Instant Genius - What NASA’s InSight will tell us about Mars - Bruce Banerdt

Episode Date: November 14, 2018

By drilling into the surface of Mars, NASA’s InSight mission could help us discover more about the structure of the Red Planet, and maybe help us understand the formation of other planets. Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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So that's really what we're after in this case with the Insight Mission. You're listening to the Science Focus podcast from the BBC Focus magazine team. We're the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world. Find out more at ScienceFocus.com or look out for us in your app store. Hello and welcome to the Science Focus podcast. I'm Alice Lipscomb Southwell, the production editor of BBC Focus magazine. Despite the success of missions such as opportunity and curiosity in exploring the surface of Mars, we still know relatively little about what's going on

beneath the surface of the red planet. NASA's Insight mission, which is scheduled to land on the Martian surface on the 26th of November, is hoping to change all of this. Commissioning editor Jason Ghajah spoke to Bruce Bannert, the principal investigator at the Insight Mission, about the project's history, its objectives, the technology it will be using, and what studying the internal structure of Mars can teach us about the formation of planets in general. Okay, so we launched the spacecraft back on May 5th from Vandenberg Air Force Base in California, and it's been following a trajectory to Mars since then, and it's been operating. just about flawlessly in space.

We've had really good luck with it. It's been very responsive. No idiosyncrasies like some spacecraft have. And so we've had a very smooth ride. It's going to take about six and a half months altogether to get to Mars. And we're set to land on Mars on November 26th of this year. So for those who don't know, it's going to, in total, travel, something like 500 million kilometers to reach Mars.

Is that correct? That's right. And if you actually look at the way that the orbits line up, we're actually kind of moving alongside the Earth and we're just kind of going closer and closer to Mars as we kind of orbit between Earth and the Mars. And when the orbit of the spacecraft intersects the orbit of Mars, you know, bingo, we're there.

But in the meantime, like you said, we travel a long way, about almost halfway around the sun. as we get to Mars. And when we get there, we're going to be traveling about, oh, what's 18, 20,000 kilometers per hour when we hit the top of the atmosphere. And so then the excitement starts. When we start to have to slow down, we'd like to kind of get from that point to get to kind of zero kilometers per hour when we get to the surface. So that's going to be an exciting six or seven minutes. Sure. So I think one of the things that certainly blows my mind, and I think probably a lot of our listeners too, is how on earth do you navigate remotely the lander from Earth, that incredible

distance? It's actually, it's as close as you can get to magic and still be science. So you know, you see the big parabolic dishes, you know, out in the desert in California, Spain, and Australia, we use to communicate with spacecraft deep in space. And they're able to pick up the very faint radio signals from those spacecraft. And just by measuring the precise timing of those signals, you know, when they arrive and the precise Doppler shift, the frequency shift due to the velocity of the spacecraft

with respect to Earth, they track that and maintain a record of that from Earth to Mars and are actually able to locate where the spacecraft is within a matter of meters, you know, in space and its velocity to an accuracy of millimeters per second kind of accuracy. And by tracking that and by extrapolating it forward, we can make the very small corrections in the trajectory using the very small rockets on the spacecraft to tweak it a little bit faster, a little bit slower, a little bit left, right, up down.

Of course, none of those terms actually mean anything in space, but they have the equivalent it turns to figure out, you know, which direction is going in which way it's pointing. And so by the time we get to Mars, we have to hit a target that's about 15 kilometers wide and just a few kilometers high at the top of the atmosphere. And that sounds really incredibly impossible to me, but they've shown that they can do it over and over again with previous spacecraft. So I'm putting my faith in them for this time. Yeah, so as you say, when it actually arrives at Mars, it's going to be going to be going at a fair clip.

So what sort of technology are you going to use to make sure that the landing is safe? Well, we use three different basic methods to slow the spacecraft down and land it on the surface. First, when we enter the atmosphere, the spacecraft is enclosed in what we call an aeroshell, which is something that completely goes around it. The front part of it is a heat shield, very much like the Apollo capsules that brought the astronauts back from the moon. So when it gets to the atmosphere, it just has kind of almost a flat shield that it hits the atmosphere with, and that gets extremely hot from the air friction, and some of it actually burns off, a blades off of the heat shield. And that slows it down from about, like I said, almost 20,000 kilometers per hour, down to,

a few hundred kilometers per or a few thousand kilometers per hour at which time we release a parachute at that time is still going almost twice the speed of sound so it's still going pretty fast but we have a parachute that slows it down in the upper atmosphere and brings it down to about maybe one to two kilometers above the surface and we have a radar that's kind of pinging down measuring the distance of the surface and when we're about a a kilometer and a half or so above the surface, we release the parachute and turn on our retro rockets. And then we take the last kilometer or so down on the retro rockets.

