Could A “Marsquake” Knock Down Your House?

IRA FLATOW: This is Science Friday. I’m Ira Flatow. If you stay around for later in the hour, we’re going to coach you on your application to be an astronaut. And we’re going to talk about whale migration. It’s good stuff coming up.

But first, on April 26, 2019, NASA’s Mars insight Lander recorded a sound researchers had been waiting for for months to hear.

[WHOOSHING SOUND]

Did you hear it? To me, it sounds like someone just turned up the volume on some Martian wind. But no. To NASA researchers, it was the unmistakable sound of a Mars quake. NASA’s Insight lander was launched in the spring of 2019 with a suite of instruments for studying what’s happening deep within the Martian surface, including an ultra sensitive seismometer for detecting suspected Mars quakes.

NASA recently published data from the first year of Insight’s mission. And it’s telling us things about these seismic activity of Mars and how it compares to Earth. Here to tell us more about this is Dr. Suzanne Smrekar, deputy principal investigator for the NASA Mars Insight Mission. Welcome to Science Friday.

SUZANNE SMREKAR: Thank you.

IRA FLATOW: Sure sounded like wind to me. Is that what a Mars quakes sounds like?

SUZANNE SMREKAR: It is one of Mars quakes sounds like a sped up a bit. In fact, if you played it at its natural frequency, it would be super hard to hear. You’d have to have really good speakers to get that bass sound. So that was sped up a little bit to make it easier to hear.

IRA FLATOW: And what is the quake actually? What is happening there that causes that sound?

SUZANNE SMREKAR: Right. Well, a quake is motion of a fault– so strong rock that’s broken, sliding past each other. And that generates a wave that was recorded in that sound.

IRA FLATOW: Is it generated differently than the way earthquakes are made here?

SUZANNE SMREKAR: Well, most of the quakes that we’ve heard on Mars– detected on Mars we believe are due to motion of rock. Now we have some that are very mysterious. And we are still trying to interpret really what is causing them.

It could be some kind of coupling of the wind or other atmospheric processes into the subsurface. So you know, about maybe 60% of the roughly 500 or so quakes– seismic events that we’ve recorded fall into this mysterious category. And so we’re still working to interpret really what the source of those particular quakes or seismic signatures are. But a lot of them, we believe, are due to fault motion, similar to fault motion on the Earth.

IRA FLATOW: And why are you so interested in seismic activity on Mars?

SUZANNE SMREKAR: Seismic activity gives us a window into the inside of Mars that we can’t get with any other kind of data. Really, what we want to do is understand things like, how thick is the crust? How thick is the mantle? What are the layers inside the planet?

And that really takes us back to the very early formation of Mars. All those layers were formed, we know, probably within tens of million years of the planet’s formation. So it kind of gives us a glimpse into that really early formation process.

IRA FLATOW: So we really don’t know what’s in the heart of the planet, what it’s made out of?

SUZANNE SMREKAR: We know it has a core. We know it has a crust. But determining how thick those are gives us much, much more information about what is made out of.

For example, there’s a big uncertainty in how big the core is. Being able to nail that down will tell us things about– maybe it has significant amount of sulfur in the core. And again, that tells us a lot about how the planet originally separates from a molten mass into these solid layers.

IRA FLATOW: Does it still have a molten mass inside?

SUZANNE SMREKAR: Well, we believe it does have a liquid core. But we don’t really know for sure. The measurements that have been made so far are ambiguous. And so we really want to be able to distinguish– does it have a partly solid core? Does it have a partly liquid core? And we’ll be able to do that as we acquire more data, both seismic– and for that particular question, we’re also taking other kinds of data to help us answer that question.

IRA FLATOW: Isn’t one of the big mysteries on Mars what happened to all that water on the surface? And doesn’t that have something to do with what the planet is made out of?

SUZANNE SMREKAR: It has to do with how the history of the water has evolved and also, you know, how can we see into the inside of the planet and get a sense of whether or not there’s still water in the inside. You know, the big question has been, is there still water at depth on Mars? Or has it all been lost off the top of the atmosphere?

And we hope maybe to be able to provide some information on that eventually. But you know, right now it’s still a bit ambiguous. We need to collect more data about the interior of Mars to really try to address that question.

Basically, water in the interior helps– it kind of helps disperse the seismic waves. And so we’re just beginning to get a handle on how that dispersion is happening. You know, is it because the upper part of the crust is very fractured by impact craters? Or you know, is there a real signature of [INAUDIBLE] down there?

So we’re kind of in the early days. And it’s hard to say, unequivocally, are we seeing that signature?

IRA FLATOW: Mhm. The Insight was launched in the spring of 2018, right? Not last year– I think I got it wrong in the intro.

SUZANNE SMREKAR: Yes, ’18. And we landed November 26.

