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Digging In: When Rovers Get Dirt on Mars - S4E11

Season 4Episode 11Jan 12, 2023

Aaron Yazzie and others explain how, by scooping dirt and drilling rocks, rovers are digging deeper into the mysteries of Mars.

On a Mission artwork

On a Mission artwork


Apollo 15 astronaut Dave Scott: Okay, Joe. I’m picking up the drill now.Mission Control (Joe Allen): Roger, Dave.

Narrator:Apollo astronauts conducted the first deep-drilling operation on the Moon in 1971.

Dave Scott: It works!Mission Control (Joe Allen): Beautiful. And, for goodness sakes, hang on to it there. Don’t throw it.Dave Scott: Yeah, man. You’d better believe.


Narrator:Previous robotic missions had burrowed into the lunar surface – NASA’s Surveyors 3 and 7 dug shallow trenches with a scoop in the late 1960s, and in 1970 the Soviet Luna 16 lander drilled a hole about a foot deep.

The Apollo 15 mission’s Lunar Surface Drill was designed to carve out a core of rock up to 10 feet, or 3 meters down. The battery-powered drill worked well until astronauts Dave Scott and Jim Irwin tried to pull their rock core out of the ground.

[1:02] Dave Scott: Ahhh! (heavy breathing) Nope, that doesn’t look right either. Let’s go the other way. Man, how did that treadle get like that? (heavy breathing)Apollo 15 astronaut Jim Irwin: It’s moving.Dave Scott: Yeah.Jim Irwin: I think it’s broken.Dave Scott: I think I got it. It’s really jammed.Jim Irwin: See if I can get it out.Dave Scott:Work it out towards you…

Narrator: Part of the problem was a vise that was supposed to hold onto the core had been installed backwards, and in that configuration, the vise couldn’t provide the necessary grip.

[2:06] Dave Scott: The vise doesn’t work, at all! I’ll have to have you hold it, the… It’s been an hour and 15 minutes into it already, we’re still fiddling with this thing.

Narrator:After much effort, they were able to retrieve the rock core, and later modifications to the drill made it easier for the Apollo 16 and 17 astronauts to extract their core samples. These long tubes of lunar rock were desired by scientists who wanted to understand the history of the Moon, because the deeper a rock is below the surface, the farther back in time the rock has presumably formed.

Dave Scott: Hey, Joe, you never did tell me that drill was that important. Just tell me that it’s that important, and then I’ll feel a lot better.[3:02] Mission Control (Joe Allen): It’s that important, Dave.Dave Scott: Okay. Good. Because then I don’t feel like I wasted so much time.Mission Control (Joe Allen): No, quite seriously, Dave and Jim, that’s undoubtedly the deepest sample we’ll have out of the Moon for perhaps as long as the Moon itself has been there.


Narrator:Apollo astronauts collected more shallow lunar samples, up to 2 feet, or 70 centimeters deep, using a tube that could either be pushed by hand into softer ground, or hammered into harder ground.

The astronauts also picked up rocks off the surface of the Moon. When the Apollo 15 astronauts explored their landing site – a volcanic plain bordered by 15,000-foot-tall mountains and a deep channel carved out by ancient lava flows – they found a lot of interesting rocks.

[4:04] Dave Scott: I’ve got to admit it really looks green to me, too, Jim, but I can’t believe it’s green.Jim Irwin:Oh, it’s a good story.Dave Scott: Something about green cheese? (Jim laughs) Who’d ever believe it?

Narrator:Scientists had selected this geologically varied site, known as Hadley–Apennine, in the hopes that rocks from beneath the Moon’s surface would be exposed and easier to access.

Jim Irwin: I hope it is green when we get it home.Dave Scott: Yeah. Oh, my!Jim Irwin: It is green!Dave Scott: It is green.Jim Irwin: I told you it was green!Dave Scott: You’re right! Ooh! Fantastic. Hey hold this! Wait a minute, I can’t put this into the bag yet; I got to look at this. This has got to be something. Again. Man, that looks almost…No, it’s gray. The visor makes it green, Jim. It’s gray. (laughs) It’s a different shade of gray.

[5:16] Narrator: The Apollo astronauts were trained in geology – before heading to the Moon, they’d visited various locations on Earth to learn how to spot the types of rock that provide telling historical details, such as the crystalline mineral plagioclase.

Jim Irwin: Oh, man!Dave Scott:Oh, boy!Jim Irwin: I got…Dave Scott: Look at that.Jim Irwin: Look at the glint!Dave Scott: Aaah!Jim Irwin: Almost see twinning in there!Dave Scott: Guess what we just found. Guess what we just found! I think we found what we came for.Jim Irwin: Crystalline rock, huh?Dave Scott: Yes, sir. You better believe it.Mission Control (Joe Allen): Yes, sir.Dave Scott: Look at the plage in there.Jim Irwin: Yeah.Dave Scott: Almost all plage.

Narrator: Because “plage” – or plagioclase – is often the first mineral to crystallize from cooling primitive magma, reporters following the mission dubbed their find the “Genesis Rock” – a remnant from the Moon’s birth. Later analysis, however, showed the rock is about 4 billion years old, which is too young, by half a billion years, to be a part of the Moon’s primordial crust.

