What Martian Geology Can Teach Us About Earth

VALERIE PAYRÉ: Thank you very much for having me.

IRA FLATOW: It's nice to have. Given the stark nature of the Martian landscape versus the black, fertile ground in Iowa, I wouldn't think that there would be connected somehow. For example, if you look at pictures of Mars sent back by the rovers, you see lots of red rocks. What are they geologically? Is there something on Earth that's like them? Obviously you must be able to connect the dots here. Or the rocks here.

VALERIE PAYRÉ: Yes, that's a great question. Rocks on Mars are pretty similar, actually, to what we find on Earth. And we thought that Mars rocks were mainly basalts, looking like rocks that we find in Hawaii, for example. So lava flows all over Mars. And with the recent missions from the Curiosity Rover that is still operating at the surface of Mars today, we found more diverse volcanic rocks, including rocks that look like what are making the continents on Earth. So it was a real surprise, but it looks like Earth and Mars are pretty similar in a lot of way in terms of the geology.

IRA FLATOW: Well, when you say similar to the ways they're making the continents as here on Earth, I mean, we have plate tectonics here on Earth, right? Do they have that on Mars?

VALERIE PAYRÉ: Well it doesn't seem like it. We haven't found any proof of plate tectonics on Mars. We don't see mountains or big basins that are pretty long on Mars. So it seems like plate tectonics didn't really happen on Mars, but we do find those interesting rocks that, in composition, their chemistry looks like the chemistry of terrestrial continents.

So it raises questions of like how they formed, and that's a question that I'm working on. That it could be plate tectonics, but we don't see any proof of it on Mars, so it could be other processes, and that's what I'm trying to understand.

IRA FLATOW: Right. Because we have here on Earth, we have lots of volcanoes.

VALERIE PAYRÉ: Yes, we do.

IRA FLATOW: That bring up a lot of lava rock. Does that happen on Mars?

VALERIE PAYRÉ: It happened in the past, yes. Mars is covered of volcanic lava flows, and there were also explosive eruptions like what happened with the Mount St. Helens, for example, on Earth. So we do see a lot of traces of volcanic eruptions on Mars, but it seems like it happened a long time ago and stopped, and today, we don't have any evidence of volcanic activities.

IRA FLATOW: Let's talk about Mars and Earth in many different ways. For example, how similar are they? What about size, land mass, things like that? Gravity?

VALERIE PAYRÉ: Yes. So Mars is twice smaller than the Earth. In terms of the gravity, its gravity is also lower because of its smaller size. The atmosphere is way lower than on Earth. It's a really thin atmosphere, so even if there is wind on Mars, it would not blow away like rockets or rovers. It's not really possible. So it's different than what we have on Earth.

But otherwise, we don't have any magnetic fields on Mars as we have on Earth. So Mars seems like this planet that died a long time ago, but there is still some wind activity happening, but it's definitely not really active anymore like Earth.

IRA FLATOW: Why doesn't Mars have a magnetic field like we do?

VALERIE PAYRÉ: So it's related to the core. So on Earth, we have the magnetic field because the core is having some liquid moving, and that is creating this magnetic field around the Earth. And on Mars, because it's a way smaller planet, it cooled down way faster than on Earth. And so we think that the core on Mars is not really convecting anymore, it's not liquid anymore. And so that would prevent any magnetic field happening anymore. So it was there a long time ago, but it was shut down after less than a billion years after the formation of the planet.

IRA FLATOW: That's interesting. It almost sounds like these things are somehow connected. The lack of plate tectonics, the lack of active volcanoes, the lack of a magnetic field. Are they linked somehow?

VALERIE PAYRÉ: Yeah, kind of. Somehow it's all linked to the temperature inside Mars. So you would have plate tectonics because you have some movement inside the mantle that make plate tectonics happening. You have, in the core, some movement of liquid thanks to the heat. And on Mars, it's- again, it's a smaller planet, so everything cooled down quite rapidly.

And even though it's still hot, it's not it's not all cooled down today, but it's not hot enough to make liquid movement inside Mars. So that would prevent any volcanic eruption, any plate tectonics, and the magnetic field just shut down. So yeah, everything is related.

IRA FLATOW: Was there once an atmosphere that is now gone?

VALERIE PAYRÉ: Yeah. Well, actually, there was, yes. So we think in the first billion years after the formation of Mars, there was a thick atmosphere possibly like Earth today, but it was lost to space because of, again, the lack of magnetic field. So it's also related to the small size of Mars and the cool temperature inside.