As we get close to the ground, we get slower and slower. And then by the time we touch down, we're hoping to be going no more than five or six kilometers per hour when we hit the ground about the speed of a quick walk when we actually touch down to the ground. That's amazing. So whereabouts on Mars is you going to land? And why was that area chosen?

We're landing in an area called Elysium Planitia. It's a very flat, broad volcanic plane, just about on the equator of Mars. We're only a few degrees off the equator. It's actually not very far from the Curiosity landing site. We're about two or three hundred miles north of Curiosity. Curiosity is down in a crater. wanted to be in a very flat open area to make our landing as safe as possible. And that's really why we chose. We chose it for landing safety and for surface operations.

Landing safety, we need a spot that's fairly low elevation-wise on Mars, so we have plenty of atmosphere to slow us down. Mars is a very thin atmosphere, so you need to get a lot of kind of air between you and the ground to help the parachute slow you down. So we need to be low, we need to be flat and rock-free so that when we actually touch down on the surface, we don't have any obstacles or hazards that might flip the spacecraft over. And so, and we need an area that the weather is relatively benign. We don't want a place where there's a lot of winds and storms because that's obviously not a great thing to land through. And finally, we want to be able to operate this spacecraft for a long time on the surface. It's solar powered, so we want a nice balmy location.

So we picked an equatorial region that has lots of sunlight all year round. And so it turns out that if you start putting all those different constraints on it, there's very few places on Mars that we're actually hospitable to our landing. And this turns out to be actually a really good one fortunately for us. So you just mentioned that, I understand it's going to, I understand it's going to be operational for a full Martian year, which is, that's about two Earth years? That's right. The science that we're doing, which haven't had a chance to talk about yet, but we're doing seismology primarily to probe the depths of Mars. And to do a seismic experiment

on the interior of a planet, you need to accumulate a lot of different Mars quakes, a lot of different signals. And so the longer that you stay there, the more of those signals that you can pick up. Mars is not as active as the Earth, so we need, we figured out we need at least about two years to get enough Marsquake signals in order to be able to draw the conclusions that we need to draw about the structure of the interior. That means we have to last not only through a Martian summer, which is actually, that's harsh enough. That's sort of like, you know, living in Antarctica. but we have to survive a Martian winter as well, which is really challenging. And so we've designed our spacecraft to be able to survive the conditions of a full Mars year and get the time on the search that we need to do our science.

So, yeah, you mentioned that one of the key instruments on board is a seismometer. So can you tell me a little bit about that, how it works, and what you're going to be using it for? Okay, so seismometer is an instrument that we actually use very close. commonly on the Earth, and it measures the vibrations of the surface of the Earth, and those vibrations can be from all kinds of things from, you know, if you walk by, you can feel the vibrations, or if you have a lot of wind blowing around you, if you feel vibrations. But the important thing to us are vibrations that are set up by Marsquakes, which are just like earthquakes, except they happen on Mars. So on the Earth, if you have a quake,

which is a sort of a cracking and moving, a quick motion of the Earth's crust, it's sends out waves, which are similar to sound waves, but they're traveling through the rocks instead of through the air. And when those waves reach the seismometer, the seismometer can sense those vibrations. And it's an extremely sensitive instrument. We can actually sense vibrations that are sort of on the scale of sort of atomic radius. And so we can pick up waves on the earth that have traveled all the way through the earth. Here in California, we routinely pick up earthquakes that have happened in Japan, in Southeast Asia, in Africa. And these quakes send out these signals that are affected by the rocks that they travel through.