[6:16]The Genesis Rock does date to a time known as the “Late Heavy Bombardment,” when the Moon, Earth, and other solar system planets were pummeled by asteroids between 4.1 and 3.8 billion years ago. Another rock found on the Moon that dates from this period is a piece of Earth that was thrown out by a massive impact event. Such remnants from the far-distant past are rare on our active planet, which continually recycles rocks as tectonic plates shift and slide along the hot magma beneath our crust, but scientists think the quiet Moon could be a cold storage for many such time-capsules of the ancient Earth.

[7:00] In all, the Apollo astronauts brought 842 pounds, or 382 kilograms of lunar rocks and dirt to Earth, and these pieces of the Moon are still being studied, yielding new findings 50 years after they were gathered.

So what, you might wonder, does any of this have to do with Mars rovers? The Moon and Mars are both dry, dusty worlds that present similar challenges to exploration. And like the Apollo astronauts, the rovers on Mars today are examining and drilling rocks to reveal new details about the ancient past, and even preparing to send some of those rocks to Earth.

It’s time to go digging with rovers on Mars.

(intro music)

[8:17] Narrator: Welcome to “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory. I’m Leslie Mullen. In this fourth season, we’ve been following in the tracks of rovers on Mars. Those tracks in the dry Martian dirt aren’t very deep, but over the past 25 years of Mars rover exploration, we’ve devised better tools to delve into the Red Planet.

This is episode 11: Digging In: When Rovers Get Dirt on Mars.


Narrator: Some of the robotic missions that have dug into Mars have been landers, not rovers. NASA’s Viking landers that arrived in 1976 scooped up Martian soil, also known as “regolith,” and so did NASA’s Phoenix lander in 2008. Although Mars is generally bone-dry, the Phoenix lander’s site near the Martian North Pole also had clay soil the consistency of thick mud, which could get stuck in the lander’s scoop.

[9:20] A drill can dig deeper than a scoop, but it’s also more complicated. Engineers tested a drill while developing the first Mars rover, toaster-oven-sized Sojourner that landed on Mars in 1997, but that drill ultimately wasn’t part of the mission, partly because the drill’s vibrations caused the onboard computer to crash.

The larger golf-cart-sized Mars Exploration Rovers, Spirit and Opportunity, which arrived on Mars in 2004, each wielded a rock abrasion tool known as the RAT, with grinding teeth that gnawed on the surface of a rock.

The car-sized Curiosity rover, which arrived on Mars in 2012 and is still operating today, has a hefty robotic arm with a block-like fist, called a turret, that holds the first Mars rover drill. Like the Apollo astronauts, Curiosity uses a rotary percussive drill. Here’s JPL engineer Aaron Yazzie.

[10:21] Aaron Yazzie:What that means is that not only does it rotate like a drill bit does to eat through the rock, but it also percusses. So there’s a little mechanism in there that’s doing little hammers on the back of the bit and sort of making it act like a chisel in the rock. And that percussion motion is actually what’s really doing all the work to help us advance through the rock, and the rotation is just allowing us to place the teeth in a different location each time we hit it.

(sound effect: Perseverance rotary percussion drill)

Narrator: Aaron helped make sure the Curiosity drill design worked before it was added to the rover. But because the drill that was being sent to Mars needed to stay pristine, they used an identical copy for many of the tests.

[11:05] Aaron Yazzie:At the same time that we’re building our flight unit, the one that’s going to fly to Mars, we’ll build another one, a replica of it, that has the same design and everything. We just build them side by side. That other unit we’ll usually dedicate to qualification testing. They call it the QM model, the qualification model.

So the qualification model dirty testbed, it’s a stage of testing that we do in this giant room and there’s this platform that you can mount all of your hardware to. And this environmental chamber, once you close it up, you can pump out all the air and take it to a very low pressure that’s similar to Mars’s pressure. You can change the temperature, and so we usually take it cold to mimic Mars’s cold temperature. And then you can even backfill it if you want it to. We can backfill it with CO2, or usually we use nitrogen – that mimics the drier air that Mars has. And then we actually find rocks that we can put in there with it. And so, we have everything that you need to mimic what you’re feeling on Mars. And we just test and test and test, to make sure that we have thought through every scenario. This is where we get our first feeling of how it’s going to perform in a very dusty environment.

[12:15] I was a young engineer then, so I was setting up tests, executing tests. We put the entire drill and turret inside of this chamber and were able to drill into rocks and scoop up sand. Curiosity has a scoop, and it also has a drill that its purpose is to turn the rock into powder, as opposed to preserving a nice rock core.

Narrator: The Curiosity rover needs to chew rocks down into powder to get an elemental taste. As Curiosity drills, the rock powder collects in its mouth – a sample tube that extends over the drill bit – and the rotation of the drill pushes that powder into a sort of gullet so that larger particles can be sieved out. This drill sampling system, known as CHIMRA, or Collection and Handling for In-Situ Martian Rock Analysis, makes sure Curiosity swallows only the finest grains so they can be digested by one of the rover’s two stomachs: either the SAM instrument, which super-cooks the dust down into molecular vapor, or the CheMin instrument, which uses X-rays to identify the rock’s minerals.

