either two plates are – one is ducking under the other or they’re diverging apart from one another. This is a completely different kind of volcano. Mars does not have Iceland-like volcanoes. It has Hawaii-like volcanoes.
Fraser Cain: Yes.
And so, I mean, I had heard that it is, like, maybe possible that Olympus Mons could erupt again at some point. Do you think – I mean, probably not in our lifetime, but is it, you know, between now and when the sun destroys it?
Dr. Pamela Gay: I don’t think we know enough yet.
Fraser Cain: Yeah.
Dr. Pamela Gay: And this is the cool thing about why we keep doing science, is we’re still learning to fully understand volcanoes. If we understood them better, we’d know when Katla’s going to go off next. And I am one of these people who’s just waiting for that next gigantic Katla Earth-cooling Icelandic volcano eruption that, unfortunately, it will do bad things to travel. But I’m going to ignore that and look forward to the cooling properties of what it will do to the atmosphere. We still don’t know these things.
And we also don’t have a really good understanding of the interior of Mars. We haven’t been able to distribute the kinds of probes all over its surface that will detect all of the wiggles and jiggles, the P waves and S waves that pass through the planet when it gets hit by small asteroids; when – Heck, when we hit it with probes, because this is a thing we do.
Fraser Cain: Right. So, this idea of, like, the seismograph – I mean, we’re so familiar with this little line that – You know, the little pen that’s drawing on a little line that’s going and it’s sort of drawing out the waves, the various shaking that the ground is doing. One of these does not exist on the surface of Mars. And better yet, you need multiple of these on the surface of Mars –
Dr. Pamela Gay: Right.
Fraser Cain: – mapping out, as events happen.
Dr. Pamela Gay: And we just don’t have that. And since we don’t have it, it means that we don’t have this deep understanding of: Where are the thick areas; where are the thin areas; where’s their liquid; how does vibration transfer through the surface?
So, we want to know these things and we know that Mars is constantly getting hit by things – not just the things we hit it with – because we see the new craters forming. And this is opportunity to learn about the inside of the planet and, with that information; we’ll be able to predict: Is the volcanism off forever? Is the lack of volcanic activity for 2 million years a sign that, yeah – she’s done. She’s done. We don’t know.
Fraser Cain: But this – I mean, you talked about this – you know, earlier in the show – this idea that we’re searching for methane in the atmosphere of Mars. Now, of course, the sort of one exciting idea about this is that it is life and that there is active methanogens on the surface of Mars and they’re producing methane and that’s super-awesome.
But the other idea is that there is still some kind of active volcanism that’s going on; it’s producing, you know, volcanic outgassing. And that means that the interior of the planet is still kind of, you know – partly alive; mostly dead but partly alive.
Dr. Pamela Gay: And one of the things that we see on Mars, that was part of the evidence for plate tectonics on Earth, is this striping of polarity in magnetic fields that are found fossilized in the rocks on Mars. So, just like on Earth, you’ll find things that have intrinsic magnetic fields that aren’t all lined up the exact same way because those rocks and their magnetic fields were locked into place when the pole had a different alignment than it currently has. We see similar striping of magnetic fields on Mars, so we know that that dynamics was there.
And it’s neat to think about these things but, again, we still haven’t found that sulfuric dioxide that’s evidence of active volcanoes. The place to go and look is the Elysium Planitia. This is where the most recent signs of volcanism are and, again, tongues of lava the size of Oregon. It’s kind of cool.
Fraser Cain: One of the kinds of sad things about Olympus Mons is that it’s a pretty terrible place to actually visit for spacecraft. It’s so high up that there’s no atmospheric – there’s almost no atmosphere that can be used to brake; to use the aerobraking the way they do with the current spacecraft. And, as well, it’s covered in dust.
Dr. Pamela Gay: And –
Fraser Cain: Thick layers of dust, that kind of collect as those dust storms go around the planet.
Dr. Pamela Gay: Right.
Fraser Cain: So, any – Yeah. So it would be a pretty terrible place to try and visit and explore and rove through.
Dr. Pamela Gay: Yeah. So you’d want to, first of all, try and land inside the caldera and, second of all, yeah – you have to use retrorockets. It’s the only way you’re going to land on one of these things. There’s just not enough atmosphere.