So just like when you have sound waves that bounce off something and give you an echo, that echo tells you something about how far away that obstacle was that the sound waves that the sound waves bounced off something and give you an echo, that echo tells you something about how far away that obstacle was that the sound waves bounced off. And we use the same kind of techniques inside the earth, looking at these waves as they bounce off boundaries, such as the boundary between the rocky mantle and the iron core of the earth. And we can actually look at how they bend through the earth. They actually refract the way light waves refract through a lens. And we can go back and figure out what the properties of the material that it moved through, what the boundaries are, and put together sort of with a lot of different. different quake signals going through a lot of different directions. We can put together a 3D

representation of the deep interior of a planet. And so right now we don't really know how big the core of Mars is, how thick its crust is, what its mantle is made out of, et cetera. So that's really what we're after in this case with the Insight Mission. Sure. So you kind of mentioned some things there, but how much do we actually know about the internal structure of Mars today? Well, we We know that it's similar to the structure of the Earth and we know that it has to have an iron core because otherwise we wouldn't be able to match the density of the planet that we know from its orbital characteristics. We know that it has a crust similar to that of the Earth because of the types of rocks that it's made out of. And we measured the composition of those rocks using both orbital spectroscopy and some analysis on the – the ground using our rover instrumentation.

But we really don't know what the details of that structure are. And that's sort of key to how the planet evolved because it starts off as a, as sort of a uniform ball of a material that's very similar to carbonaceous chondrite meteorites. But then those rocks evolved, they melt and recrystallize into different forms. And so on the Earth, you know, we have a very different planet than than we have on Mars. We have a very different planet than we have on Venus. And one of the things that we want to find out or understand is how these planets evolve

from very similar beginnings to very different current situations. And Mars is kind of a perfect laboratory for that because on the Earth, most of the evidence from the very early stages of the Earth have been erased by plate tectonics, by mantle convection, and so forth. Whereas on Mars, the early processes happen and then pretty much things shut down except for a little bit of geologic rearranging of the rocks on the surface by volcanoes and meteorites. And so we should be able to look at the internal structure of Mars and extrapolate that to the very early structure of the Earth and understand how Earth got to be a habitable planet with lots of life. whereas Mars, Venus, and the other planets really went down different paths. Right. So by studying the internal structure of Mars, we can actually find out a lot more information

about planetary formation in general. Yeah, that's really our goal. I mean, what we really want to do is use Mars as kind of a window into the past of the Earth. And so our real goal is to better understand the planet that we live on. And it seems kind of counterintuitive maybe to go to another planet to learn more about our planet. But scientifically, you think of Mars as a different experiment that you can get a different set of results for. And then by looking at the differences, we can actually sort of figure out the processes that brought them to where they are today. So another of the instruments on board is a heat probe, which is actually going to borrow into the soil and take the planet's internal temperature. So what can we learn from taking the temperature of the inside of the planet?

Well, a planet is in some ways, as scientists, we think of a planet as a heat engine. And so, you know, all the activity that you see on the surface of the earth, you know, the building of mountains, the carving of valleys and canyons, all that kind of activity is driven by this heat engine inside the planet. So we have hot rocks rising from the depths. We have cold rocks sinking back down. And in the meantime, they're pushing around things on the surface that are melting magmas, causing plate tectonics. And so all this kind of activity is driven by the amount of heat inside the planet. One of the things we want to understand is how a planet loses its heat, how the Earth is still a very, you know, relatively hot and vigorous planet. whereas the moon, Mars are appear to be cooler and less geologically active.

We want to actually understand, you know, where Mars' heat engine is today, and again try to extrapolate that back to the early formation and evolution of the planet to understand how these planets diverge, how they're similar, and how they're different, and what makes them different. And one of the other main instruments is called Rise, the rotation and interior structure experiment. So could you tell me a little bit about how that works and what you're hoping to discover with that? Well, the way that Rise works is actually we use exactly the same techniques that we use to navigate the spacecraft between Earth and Mars,

except now the spacecraft is a lander sitting on the surface of Mars. So as we're tracking its position, we're actually tracking the rotation of the planet. So we're watching the planet rotate as we're watching the lander move with the navigation. system. And so by watching the planet move for about an hour, it actually traces out a little bit of an art as it rotates. And so we can then figure out where the North Pole of Mars is pointing at that instantaneous point in time. And by tracking the North Pole of Mars, we can actually watch it wobble the way of top wobbles when you spin it. And the wobbling of the planet is tied very closely to the distribution of mass, you know, where mass is concentrated.

So we know most of the mass of a planet is concentrated in its iron core. You know, iron is about three times more dense than normal rocks are. And so by figuring out how much of that mass is concentrated toward the center, we can actually figure out the size and the density or mass in the core of Mars. And that's a key parameter for a lot of things, such as the magnetic field generation, for the actual, it's related to the rate at which heat can be lost from the planet because the size of the core really is an important boundary condition

on heat loss mechanisms and on the composition of the core, because whether a core is solid or liquid, which we can also determine from this wobbling, is determined mostly by, you know, what else is dissolved in there, what other elements besides iron, such as sulfur, oxygen, carbon and so forth. And so we can actually figure out what the temperature of the core is by figuring out what its density is and relating that to the melting temperature.