And so all the atmosphere was ripped out by the solar wind, and now we don't have this thick atmosphere anymore. And now it's some wind happening, but there is no water- or liquid water at the surface of Mars today. And that's also related to the lack of a thick atmosphere that could maintain that.

IRA FLATOW: That is really interesting. And if you don't have plate tectonics, how does that affect the geology of what's going on in the history of the planet and what's going on now?

VALERIE PAYRÉ: It can affect a lot of things. We see on Earth, plate tectonics is- it creates all the mountains we're seeing. So it's really a cycle of a lot of elements. A cycle of water, cycle of carbon dioxide, cycle of sulfur. So there is a lot of cycle going on Earth that make life possible. And that is also thanks to plate tectonics that that's enabling this recycling happening.

So the lack of this on Mars would definitely limit at least life on Mars in the past. So we don't have any evidence of life beginning on Mars even though we are looking for something telling us that maybe it happened a long time ago, but if it started there, it would have been shut down very rapidly because there is no recycling of all of these really important elements, including water.

Without plate tectonics, life is hard to maintain on a planet. So if we want to see if there are any alien out there, plate tectonics could be a good place to start.

IRA FLATOW: I never heard that as a good clue.

VALERIE PAYRÉ: Yeah.

IRA FLATOW: Explain that a little bit more in detail.

VALERIE PAYRÉ: So it's not really my field here, but it's just that plate tectonics enable the water to be emitted to the atmosphere and then going back into the interior of the Earth. And you have this cycle of water being- going out and going inside the interior. And that enable hot temperatures and environment favorable for life.

And so we even think that maybe life on Earth started along those mid-ocean ridges, which is where the crust on Earth is being formed, and that's directly related to plate tectonic. So we could definitely be a clue. Maybe it's not the only environment, but it could be a clue.

IRA FLATOW: Right. What fascinates you most about Mars geology? What are you trying to learn from it?

VALERIE PAYRÉ: So from Mars, I'm trying to understand what the surface and the interiors are made of and how it is similar to Earth. We know that Mars a long time ago might have looked like way more Earth today, and a lot of things happened, including shutdown of the magnetic field that affected the atmosphere and then no water anymore at the surface and no volcanic activity, so it make the planet dying out.

But I'm really interested in Mars, a long time ago, after its formation, what it looked like, and if there were any processes that would tell us that maybe plate tectonics started there. Or what processes could explain the diversity of volcanic rocks we're observing on Mars.

My goal is to better understand the Earth because we don't know what the Earth looked like after its formation. We don't know how the crust was formed. We don't know exactly the first stages of plate tectonics on Earth. We have ideas and a lot of debates going on, but we don't really know because we lost a lot of information- because of plate tectonics, actually.

IRA FLATOW: So Mars is sort of like a planet that stopped?

VALERIE PAYRÉ: Yes. It stopped in terms of the interior and surface activities. Now it's mostly the wind and some impacts happening at the surface. So it's not all died, but it's still- yeah, the interior is has been shut off for sure.

IRA FLATOW: You mentioned different kinds of rocks on Mars.

VALERIE PAYRÉ: Mm-hmm.

IRA FLATOW: There are some times, we all know on Earth, veins of concentrated metals like gold or iron or copper. Do we know if there are mineral deposits like that on Mars?

VALERIE PAYRÉ: Well, actually, that's a topic I was working on during my PhD, so you're pointing that out right there.

IRA FLATOW: Well, did you find any? [LAUGHS]

VALERIE PAYRÉ: So with the with the Curiosity Rover- so it landed on Mars in 2012, and it has been traveling in this impact crater. And it was this crater, long time ago, was filled with water, so it was a lake. And what we found is those rocks that contain a huge amount of copper, actually, which is not supposed to happen- like that elevated amount of copper in there is not supposed to happen without processes that we know are occurring on Earth like hot temperature, fluids circulating through rocks, or things like that.

So finding those copper-rich rocks on Mars is definitely telling us that there are processes that we thought did not happen on Mars, but actually did, and it's very similar to what we see on Earth today. So another evidence of it.

IRA FLATOW: Hmm. So you used to think that Mars was like Hawaii where you had all this bubbling, volcanic, frothing rock until you started finding all these great minerals there and said- and saying, hey, there's something else going on here.

