Last fall, NASA announced that it found something incredible in a rock on Mars. A core sample obtained by the Mars Perseverance rover discovered a potential biosignature. In other words, a potential sign of ancient life on Mars. Dean Regas chats with Kathryn Stack Morgan, Perseverance project scientist at the Jet Propulsion Laboratory, about this chemical "fingerprint."
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Dean Regas: Five years ago, a new rover landed on the surface of the planet Mars, about 20 meters off the surface.
[Perseverance Rover’s Descent and Touchdown on Mars]: "We're getting signals from MRO Tango Delta. Touchdown confirmed. Perseverance safely on the surface of Mars, ready to begin seeking the signs of past life."
Dean Regas: The Perseverance rover survived its seven-month, 292-million-mile journey from Earth to the Red Planet. It was so far from Earth that NASA engineers couldn't manually guide the craft gently down to the surface. It all had to function perfectly and autonomously over the course of seven minutes. Seven months in space comes down to seven minutes of terror. What? At work? Oh, yeah. No problem.
From the studios of Cincinnati Public Radio, I'm your host, Dean Regas, and this is Looking Up — the show that takes you deep into the cosmos, or just to the telescope in your backyard, to learn more about what makes this amazing universe of ours so great.
My guest today is Kathryn Stack Morgan, Perseverance project scientist at the Jet Propulsion Laboratory.
Last time on Looking Up, we spoke with Dr. Andy Czaja about the seven minutes of terror — you know, the Mars rover landing procedure and then what they call the seven minutes of terror at the end when the spacecraft reaches the top of the atmosphere, and then everything has to happen in order.
And we also covered a variety of intriguing water features on Mars: the dried-up river valleys, ancient lakes and seas. Mars seems to have had a lot of water in its past.
Where I live in Cincinnati, Ohio, we have some incredible rocks, too — in every creek and every cut in the hill. If you pick up a rock, chances are you'll find ancient signs of life. There's fossils everywhere. 450 million years ago, the Cincinnati region was underwater. A shallow sea covered the area where sea creatures thrived.
It's so hard to picture 450 million years ago. Imagine trying to piece together what was going on on another planet billions of years ago. What would you look for? Are there signs of life on Mars? And what would they look like?
Dr. Katie Stack Morgan: Hi, my name is Katie Stack Morgan. I am the project scientist for the Mars 2020 Perseverance Mars Rover, and I'm in charge of leading a science team of over 400 scientists from around the world operating the Perseverance rover on Mars.
Dean Regas: Well, Katie, thanks so much for joining me today.
Dr. Katie Stack Morgan: Glad to be here.
Dean Regas: So last fall, NASA announced that it found something incredible in a rock on Mars. It's from a core sample obtained by the Mars Perseverance rover. What was on that rock?
Dr. Katie Stack Morgan: Yes. So we discovered with Perseverance what we consider a potential biosignature. And so that is a potential sign of ancient life on Mars.
Dean Regas: Well, and what do these biosignatures look like?
Dr. Katie Stack Morgan: Yeah. So we informally call these potential biosignatures leopard spots because they look exactly like the spots on a leopard. They have a dark rim and a lighter center, and they're set in a rock that's kind of reddish in color. So when you look at it, the first thing you think is leopard spots. So that's what we call them. But of course, they're not at all related to the animal on Earth.
Dean Regas: OK, so let me put words in your mouth. You're saying that is definitely life?
Dr. Katie Stack Morgan: No, not definitely life. The potential is doing a lot of work here, and that's a really important word. We define potential biosignature as a feature or texture or composition or pattern that we find that may have been formed by life, but that we need further analysis or information about to confirm the presence of life. But as you wouldn't be surprised to know, scientists have lots of different levels of terminology. And so we bring out potential biosignature for something that we think is really compelling, and that for which life or biological origin may be the best explanation, though we can't say for sure yet that life formed these features.
Dean Regas: Well, I'm trying to think of, like, what are some examples of similar biosignatures on Earth that you might find?
Dr. Katie Stack Morgan: One of the best examples of a biosignature on Earth in ancient rocks — which is what we're working with on Mars, so it's helpful to go back to the early Earth record and look at examples there — but one example of a biosignature is something called a stromatolite, which is a fossilized microbial mat.
And so, you know, many hundreds of millions of years ago, you had kind of a sticky layer of microbes, and then sediment falls on top of them, little sand grains. And then those microbes say, oh, but I got to get closer to the sun. So they kind of grow a new little layer, and then more sand piles on top. And so over time, they create this layered sandwich of mat, sand, mat, sand. And these microbial mats can form in all kinds of interesting, weird structures and textures.