[13:25] Curiosity’s first drilling operation on Mars in 2013 was a big moment for rover exploration. Here’s JPL engineer Louise Jandura speaking at a NASA teleconference that marked the event.

Louise Jandura: This is the first time any robot, fixed or mobile, has drilled into a rock to collect a sample on Mars. In fact, this is the first time any rover has drilled into a rock to collect a sample anywhere but on Earth. In the five-decade history of the Space Age, this is indeed a rare event.

Narrator: During the same teleconference, JPL engineer Dan Limonadi mentioned an issue with a CHIMRA sieve used to filter out larger rock particles. The issue was not with Curiosity, but with one of the identical test units that made sure the drilling system worked, and also is used to troubleshoot any issues that may happen on Mars.

[14:17] Daniel Limonadi: What’s specifically happening is, on one of the Earth test units, those edge welds are popping, and slowly unzipping the sieve from the primary structure in CHIMRA.

Narrator: Aaron helped look into why the welds meant to hold the sieve in place were popping off on the test unit, and also determine whether those welds might be in danger of coming loose on Curiosity.

Aaron Yazzie:So we had to do this giant investigation to use the mechanism. And then between each time we would use it, we would have to go in with this basically like microscopic camera and take a picture of every single weld. And there’s like 40 to 50 welds on this little tiny piece of hardware, and it was very tedious. And so, we finally got through that whole thing, was able to realize that it’s not as big of a threat as we thought it would be.

[15:06] And then at the end of that campaign, we had a big party, our team, and we made a piñata that was basically like the sieve hardware. And then we took turns whacking away at it to break all the welds on the piñata. (laughs)

(sound effect: party with piñata)

Narrator: That piñata may not have lasted long, but Curiosity’s sieve welds held firm. Three years later, though, the rover’s drill developed an entirely different problem. Here’s Abigail Fraeman, deputy project scientist for Curiosity.

Abigail Fraeman:So the way the drill works… is supposed to work, is there’s actually two prongs that we would place on the surface to make sure the drill was really stable, and then we would have a, it’s called the “drill feed mechanism” that would extend the drill bit into the surface so we could drill into the surface to collect our rock samples.

[16:02] Narrator:If Curiosity were a dog, then the two prongs would be its front paws placed on either side of a food dish, and the drill feed mechanism would be the dog’s mouth moving down to eat its dinner. One day, the rover placed its paws as usual, but then made no move to eat the rocky meal in front of it.

Abigail Fraeman:That mechanism that is used to extend the drill broke. And we got very concerned that we would not be able to use the drill anymore, and we would not be able to collect samples and analyze them. And so that was pretty scary.

But the engineers put their pencils to their papers and started thinking about, well, how can we maybe use the drill in a way that it wasn’t designed to be used, that we can still collect samples and still make measurements with these instruments. And they actually figured out a way to get the drill fully extended and then drill into the rock, kind of in the same way that you would use a power drill, drilling into the wall, where instead of having these stabilizers that made sure everything was really perfect, the rover itself could sense, “OK, am I going in perfectly straight into this rock? Am I at an angle? Do I need to correct this?”

[17:13] Narrator:The engineers essentially transformed the drill from a dog into a giraffe, where the extended mouth is guided by a long neck – the rover’s robotic arm.

Abigail Fraeman:And so, we can now do this free-hand drilling. And that was really successful. And we’ve now sampled more rocks using this new way of drilling than we did sample rocks using the way the drill was originally designed to be used.

Narrator: While Curiosity started to drill in this new way, a new drill was being developed for the next Mars rover, Perseverance. This again would be a rotary percussive drill, but instead of powdering the rock like Curiosity does, Perseverance would collect whole rock cores, like the astronauts did on the Moon.

[18:01] Perseverance uses a computer algorithm to substitute for the human touch, sensing if the drill is moving too slow or too fast through a rock and then making needed adjustments. Aaron helped develop this drill for Perseverance.

Aaron Yazzie:We can tune in how fast we rotate, how hard we hit it with a percussion mechanism, how quickly we advance forward our feed into the rock. Those three parameters are the things that we change every time we encounter a new rock, whether it’s a very soft rock or a very hard rock. And we’re hoping that by tuning in those parameters, we can preserve the whole mechanism, but also preserve the life of the bit.

We sent three different types of drill bits to Mars. One of them is what we call a regolith bit, to pick up loose rocky material or sand. Another type is the abrading bits, to just drill a very shallow hole, maybe about two and a half inches in diameter, and at a depth of only maybe 5 to 10 millimeters. What we’re really trying to do with those bits is just remove the top layer of a rock, which maybe has been weathered or oxidized by the Sun. And once we get past that layer, we have a nice, pristine flat abrasion that we can then use our science instruments to go in and investigate. And so that’s what the abrasion bits are used for.

[19:23] And the final drill bit that we have is the workhorse of this whole thing, the coring bits. So the coring bits drill into a rock and extract a piece of that rock, a nice cylinder of rock that’s about the size of a piece of chalk. And it’ll save that right inside of the sample tube. And that’s how we gather our rock core samples.


Narrator: Perseverance arrived on Mars in 2021 and tried to collect its first rock core that August. The drill ended up pulverizing what turned out to be a very weak rock, and none of it ended up in the sample tube. But the tube wasn’t technically empty – it was full of Mars air.