So the rise experiment is really a key experiment figuring out the size and the composition of the Martian core. So there's also cameras on board. So I was wondering, do they serve any specific scientific purpose or is it just because taking pictures of the surface of Mars is really cool? Well, the main purpose we have for our cameras is to figure out how to put our instruments on the surface. Because when we land, our seismometer and our heat flow probe are bolted onto the top of the spacecraft. And so that's not the best place to measure planetary properties.

So we really need them down on the ground in the dirt. And so we have a robotic arm that can pick them up off the deck and place them on the ground within about two meters of the spacecraft. But we need a nice flat spot with no rocks on it. So we have these cameras on board in order to map out that space in front of the spacecraft and find a safe place to put our seismometer and our heat flow probe down. And then when we're done, we will definitely, you know, take a look around and see what the area looks like because it is always so cool to find, you know, another spot on Mars and see what it looks like.

So when can we, when do you think we'll be getting some results? coming through? Well, it turns out exploring the surface of a planet is kind of a slow motion process. It takes a long time to do things because you have to do things really carefully. You don't want to make any mistakes. So once we land, we'll actually have some pictures within the first few days. We'll have a set of pictures coming down. But it'll take us about another two or three weeks to sort of map out that area in front of the

spacecraft and decide where we want to put our seismometer. We hope to get it down sometime, probably somewhere between Christmas and the end of January, depending on how difficult the location turns out to be, and have our heat flow probe down maybe two to four weeks after that. So we're thinking about getting science data next spring is when we'll probably start getting it down. And then, as I said, we need to accumulate a number of Marsquakes before we can start making any inferences about the size. surface. But we'll be taking pictures before then. We also will have a weather station on our lander that will be measuring the weather on Mars, which should be very interesting, and also measuring

the magnetic field of Mars. So we'll start to get some scientific data down pretty quickly, but in order to get to our main goals of understanding the depths of the planet, that's going to take months to years to finish up. Sure. So just as one sort of fine, question. So all things go flawlessly. Everything works perfectly. What would be your dream discovery? Oh, wow. My dream discovery would probably be, you know, once we have the seismometer on the surface and all checked out and everything is quiet to have a really big Marsquake come along, you know, sort of a magnitude 7 style Marsquake, which sets the whole planet ringing and bounces waves off the, off the crust, off the core and allows us to really, you know, get a really precise picture of the deep inside

of the planet, which is something that I've just been, you know, sort of trying to work towards basically since I was in graduate school and first starting to try to study the activity on the surface of Mars. And I kept on just running up against the brick wall of not knowing how thick the crust was, which was sort of a key parameter on... all my calculations. And so this is going to be sort of a lifelong, a goal of mine, a lifelong dream come true, really, to finally understand, you know, what the thickness of the crust and the size of the core is on Mars. And I think, you know, the first time I see an encyclopedia article with

those numbers in it and realize that, you know, this is, it's our mission that actually, you know, generated those numbers, I think that's going to be, you know, just an incredible, incredible feeling. That's brilliant. Well, thanks very much for taking the time to speak to me, and I hope everything goes well with the mission, and I'm sure I speak for all of us when I say that we'll be following it very closely. Well, thanks for your good wishes, and just go ahead and go online on November 26. We'll be broadcasting the landing live from here at JPL, and tune in and share the excitement with us. We'll do. That sounds great. Thanks very much. That was Bruce Barnett talking about NASA's Insight Landers mission to map the inner core of Mars.

Thank you for listening to the Science Focus podcast. In our December issue, which is on sale now, you can find out much more about the Mars Insight mission, which will soon be arriving at the Red Planet. We also investigate the Gateway Space Station, which is currently under development. And of course, there's much, much more inside. Thank you for listening to the Science Focus podcast from the BBC Focus magazine. team. We're the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world. Find out more at ScienceFocus.com or look out for us in your app store.

This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analogue warmth. Alongside French acoustic specialist, Name creates high-end audio systems combining innovation with craftsmanship, so you can listen to music, just as the artist intended. Discover more at name audio.com.