And so when we see them in rocks today, we look at them and say, hmm, that doesn't look like a kind of process or texture that would form without the presence of life, because those sticky microbes are doing a lot of work to create these weird textures. And so that's an example. That's a very visual example of something where we look at it and we say, hmm, can you explain this with physics? Probably not. And so that's where we start to think about the role of microbes.
Now, we haven't found a stromatolite on Mars, but we've found a chemical fingerprint that could have been left behind by ancient Martian microbes. And of course, the first question we ask is, well, could you form these leopard spots without life? And the answer is yes, you can form these without life. But there are certain conditions — temperature, pressure — in which these are really hard to form without life being there. And what we think is that those conditions that we have in the Martian rocks made it less likely for these kinds of things to form if life wasn't there. So that's why we're so compelled by the possibility that these leopard spots were formed by life.
Dean Regas: Well, it's a little hard to picture the environment and where the Perseverance rover is rolling. You know, it's in this old crater, but it did have this watery past. Describe what it might have looked like back in the day when water was there.
Dr. Katie Stack Morgan: Yes. OK. So you can picture a big bowl, big crater, and there's a rushing river cutting through the crater wall and depositing sediment and water inside the crater. And in this river channel that cuts through the crater wall and brings the water and sediment into the crater there, we're basically on the side of this river channel. And at some point, this river channel might have gotten a little backed up.
Maybe there's a lot of sediment flowing in and it sort of cut off the flow a little bit. Either way, we think a small lake might have formed in this channel, and that means that the water was just kind of sitting there, not rushing and flowing particularly quickly. And so we're in this river channel. There's probably standing water in this river channel. And so we've got water, we've got sediment — fine-grained sediment falling out of the water, depositing on the floor of this river channel. And within this, we have a chemical reaction taking place in the sediment. And so the water is nearby and maybe infiltrating into the sediment.
And then we have this chemical reaction happening between organic molecules that are present in the sediment, iron — the element iron — present in the sediment, too, and then the water that's there. And you have this recipe of water plus the iron plus the organics. And these are forming these leopard spots. Now the question is, was life an important ingredient in this recipe or not? And here on Earth, these kinds of features form with life as an important ingredient. And so the question is, were they there on Mars, too?
Dean Regas: And the rock — or the sample — it's safely stowed within the rover. Is that correct?
Dr. Katie Stack Morgan: Yes. That's right. So Perseverance has the ability to collect kind of pencil-sized rock cores. And so we collected a sample of this rock that has the leopard spots. And we could even see the little tiny leopard spots when we took a picture of the top of the core, and we were able to seal this tube up. So it's nicely preserved, very safe inside the body of the rover, and it's ready to be dropped on the surface of Mars or handed off to a follow-on mission — if that ever comes — to pick up the samples.
Dean Regas: So is it ready to be picked up? Or is there a plan for future missions to try to get that?
Dr. Katie Stack Morgan: So there has been a lot of planning and a lot of discussion about Mars Sample Return and the process and architecture for getting Perseverance's samples back to Earth. And that's of course our ultimate goal here. But like many Mars mission concepts, it is going through a roller coaster of ups and downs. And Mars Sample Return is something that folks have wanted to do for decades, and Perseverance was identified as the first step in this process. And so the rover's done its job of collecting and preserving a compelling set of scientific samples for return.
And so now the question is, can we get them home? And there have been plans to send follow-on missions. Given the current and recent discussions at NASA and budgets that have been put out, it's not clear what the future of that plan is, but we are still hopeful on the Perseverance rover team that these samples are coming home, and we're going to carry on the great work of filling up the sample tubes. We have a couple more still to go. So we're going to keep putting fantastic rocks in those samples and hope that NASA formulates a plan to bring them home.
Dean Regas: So if you had that Mars rock sample here on Earth, what would you like to do to it? Like, how would you study it in person and what would you look for that you can't do remotely?
Dr. Katie Stack Morgan: The first thing would be to make a thin section out of it. So that's where you take the rock — you could just bring a chunk of the rock in from the field, or in this case, from the sample tube — slice it really thinly and then look at it under a microscope. And when you do that, you can see all different kinds of textures and relationships in the components of the rocks that you can't see just by looking at it.
And so I think that would be step one, to just see this rock at the fine scale, to better understand the relationship between these leopard spots, the minerals that make it up, the sediment that forms the rock. And then we would get to the fun things, which I think are taking advantage of all of the analytical advancements we have here on Earth. And I think what we've learned over the past, let's say, 50 to 60 years, is the value of isotope analysis. Life tends to leave isotopic fingerprints behind. Isotopes are one of the ways that we identify potential biosignatures in rocks, in early Earth rocks. Those would be some of the first things that I'd be interested to see, and I can't wait to see the first SEM image of the leopard spots when that sample comes back home.