[20:03] This sample of pure Martian atmosphere will provide an interesting comparison to the rover’s “witness” tubes that also are opened, exposed to the air, and then sealed without collecting any rocks or regolith. Meant to be a check against spacecraft contamination, the five witness tubes were pre-loaded with gases released by materials that make up the rover, or propulsion chemicals from the rover’s landing system, to see if any chemical reactions occur after being opened.

The second rock Perseverance drilled was made of tougher stuff, and since then the rover has collected many rock cores. In all, Perseverance has 43 sample tubes, and the goal is to one day send them to Earth on a future mission known as “Mars Sample Return.” To make sure its teeth hold out as Perseverance digs for its buried treasure in Mars rocks, the rover carries six coring bits.

[21:01] Aaron Yazzie:Knowing that we have to collect between 30 and 40 samples, we wanted to make sure that we weren’t going to wear out any of our bits before we got to that really interesting rock that we wanted to drill.

Narrator: Perseverance is digging into a part of Mars that may have once been a lake billions of years ago. Scientists are looking here for any evidence that life once existed on Mars, since life on Earth is closely tied to water. The team had to make sure the drilling equipment was the cleanest ever created, because if even the tiniest Earth microbe found its way onto a drill bit, that could introduce false evidence of life in the Mars rock samples.

Aaron Yazzie:The drill bits went through several processes to make sure that they were clean enough to handle our rock samples. So not only did they go through a level of cleaning, but we had to make sure we removed certain layers that, during the machining process, could get covered in oils and could impart certain layers of what they call a recast layer. We had to do some etching to remove all that. We had to do a passivation step to make sure that these bits weren’t going to get rusted, basically, when we had them on Mars.

[22:12] And the final step for all the drill bits was to coat them in titanium nitride. Titanium nitride is actually gold in color when you put it on. And its main purpose was to make sure that contaminants didn’t stick to those surfaces. They actually put titanium nitride on a lot of drilling equipment here on Earth because it has some properties that helps prevent wear, and so it’s a nice hard layer and it doesn’t collect particles.

So it was primarily for cleanliness reasons that we coated it in titanium nitride. But the nice thing that came out of it is that they’re beautiful. (laughs) They’re these beautiful gold shiny bits that just look so futuristic. It’s awesome.

Narrator: The quest to create the cleanest drill ever known meant the team had to take extreme precautions.

[23:02] Aaron Yazzie:The project came up with some very strict rules that we had to follow for contamination control and planetary protection. Not only did our hardware have to get cleaned multiple times and tested multiple times to ensure that it was at the right cleanliness level, but we, as the humans that were working on this hardware, had to make sure that we were also very clean, that we’re not accidentally imparting human DNA, or cat DNA because you have pet hair on you or something. You don’t want to accidentally give them a false positive on this scientific discovery.

And so, we went into a pretty high-level clean room, but that was just our changing room. (laughs) So we got ready in a full bunny suit, and we have a head covering, a mouth covering, and feet covering, and we’re wearing a set of gloves. That’s the first layer bunny suit. And then in that clean room, we then put on another layer of a sterile smock on top of our bunny suit, another layer of sterile gloves on top of our gloves, and then we added goggles to it, so that we could go into this very, very clean room where all of our hardware was stored.

[24:06] And the people inside the bunny suit, we couldn’t use any products that might have a scent to it. There was no cologne or anything like that allowed. There was no hair products, like hair gel. There was no makeup allowed. And one of the funny things, because of all these requirements on the types of products you can use and accidentally imparting some kind of moisture or foreign product onto the parts, we would always joke with each other, even during the craziest, the busiest moments of our project, that there’s no crying allowed in the clean room, because your tears might contaminate the parts.

Narrator: Any evidence of life beyond Earth, any proof that we’re not alone in the universe, would be deeply moving. We got a taste of that in 1996, when NASA scientists published a paper saying they found traces of fossilized bacteria inside a meteorite that had come from Mars.

[25:00] President William J. Clinton: I’m glad to be joined by my science and technology adviser, Dr. Jack Gibbons, to make a few comments about today’s announcement by NASA…

Narrator: The U.S. President at the time, Bill Clinton, made a speech about the study, noting that more scrutiny was needed of this Mars meteorite. This ancient bit of Martian crust was blasted off of Mars by a meteor impact 17 million years ago, and the rock had a long and lonely journey through space before intersecting with our planet. It landed in Antarctica and lay there for 13,000 years, just one more rock among many in the icy landscape, before it was scooped up by meteorite hunters.

President William J. Clinton: Iam determined that the American space program will put its full intellectual power and technological prowess behind the search for further evidence of life on Mars.

Narrator: Since then, multiple studies have shown that the microscopic features in question could have been the result of non-living geological and chemical processes. What’s undeniable, though, is that this rock from Mars has loomed large in the discussion of what could be considered proof of life in ancient rocks. And that, in turn, has influenced what kinds of instruments scientists have wanted to send to Mars.

[26:21] Here’s Katie Stack Morgan, deputy project scientist for the Perseverance rover.

Katie Stack Morgan:So on Perseverance, we have two really new and exciting mapping instruments on the arm or the turret of the rover. And these instruments are able to map, at very fine scales, where the organics are in the rock, and where this element is or that element, or where these minerals are.