VALERIE PAYRÉ: Exactly, yeah. And that's some discoveries we did with the Curiosity Rover, mainly. And so it was like 10 years ago only. So up to 10 years ago, we thought it was just basalts in Hawaii all over, but it's not at all. It really looks like a lot- there are some processes that are hidden and that looks like what we have on Earth. So it's really exciting for the future.

IRA FLATOW: That is exciting. I mean, there's been a lot of talk about a Mars sample return mission.

VALERIE PAYRÉ: Yes.

IRA FLATOW: Which it looks like now may be delayed a bit. How much would you have to sample of actual Mars rock to satisfy you and change how you look at Mars or change your work?

VALERIE PAYRÉ: Could we sample all over Mars?

[LAUGHTER]

Well, I don't know-

IRA FLATOW: Would you like to go there yourself and sample it?

VALERIE PAYRÉ: That's too dangerous for me. But we need- we need more rocks for sure. So with rovers, we can do a lot of analysis over there on the ground. The problem is we cannot do any sample preparation. We cannot do what we do in our labs on Earth because it's just a robot.

And so the idea is to have these samples back from Mars to Earth, and that would be really fantastic. And to understand- to me, my main question is related to the crust on Mars and the first processes that formed it and how it evolved in the first billion years after the formation of Mars. And so to understand that, I would need some volcanic rocks that are extremely old, that are of different composition- so basaltic, but not only. More like composition matching continent on Earth.

So I would need a lot, but with maybe three or four samples, that would be sufficient. The problem is we haven't found those composition that are matching continent on Earth yet with the rover.

IRA FLATOW: Yeah.

VALERIE PAYRÉ: So we'll see.

IRA FLATOW: We have a helicopter on Mars, right? Couldn't that go out and pick up some samples and bring it back? I mean, theoretically?

VALERIE PAYRÉ: Well, so right now, the helicopter that was with the Perseverance Rover for the Mars return mission, it's not working anymore. It did its work and it's fantastic as we know that we can fly on Mars, but we cannot use it anymore to fly around, and it could do just images. So it could not grab a rock and put it close to the Rover or send it back to Earth. That was not the plan.

So what NASA wants to do is having this mission going to Mars and landing a platform where the Perseverance Rover would deliver all the samples. And if the Perseverance Rover is not working anymore, NASA is having these this helicopter that would get the samples back to the platform.

IRA FLATOW: Back in the 1970s, we sent a probe that landed on Mars- the Viking. I remember going to JPL and watching our first photos coming from the surface of Mars. And it had a little chemistry set on board to sample the soil, but it found no hard evidence of life. It's a little bit controversial to this day about the results, but what do you think? Could we or should we do the same mission all over again with a better chemistry set?

VALERIE PAYRÉ: That would be ideal, but still, I don't think, even today with way more technologies and advanced instruments, I don't think we could tell right away if life is in the sample because we need to do really advanced and complicated measurements that necessitate a lot of sample preparation. And the sample preparation in rover cannot do that.

So that's where the Mars sample return mission is really important. We want to send samples back to Earth to actually do those complicated analyzes in our lab on Earth where we can do anything we want and do the sample preparation that is required.

IRA FLATOW: Well, one last question about Mars, and it has nothing to do with Mars. And that is, what about other planets? Other planets of interest to you in our solar system. Any other ones? What do you say?

VALERIE PAYRÉ: Yeah, I'm really interested in Venus, too. So this planet is the opposite of Mars. It's really hot at the surface. The atmosphere is really thick, way thicker than on Earth. The size of Venus is similar to the size of Earth. And I really want to know what Venus is at the surface and the interior. We have no clue of it.

So we have several missions, NASA and the European Space Agency sending missions there this next decade to have actual data from there. And that's really exciting and I look forward to it.

IRA FLATOW: Wow. That is exciting because we can't really see the surface much beyond what radar shows us. That would be interesting.

VALERIE PAYRÉ: Yeah, definitely. And we know there were volcanic activities in the '90s, so it seems to be still active, so that's really exciting.

IRA FLATOW: OK. I'm signed up for- well, not going, but talking to you when we go there and come back.

VALERIE PAYRÉ: Look forward to it.

IRA FLATOW: Thank you. Dr. Valerie Payré is an Assistant Professor of Earth and Environmental Sciences at the University of Iowa in Iowa City. Thank you for taking time to be with us today.

VALERIE PAYRÉ: Thank you very much for having me.

Copyright © 2024 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday's programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/