Dean Regas: Was there anything about the discovery that surprised you?
Dr. Katie Stack Morgan: Hmm. Well, I think the whole thing was kind of surprising, honestly, because this outcrop where we found the leopard spots was on our radar for years. I mean, we knew this was going to be an interesting outcrop, but not necessarily for the reasons it turned out to be.
This outcrop was right there at the entrance of the crater, and there was a question of whether these rocks were going to be really young rocks deposited in the channel at a very late stage, or whether we were actually looking at a block of the ancient Martian crust that was uplifted and now exposed by this river channel. And so we had picked this outcrop out a long time ago and said, we want to send the rover here, but we didn't know what we were going to find there.
And so when we drove up to it and we saw that it looked like sedimentary rocks, I was like, OK, this is cool. I like sedimentary rocks. This is for me. But then we didn't expect to see these interesting features inside the rocks. And I have worked 13 years on Mars rover missions — first with Curiosity, now with Perseverance — and I've never seen something quite like this. And when you've looked at a lot of images on Mars, when you see something unusual, you kind of know it's like, oh, that's different. And I remember seeing this image that we got from this rock, and I thought, whoa, that's something special. Anyway, that was unexpected. I wasn't expecting those leopard spots to be there. Never seen anything quite like it on Mars or in Mars rocks before. And so that was pretty exciting.
Dean Regas: Well, I'm sure you've come across a lot of people that have been a little hopeful — those aliens — and maybe misunderstood this idea, but what would you want the general public to take away from this mission and this discovery?
Dr. Katie Stack Morgan: Yeah. I mean, we have a lot of optimism about the potential for life on Mars. The conditions were there, all the ingredients were there. It's just a matter of whether we can find it and whether we have the right instruments to really confirm that. And I think with Perseverance, we are in the right place. We have the right rock. We just have to seal the deal. So we are so close to answering the question of whether we've discovered life on Mars. I mean, this is such a fundamental question we've asked for so long, and we're so close to the finish line — and it's not even the finish line. It's really the start line. I mean, if this sample has life, it's a whole different game or race we're playing here, right? If we can just get this rock home, confirm or deny — incredibly important discovery. Perhaps one of the most important discoveries humankind could ever make.
Dean Regas: Katie, thanks so much for joining us today. This was a lot of fun learning a little bit about Mars, and fingers crossed — let's get that rock back.
Dr. Katie Stack Morgan: Thanks for having me.
Dean Regas: Hearing about the rover searching for signs of life on Mars really got me thinking. What is it like to be a Mars rover driver? Come on, don't you want to know, too? I was really good at those old arcade driving games, but those skills and my general impatience for commuting to the Looking Up studios would not help me at all.
Mars is so far that light — as well as radio signals — takes four minutes to get there. That's when Mars is closest to us. At its farthest, Mars is 24 light-minutes away. That means to drive a rover on Mars from Earth, you have to think ahead and be extremely cautious. Imagine playing Mario Kart with, like, a 20-minute lag.
Here's an example. The rover camera shows you an interesting rock ahead on Mars. Let's drive in for a closer look. You order the rover to roll forward 10 feet. Send — 10 minutes for the signal to get there. Ten more minutes for the rover to send back confirmation of the move. Oops. We needed to turn more to the left. Another signal. Another wait. Still too far for the drill to reach it. Adjust. Wait. Adjust. Wait. Don't go too fast. Don't hit a rock. Don't tumble over.
You're limited by daylight, too. I mean, you can't drive in the dark. Daytime on Mars is similar to Earth. One day lasts about 24 hours and 40 minutes, and factor in the season — yes, Mars has seasons like Earth — you might only get to see one rock up close on a given day. If you're lucky, you'll find something cool. If not, next rock, next week.
Do you think you could do it? Drive a rover? Let us know. Leave us a voicemail at 513-352-9188, and you might hear yourself on a future episode.
Hmm. Do I still want to be a rover driver? I definitely have the curiosity, but probably not the perseverance.
Looking Up with Dean Regas is a production of Cincinnati Public Radio. Kevin Reynolds and I created the podcast in 2017. Ella Rowen and Carlos Lopez Cornu produce and edit our show and possess both curiosity and perseverance, as well as spirit and opportunity. Jenell Walton is our vice president of content, and Ronniy Salerno is our digital platforms manager. Our theme song is "Possible Light" by Ziv Moran. Our social media coordinator is Hannah Pflum, and our cover art is by Nicole Tiffany. I'm Dean Regas. Keep looking up.