By combining those kinds of datasets is often how we make a case that something we see in rocks are potential biosignatures here on Earth, when we look at Earth rocks, looking for patterns in the composition of rocks or their textures that are something that maybe life had a role in. And so, we’re using the same kind of techniques with the Perseverance rover that we use in the laboratory here on Earth.

[27:07] But it comes with a tradeoff. The sensitivity of the instruments we bring to Mars aren’t quite as good as the instruments we have here in the labs on Earth, or even necessarily as precise as some of the instrumentation that we have on Curiosity. But of course, those samples that Curiosity looks at, well, they’ll never come back. We’ll never know more about them than what Curiosity can tell us about them on the surface today.

And so, that resulted in a need for different instrumentation on that mission, compared to Perseverance, which in a way is a reconnaissance for biosignatures, to give us the best sense of whether we may have biosignatures, but knowing that those samples will come back to Earth and we can look at them more closely.

Narrator: Both the Curiosity and Perseverance rovers have found organics on Mars – molecular combinations of hydrogen, carbon and oxygen which, on Earth, we often associate with life. But organics also can arise from non-living processes. By learning more about the Martian environment, scientists hope to create a fuller picture of how such organics connect to the flow of water and volcanic lava in the ancient past.

[28:14] Whatever is found once we have Perseverance’s samples in hand, those Mars rocks will likely be far older than most of the rocks on our own world.

Katie Stack Morgan:I truly believe that Mars is the best place to look for signs of ancient life in the solar system, perhaps even better than our own planet, in the sense that we don’t have a particularly well-preserved record of the earliest solar system time because of plate tectonics, and we’re constantly recycling our own crust here on Earth.

Whereas Mars has a beautiful record of that period of time when life was emerging in the solar system. And so, if we want to get to the bottom of, “was there life elsewhere beyond Earth, when and how did that evolve?” I think Mars gives us a chance to answer those questions.


[29:11] Narrator: Even though Mars is an alien planet that, in a way, is frozen in time, Aaron says its landscape can seem very familiar.

Aaron Yazzie:It’s no surprise that the rocks that we’re finding on Mars are very similar to rocks that we might find here on Earth. In fact, when we’re looking for rocks that we want to test that are similar to what we find on Mars, we go looking for them in the deserts of California and the deserts of Nevada.

When I go back home to talk about my job, I like to share the similarities between the rocks we might find on Mars and the ones that we find near the Navajo Nation. It’s things like mudstones and sandstones, and volcanic rock – basalts. All of these types of rocks were made because of different geological events that happened over billions of years, and the same forces that create these rock materials on Mars are the same ones that created them here on Earth, like the way that water flows and erodes, and the way that wind erodes, and the way that we have volcanic activity. Mars has marsquakes, just like we have earthquakes. So all of these big natural phenomena that shape the deserts on Mars are the same ones that shape the deserts here on Earth.

[30:26] Narrator: Aaron’s Navajo heritage came in handy when naming some of the features of Jezero Crater, that part of the Martian desert where Perseverance is exploring.

Aaron Yazzie:When the science team for Perseverance was preparing for this mission, they wanted to come up with a way to identify different science targets. These were going to be like rock targets that they might study using all the science instruments on Perseverance. And in the past, like with Curiosity and other missions, they’ve come up with different themes, and they use that theme to sort of assign different names to different things.

And they decided for this mission, they were going to take the landing area within Jezero Crater that Perseverance was going to be working, split it up into a bunch of quadrants that are maybe about three-quarters-of-a-mile squares, and assign all these different quadrants with different national parks and national monuments that are located in the U.S. and around the world.

[31:22] And so, it just so happened, fate would have it, that Perseverance landed right in the square that was named after Canyon de Chelly National Monument, a canyon that’s located right in the heart of the Navajo Nation. It’s a center for a lot of traditional stories that we have, but also is an important part of our history. Around the time that we were at war with the U.S. government, it was a place that a lot of Navajos were able to hide so that they didn’t have to go on the Long Walk. But even now, today, there are still Navajos that live in that canyon.

And so, as soon as the science team realized that this canyon had that kind of significance, they took the steps to reach out to the Navajo Nation president. And at the same time, they reached out to me, and they asked if I wanted to be part of that conversation, and I was happy to. This would be an amazing opportunity to promote the Navajo language.

[32:16] The Navajo language is something that we’re always fighting to preserve. Fewer and fewer people are able to learn – even myself, I didn’t grow up speaking it fluently. So language preservation and revitalization is a big effort on the Navajo Nation. And so, we met with the Navajo Nation president, and after talking it through, decided that while Perseverance was in the Canyon de Chelly quadrant on Mars, they would name the science targets that they encountered in the Navajo language.

So a few of the names that we identified are things like “naa t’ anii,” which means “leader.” There’s another one like “nizhoni,” which means “beautiful.” There’s also some more descriptive things, like “tsé lichii,” which basically means “red rock.” Or “sisnaajini,” which means like “black mountain.” And there’s even some funnier ones, like we decided to assign a certain small bumpy rock “ch’ął,” which means “frog.” We decided to also use the word “shił łikan,” which means “delicious” in Navajo. And I thought that would be appropriate for our geologist friends, who sometimes, when they’re studying rocks, like to lick the rocks, so they might think it was delicious.