So, it’s tricky. Or we just need to build much faster-moving rovers and land one off to the side and send it climbing. But we’re not there yet. We still need a whole lot of self-driving car research to be done.
Fraser Cain: Well, I just imagine some rover – like, some kind of monster truck rover with great, big tires – trying to blast its way through this really deep, fluffy regolith as it makes its way up to the caldera and to peer over the edge. While standing on the caldera and looking towards the plains, towards the valley, would not be that interesting, looking into the caldera would be an astonishing perspective.
Dr. Pamela Gay: Right.
Fraser Cain: That, I would like to do.
Dr. Pamela Gay: Yeah, if you’ve ever been to the Grand Canyon, think Grand Canyon on all the steroids. This is kilometers deep. It’s just huge. It’s awesome and totally worth exploring.
Fraser Cain: So, we’re familiar with the main one – obviously, Olympus Mons – then the other three, which, again – each of which would be the largest volcano in the solar system if it wasn’t for Olympus Mons. Like, they just – The next – I think the No. 2 is like 20 kilometers tall. While Olympus Mons is 22, the second one is like 20 kilometers tall. So these are gigantic volcanoes.
Dr. Pamela Gay: Yeah.
Fraser Cain: But is there other volcanism on other parts of the planet? Do we only see it here –?
Dr. Pamela Gay: No.
Fraser Cain: – or are there other regions that have some evidence?
Dr. Pamela Gay: No.
So, the two big regions are the Tharsis bulge and the Elysium Planitia. But one of my other most favorite random things in the solar system, in terms of, “Wow! That’s a thing that happens” is Alba Mons. This is a volcano that is – to use the big words – antipodal to the Hellas impact. This means that if you take Mars and you do the whole “digging to China” kind of thing –
Fraser Cain: Mm-hmm.
Dr. Pamela Gay: – and put a line straight through this three-dimensional object –
Fraser Cain: Yep, yep.
Dr. Pamela Gay: – on the other side from the Hellas impact, you have this volcano. And it’s thought that possibly, the seismic waves of this magnificent impact actually caused a volcano to go off on the other side of the world.
Fraser Cain: That is mind-bending, that there were impacts that big; and that you can just imagine this kind of – these waves flowing through and then kind of coming together on the exact opposite part of the planet and then causing this kind of release of energy in the form of volcanism.
This is thought that this kind of event had happened on Earth in the past as well. There was, like, some regions that were antipodal to large potential impacts as well. Like, rippled terrain and things like that, on the Earth.
Dr. Pamela Gay: And we’ve had suspicions about some areas on Mercury but this is one of those “best examples” of Hellas on one side, cruel lonely volcano on other side – I mean, it’s not entirely lonely, it’s Mars. There’s volcanoes most places. But it’s striking and it’s awesome to think about; just that all those waves, their energy coalescing to trigger a volcano.
Fraser Cain: We see those shield volcanoes but here on Earth, we have many different varieties. We have, like, various cone volcanoes and ones that are composite volcanoes and various kinds. Do we see any more of those? Like, those really tall, spiky, peaked ones?
Dr. Pamela Gay: Nope.
Fraser Cain: We don’t see those at all?
Dr. Pamela Gay: No. Well, so first of all, the shield volcanoes have highly fluid basalts. And this is a function of – first of all, you have the magma chamber, which has a set temperature, but then you have, not just the temperature that causes the fluidity, but the composition. And it’s the composition of Mars’ lava that is this standard basalt lava that is leading, in part, to similarly composed, consistent kinds of volcanoes across the surface.
Fraser Cain: Crazy place.
Cool. Well, thank you very much, Pamela.
Dr. Pamela Gay: It’s my pleasure, Fraser.
Fraser Cain: We’ll see you next year.
Dr. Pamela Gay: See ya next year.
Male Speaker: Thank you for listening to Astronomy Cast, a non-profit resource provided by Astrosphere New Media Association, Fraser Cain and Dr. Pamela Gay. You can find show notes and transcripts for every episode at astronomycast.com. You can email us at firstname.lastname@example.org. Tweet us @astronomycast. Like us on Facebook or circle us on Google Plus.
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Duration: 29 minutes