IRA FLATOW: Mhm. If you were standing on Mars– like you would be on the Earth– and there was a little bit of a Mars quake, could I feel it standing on the ground?

SUZANNE SMREKAR: Not any of the quakes that we have recorded so far. We’ve recorded up to about magnitude 4. You know, it would have to be a significantly bigger one to be able to feel it if you were on the surface.

IRA FLATOW: And why haven’t we seen any big quakes? Why only the little ones?

SUZANNE SMREKAR: Excellent question. We wish we knew. Yeah, we made predictions of the number and size of quakes that we would expect to see. And so far, it is largely within our predictions, except for those bigger ones.

And you know, we are, of course, hoping that we will also see a larger quake– a magnitude 5 or so. But we haven’t so far. Does that mean that Mars is just operating in a way that we didn’t expect?

You know, it has a much stronger, thicker, strong layer than the Earth does. Maybe that is making it harder for us to– for deformation to occur and generate those larger quakes. But that’s an open question as well. And we’re hoping that, with more data collection, we’ll be able to get a better sense of, are the processes different, have we just not gotten lucky yet? But it’s a open and important question.

IRA FLATOW: Well, speaking of data collection, I know the Insight is slated to end its two-year mission soon. Couldn’t you extend it at all?

SUZANNE SMREKAR: We are busy writing a proposal to ask NASA for more money to keep the mission going. This is something that is done routinely with missions. They all, you know, start with an initial plan for the mission. And if things go well, we all ask for more money. So yeah, we’re hoping to keep going.

IRA FLATOW: The problem is you make them too well. You build the stuff too good. You know, look at the rovers, though. it went on for decades, you know?

SUZANNE SMREKAR: Yes. Yes, well, what can I say?

[LAUGHTER]

IRA FLATOW: Yeah. Let me ask you while we have a couple of more minutes. There are other planetary bodies that have quakes, like the moon. Can you compare a seismic activity on Mars compared to what goes on the moon, let’s say?

SUZANNE SMREKAR: Sure. Yeah. So the moon is the only other place besides Earth and Mars where we’ve had seismometers. And they were deployed by the Apollo astronauts.

And in fact, they weren’t sure that they were seeing quakes until, you know, something was artificially crashed into the planet and generated a quake. So we knew exactly what time that quake formed.

And the reason is that, on the moon, there’s been impact craters going on there for billions of years. And the outer part is super fragmented. And we just didn’t realize that this would have such a huge impact on what we were seeing in the seismic signature.

So we see some element of that on Mars. And so, you know, fortunately we had the example of what quakes look like on Mars to kind of give us some information about what to expect from that that scattering, broken up layer that we see to a lesser extent on Mars but see some aspects of that in the seismic record.

IRA FLATOW: Cool. So if we have a molten lava below the surface of Mars like you would suspect, why are there no volcanoes spewing out some of that stuff?

SUZANNE SMREKAR: Right. Well, you know, most of the surface is billions of years old. But there are a couple of areas– one, in particular– where volcanism has occurred in the last two to 10 million years.

And from a geologist’s standpoints, that’s like today. And so we have located a couple of quakes in that area. And you know, there could be magma tens of miles underneath the surface. And so, you know, it could still be hot and cooling and generating those quakes. But just because there’s magma deep down doesn’t mean you see it at the surface today.

IRA FLATOW: You covered this a little bit at the beginning, and a couple of people are asking the same question, does Mars have tectonic plates the way the Earth does?

SUZANNE SMREKAR: No. You know, on the Earth, tectonics is pretty much synonymous with plate tectonics because most of the deformation is caused by these rigid plates sliding past each other.

Mars doesn’t have that same series of plates that define different areas on the surface. It’s all effectively one giant plate. But it can still deform and generate quakes.

IRA FLATOW: So there are no like cracks in the surface like we have in the plates on the Earth.

SUZANNE SMREKAR: There are cracks, but they don’t go all the way through that strong layer. They don’t have boundaries that form plates. But there are certainly cracks, things that people would recognize as faults on the surface.

IRA FLATOW: All right. In 30 seconds, give me what you want to know most about Mars.

SUZANNE SMREKAR: I want to know most is, you know, what about this area where we are seeing quakes linked to relatively recent volcanism on the surface. You know, I would really love to understand why that volcanism is still there. Because most of the surface is so old, and it’s really a mystery as to why we still have quakes in that area and we may have magma at depth.

IRA FLATOW: Dr. Smrekar, you’ll come back after the launch and landing and all that stuff and talk more?

SUZANNE SMREKAR: I’d be happy to.

IRA FLATOW: OK.

[LAUGHTER]

That’s all the time we have. Dr. Suzanne Smrekar is deputy principal investigator for the NASA Insight Mission.

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