[33:29] So, it’s a long list. And to be honest, it happened so quickly, more than we could produce words, they were being assigned to things. It even got to the point where we were just creating numbers like, “Here’s how you count to 20 in Navajo.” And they were just like, “All right, we’re using them!” (laughs) So I don’t have a full comprehensive list of everything that was used, but it’s pretty incredible to see all these Navajo words pop up in mission reports. It’s just so amazing!


Narrator:Aaron says that learning the history of Mars aligns with Navajo storytelling traditions.

[34:14] Aaron Yazzie:As Navajo people, one of the biggest parts of our culture is all the stories that we tell that explain our origins: the ways that we as people came into this current world, how things like the stars in the sky developed and came to be and why they look the way they are, the way that animals came to inhabit the Earth. I think knowing where we came from and all of our origins, that story is very important to us.

And I’ve come to realize that my role here at JPL, studying Mars, helping us understand how our rocky terrestrial planet might have developed over billions of years, is essentially seeking answers to the same question. What are our origins? Where did we come from? How did we as humans end up on this Earth?

[35:06] Narrator: Aaron’s origin story at the Jet Propulsion Laboratory took a page from a chapter in his childhood.

Aaron Yazzie:I grew up in Holbrook, Arizona. It’s a small town in northern Arizona just off the border of the Navajo Nation. There’s a pretty large Navajo population there, but also equally non-Navajo population there. The place that my childhood home was built on started out as just a big empty lot of the desert, like sagebrush and sand. And we cleared it out, and my dad with me and my two brothers were always doing a lot of work outside. And I just remember always shoveling dirt all the time. And I remember thinking like, “Man, I can’t wait until I go to college and get a job that has nothing to do with shoveling dirt,” because I was so sick of it. (laughs)

And then you fast forward all the way to me getting one of my first tasks here at NASA-JPL. The little pocket that I found myself in is the Sample Acquisition and Handling Group, and we’re the group that gets to play in the dirt and figure out how we pick up samples from other planets and moons and asteroids. And we actually manufacture dirt or regolith that is similar to what we might encounter on Mars that has a certain ratio of rocks and sandstones and mudstones, and grind them up to a certain powder level, and then mix that up and then you get a Mars simulant.

[36:33] And so, one of the first things that I had to do as part of that team was to set up a scooping test which used Mars simulant, which basically meant that I was shoveling dirt into a giant sandbox so that we could use it for one of our tests.

(sound effect: shoveling dirt)

Narrator: Aaron doesn’t need to dig very deeply to connect with his family’s ties to the land.

Aaron Yazzie:My grandparents lived a very traditional Navajo lifestyle, which means that they basically lived off the grid. They lived in what are called “hogans,” traditional houses that Navajos lived in. It’s usually made out of logs, and it’s usually an octagon shape that gets built up into being a large-ish one-room home.

[37:16] And a lot of their livelihood was taken from the land and living off the land. They raised livestock. They had cornfields. They also grew squash and beans and watermelons and that kind of thing, but corn was the big crop that they usually would plant, and my grandparents were really good at it. There was no set calendar or anything, they just kind of knew by the seasons and the feelings.

(sound effects: soil running through fingers, wind)

Aaron Yazzie:I just remember my grandmother touching the ground and running it through her fingers, and sometimes even tasting it to see if the field was ready to plant.

And so, it was just a very strong connection, intimate connection, with the land and the environment around them. My grandma was sort of like the first scientist that I knew, because she was just so knowledgeable about all of that.


[38:10] Narrator: Those geologists who lick rocks might especially appreciate how the flavor of earth infuses some of the recipes his grandmother cooked.

Aaron Yazzie:There’s these types of traditional Navajo foods you can make with corn, like steamed corn. The way that we would do it is that usually you would build a giant mud hut, starting with rocks and then covering it with mud and making sure that there’s no leaks, no holes. And then you build a giant fire inside of that mud hut, and you let it reduce down to very hot coals. Then you throw a layer of corn husk on top of those coals, and then you dump as much corn as you can fit inside that hut as possible. And then you seal it up, with mud again, and then you check all over to make sure that there’s no steam escaping, that everything is very nicely, tightly kept inside of that hut. And you let it sit there for half a day or overnight, and then when you open it up, everything has been steamed to perfection. And it’s different from the steamed corn you might make on the stove. Somehow it just tastes more earthy, and it’s so delicious.

[39:14] Narrator: Aaron got his first taste of another kind of world – the world of science, technology, engineering and math – or STEM – through his parents.

Aaron Yazzie:My parents didn’t learn English until they went to school. Navajo was their first language. And my parents are the first from their families to go to college. So my dad became a civil engineer and my mom became a math teacher. And so I enter this world, and I already have parents who expect me to go to college. And so I took education very seriously. But I didn’t really have a clear direction.

So, when I was in high school, the summer after my freshman year, I went to the Upward Bound program that was hosted by Northern Arizona University, which is in Flagstaff. It’s the next big city over from my small town. And it was geared towards underrepresented students, and the theme of the summer program was to introduce us to different STEM topics. And it was the first time that I got to sort of be away from home for a period of time, live in a dorm with a bunch of other Native students that were like me, to do nerdy things over our summer. And that was a great time for me to realize that that’s something that I really liked and wanted to do.

[40:29] Narrator: Aaron went on to study engineering at Stanford University, but transitioning from his more familiar world to this intense academic realm wasn’t easy.

Aaron Yazzie:When I entered college, I was no longer in my small town public high school. I was surrounded by tons of brilliant people and it just seemed like academics were moving at a much higher pace than I was used to. I had to learn how to be a different kind of student, and sort of catch up to my peers in order to make it.

And on top of that, I had to use scholarship and financial aid to make it through. And if I were to mess up on any class, that could jeopardize me being able to pay for college, which meant that I might have to drop out. And so, there was a lot of pressure because of all of the financial stuff.

[41:17] And when I left home and entered my first engineering class at Stanford, I found myself as the only Native American in the room. And it continued to be that way through all of college and most of my NASA career. There isn’t a very high representation of Native Americans in the STEM fields. And so sometimes that can be a challenge; that can feel lonely to navigate this path, doing something that not many have done before you.


Narrator: The COVID-19 pandemic introduced a new level of loneliness and isolation, just as Aaron’s team was finishing their drill testing for the Perseverance rover.

[42:05] Aaron Yazzie:There’s still tons of work to be done, and we had to try to do that remotely. One thing that happened during the middle of the pandemic is that we still had to deliver another set of hardware that was supposed to be pristinely clean. And so, my team got to reunite with each other after being working remotely for two months or so. And we got to go into the clean room, where it’s actually a lot safer than it would be in the normal world. And so, we actually got to hug each other (laughs) and give each other a high five for the first time since the rover landed. So that was kind of a sweet moment for us.

Narrator: Now that Perseverance is drilling rocks and filling up its sample tubes, Aaron is helping develop a plan to send those Mars samples to Earth.

Aaron Yazzie:Perseverance, of course, is the first leg of the Mars Sample Return campaign. The next step is a lander, and I’m on the team working on the lander.


[42:58] Aaron Yazzie:So specifically, there’s a system called the “sample transfer system.” And it’s just basically the way that we transfer samples from Perseverance into this lander where we will pack them into a little canister that we’re going to launch into orbit around Mars. And then, a third mission is going to come and intercept that canister and bring all the samples back home. So my team is trying to figure out how we can safely grab our sample tubes from Perseverance and get them packed safely inside of that rocket.

Narrator: Beyond Mars Sample Return, there are other plans to dig even deeper into the mysteries of Mars. Here’s Brian Muirhead, a JPL engineer who dreams up ingenious solutions for far-future projects.

Brian Muirhead:I was working on a proposal to land a mission that could do deep drilling on Mars, because I think that’s part of where the real action will be in the future. You want to get deeper. You want to get down below the radiation levels and the thermal cycling and where maybe there’s moisture – hopefully there’s moisture and that things could be alive. They’re found in some really unusual places on Earth. Amazing that life survives and continues to live, you know, how many kilometers down in ice in the Antarctic?

[44:19] So this mission I was working on was looking at sites where it’s believed water is within a meter of the surface – not liquid water, but water in some state, ice or ice and regolith. But you know, the argument, I think, can be made that it was liquid at one time. One of the arguments is that, if it’s in the mid-latitudes, it heats up in the summer, and you could actually have ice transition into a liquid state. Life would have an easier time getting established and maintaining itself obviously in a liquid. That’s where it would really have to start, I think, but then it could survive in a frozen state.

So if you can drill a couple of meters down, now you can get into water-rich material that would be a good place to make measurements and possibly identify the potential for life to be there. And drilling on Mars has been something we’ve wanted to do for a long time, but deep drilling is a harder problem. But I think we’ve gotten to the point where we really know how to do that.

[45:22] Narrator: So far, the deepest rovers have drilled on Mars is 2.8 inches, or 7 centimeters. Rovers will need to dig at least 6.6 feet, or 2 meters to get below the sterilizing effects of surface radiation. The InSight mission showed us that digging deep on Mars will not be easy. That lander had a probe designed to hammer itself as far down as 16 feet, or 5 meters, but the probe only burrowed a few inches into the ground. The Martian sand didn’t provide the expected friction, and so the probe kept popping out of the hole it was trying to dig.

Another tough challenge comes from the surface rather than the depths. Fine-grained dust continually flows around Mars, seeking to swallow up missions. Solar panels can’t generate power when they become too thickly coated with dust, but even missions that don’t use solar power struggle as the tiny grains worm their way into gears and wheels and other mechanisms that can cause a rover to gradually stiffen with dust-induced arthritis.

[46:33] The problem of dust on Mars again has echoes from the Apollo missions to the Moon.

Apollo 17 astronaut Jack Schmitt: Well, everything’s getting awful dusty.Apollo 17 astronaut Gene Cernan: Boy, everything is stiff. Everything is just full of dust. There’s got to be a point where the dust just overtakes you, and everything mechanical quits moving.

Narrator: The fine dust on the Moon not only damaged their equipment, but also caused overheating, because the dusty coating prevented heat from radiating away. The gray dust made dials, gauges, and work checklists difficult to read. Despite the astronauts’ constant brushing, the electrostatically-charged moondust clung tenaciously, and affected their lunar experiments. The dust also clogged zippers and seals where helmets and gloves attached to the spacesuits. Anything sticky, like duct tape, was soon rendered useless.

[47:24] Apollo 12 astronaut Alan Bean: Houston, I’m not kidding. We are really getting dirty out here. There’s no way to handle all this equipment with all the dust on it. Every time you move something, the dust flies; and, in this low gravity, it really takes off. Goes way up in the air and then comes down and lands on you.

Narrator: Before the Apollo 12 astronauts launched off the surface of the Moon to rejoin the Command Module that was orbiting above, Pete Conrad noted that they, and the cabin of their Lunar Module, were very dirty.

Apollo 12 astronaut Pete Conrad: We’ve got the spacecraft all squared away. I’ll say everything’s tied down, but man, oh man, is it filthy in here; we must have 20 pounds of dust, dirt, and all kinds of junk.Mission Control (Ed Gibson): Roger, Pete. That’ll be an interesting zero G.Pete Conrad: Right. Al and I look just like a couple of bituminous coal miners right at the moment.

[48:23] Narrator: Once they left the Moon, dust that had drifted to the floor thanks to lunar gravity was soon floating around the cabin. The sooty dust so irritated their eyes the astronauts had to keep their helmets on until the air filters could scrub out most of the haze. When they docked with the Command Module, the pilot Dick Gordon declared that they were too dirty to come into his spacecraft, and so he had them strip down, leave everything behind in the Lunar Module, and float inside wearing only their headsets.

After they took off their gloves, the astronauts’ hands quickly became black with moondust, and the dust stayed embedded in their fingernails for weeks after their return to Earth. When they inhaled the dust, they discovered it had a distinctive smell.

Apollo 16 astronaut Charlie Duke: Houston, the lunar dust smells like gunpowder.Mission Control (Tony England):We copy that, Charlie.Charlie Duke: Really, really a strong odor to it.

[49:24] Narrator: Breathing in the dust created an allergic reaction for at least one astronaut, Apollo 17’s Jack Schmidt.

Mission Control (Joe Allen): Sounds like you’ve got hay fever sensors, as far as that dust goes.Apollo 17 astronaut Jack Schmitt: It’s come on pretty fast just since I came back. I think as soon as the cabin filters most of this out that’s in the air, I’ll be all right. But I didn’t know I had lunar dust hay fever.

Narrator: Moondust is the result of billions of years of meteorites pummeling the lunar surface. Without any wind or water to smooth them down, the microscopic shards of volcanic dust stay just as sharp-edged as when they first formed. So this gritty dust scratched the glass of the astronauts’ helmets, creating a sightless glare whenever they faced the Sun. The dust also caused notable wear and tear on their spacesuits after just a few hours, far worse than what was seen in the training suits the astronauts had worn for hundreds of hours prior to their trip to the Moon.

[50:36] Apollo 16 astronaut John Young: Houston, this dust is just like an abrasive. Any time you rub something, you can no longer read it. And that’s what’s happened to our RCUs and our… and our uh… (laughs) every piece of gear we’ve got. In other words, it’s a mistake to rub something to clean it off.Mission Control (Tony England): Understand.John Young: Big mistake.

Narrator:The dust on Mars may not be as abrasive as moondust, because Mars has wind to help sand down rough edges over time. But that wind also presents a danger to electronics, since dust storms and dust devils on Mars may develop electrical fields, similar to thunderstorms on Earth, that generate lightning.

[51:24] Until the samples collected by Perseverance are brought to Earth, we won’t know every facet of Mars dust, but future Mars astronauts will want to stay clean of it. To prepare for this human exploration, Perseverance holds spacesuit materials, like vectran and teflon, to see how well they hold up against the dust over the years, as well as other aspects of the Martian environment like big temperature swings and intense UV radiation.


Narrator:In time, all Mars rovers become thickly coated with dust, becoming one with the planet they came to explore.

[52:04] Aaron Yazzie:That kind of dry powder is more susceptible to get everywhere (laughs) and to get into the mechanisms and stuff. And it wants to stick to surfaces – if there’s a static buildup, that powder will want to cling to those surfaces. So, making sure that fine sand doesn’t make its way into the gears – you can imagine, it just sort of starts to act like sandpaper, like it starts to grind a little bit at a time, starts to seize up gears, it starts to wear away different surfaces, so everything will just become less efficient.

So we strategically assemble all the mechanisms to protect the really highly sensitive ones, and nest things inside of each other. They call it “creating a tortuous path,” making sure that a dust particle has to travel this crazy maze to get to the mechanism. And then we have a bunch of little tiny seals that help to keep all of that sand and dust out.

[53:04] But we know that over time, those seals will get a little bit weaker and they might let in more dust. So it’s all a matter of time that we’re trying to make sure that we minimize the amount that can get in there so that we can have our mechanisms last longer.


Narrator: We’re “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory. If you liked this episode, please follow and rate us on your favorite podcast platform, and be sure to check out NASA’s other podcasts: they can all be found at NASA dot gov, forward slash, podcasts.

(Episode length = 53:47 min)