What was the planet Mars like in the past? Was it a dry desolate world like the one we see today, or was it a watery oasis filled with oceans, lakes, and rushing rivers? Was it Earthlike? Dean Regas chats with University of Cincinnati Professor of Geosciences, and NASA Advisory Board Member, Dr. Andy Czaja, to find out more.
We want to hear from you!
Leave us a voicemail by calling (513) 352-9188 and you might hear yourself in a future episode!
You can also send us your thoughts on this episode at lookingup@wvxu.org or post them on social media using #lookinguppodcast
Episode Transcript:
Looking Up is transcribed using a combination of AI speech recognition and human editors. It may contain errors. Please check the corresponding audio before quoting in print. This transcript may include additional material from the conversation, not featured in the audio.
Dean Regas: What was the planet Mars like in the past? I'm talking way, way, way back millions of years ago. 1 billion years ago. Was it a dry, desolate world like the one we see today?
“Men Encounter Mars” (1965): Picture No. 11 shows craters 3 to 75 miles across and several thousand feet deep. The picture suggests that Mars has never had an ocean or substantial atmosphere.
Dean Regas: Or was it a watery oasis filled with oceans, lakes, and rushing rivers?
“NASA’s Curiosity Rover Finds Old Streambed on Mars.” (2012): These gravels that we're seeing here are one, the rounded shape, but also, the size. These are too large to be transported by wind. The consensus of the science team is that these are water-transported gravels in a vigorous stream.
Dean Regas: Was it, dare I say, Earth-like?
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 Dr. Andrew Czaja, University of Cincinnati professor of geosciences and NASA advisory board member.
NBC News. “New NASA Findings Move Closer to Uncovering Mars’ Mysteries.” (2022): NASA today, moving ever closer to unlocking the mystery of Mars. These already are the most valuable rock samples that have ever been collected.
Every day we're watching, studying and probing the planet. Mars orbiting spacecraft observe every square foot of the planet from above, while two rovers roll on the Martian surface. What are they seeing?
ABC News. “Rock Found on Mars Could Be Evidence of Ancient Life, NASA Says.” (2025): A year ago, we thought we found what we believed to be signs of microbial life on the Mars surface.
What can it tell us about what Mars was like before? When you look at images of Mars from above, it sure looks like a desolate wasteland brown, orange and rusty red rocks, mountains, valleys, long-dormant volcanoes, ancient craters from impacting asteroids. But no water. At least no flowing water.
The atmosphere on Mars is so, thin that water cannot exist long in liquid form. If you spilled a glass of water, it would either freeze or poof, turn into a gas and go into the atmosphere. But there are signs that Mars hasn't always been so, waterless. We know there's frozen water trapped in the north and south poles. That's the whitish stuff you see at the top and bottom of the planet. And the orbiters have noticed places on the planet where the Martian soil is eroding, as if water is flowing under it.
MSNBCW. “Chris Jansing Reports” (2025): Scientists reveal they found water on Mars enough to fill oceans buried several miles below the surface.
And a Mars lander called Phoenix dug its robotic arm into the Martian soil, scooped out a little hole in the ground, and what formed in the hole water ice. There's probably a ton of water just below the surface. Well, much more than a ton.
MSNBCW. “Chris Jansing Reports” (2025): Enough to fill oceans.
Not to mention the features on Mars that sure look to me like curvy, snaky riverbeds. All signs are pointing to a watery past on Mars. But what's it like if we drive a rover up one of these ancient rivers? And can a rover currently on Mars confirm our suspicions?
Dr. Andy Czaja: Hi, I'm Andy and I'm a professor of geosciences at the University of Cincinnati.
Dean Regas: Well, Andy, thanks so much for joining me today.
Dr. Andy Czaja: Oh, glad to be here.
Dean Regas: So, the Perseverance rover it's been on Mars for more than four years now. Tell me about the journey it took from launch on Earth to a safe, soft landing on the Martian surface.
Dr. Andy Czaja: Yeah, it launched in July of 2020, and it took about seven months to get there because it's quite a long ways from here to Mars. The actual distance really depends on where we are in the solar system as we orbit the sun. About the shortest time it can take is about seven months. So, it launched, everything went perfect, it cruised for a whole bunch of months. And then it comes down to 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.
Scientific American. “Experience Seven Minutes of Terror Strapped to the Perseverance Mars Rover.” (2021): We are starting to straighten up and fly right, maneuver the parachute, deploying the heat shield, dropping away. The navigation has confirmed that the parachute has deployed, and we are seeing significant deceleration.
Dr. Andy Czaja: It had something called terrain relative navigation. So, it had an AI system in it that could identify features in the region that we wanted it most to land. And it could then steer itself a little bit all autonomously.
Scientific American. “Experience Seven Minutes of Terror Strapped to the Perseverance Mars Rover.” (2021): We have completed our terrain relative navigation. Current speed is about 30 meters per second, altitude of about 300 meters off the surface of Mars.
Dr. Andy Czaja: And then found the place it wanted to land and deployed the sky crane, which lowered it slowly to the ground.
Scientific American. “Experience Seven Minutes of Terror Strapped to the Perseverance Mars Rover.” (2021): Sky crane maneuver has started about 20 meters off the surface,
Dr. Andy Czaja: And everything went exactly as the engineers planned, as far as I know.
Scientific American. “Experience Seven Minutes of Terror Strapped to the Perseverance Mars Rover.” (2021): Touchdown confirmed. Perseverance safely on the surface of Mars, ready to begin seeking the signs of past life.
Dr. Andy Czaja: Yeah, it was quite the journey.
Dean Regas: And then, so, the landing site ended up being this place called Jezero Crater. It's a large impact crater with some fascinating features. So, why was this site chosen?
Dr. Andy Czaja: Yeah. So, one of the overall goals and objectives of this mission is to search for evidence of ancient life on Mars. So, to do that, you want to find a place where it's possible that if there was ever life on Mars, that it would have lived there, and also that it could get preserved. And a great place for that is a body of water. Right on Earth, if we're looking for fossils, we look in places that used to be underwater. It's very difficult for things to get preserved on top of a mountain. But down in a lake or in an ocean, things can get buried under sediment, under broken-up bits of rock that get washed downstream. And Jezero Crater is one such place. Jezero Crater, as you said, formed as an impact almost 4 billion years ago on Mars. But after that, it got filled in with water. There's lots of evidence that water flowed from the higher area surrounding it and flowed in through an inlet channel. It breached the edge of the crater and filled it up as a lake at one point in the past. A lake is a great place for life to survive and live, but also, a great place for it to get preserved.
Dean Regas: Yeah, I mean, those images from those orbiting spacecraft you can see this looks like a dried-up riverbed snaking around here. And then where it enters into the crater, it sure looks like a river delta. And, you know, it looks like the bottom of the Mississippi River going to the Gulf of Mexico. So, what did the Perseverance rover find there?
Dr. Andy Czaja: Yeah. So, where we landed, we were out on what's called the crater floor. And the majority of it seems to be filled in later. It's not the bottom of the crater right after the crater formed stuff filled it in and we weren't sure if it was going to be sediments, you know, stuff washed in by wind or water, or if it was going to be emplaced some other way by a lava flow or something like that. Well, it turns out that the crater floor likely is actually what we call an igneous rock, so, emplaced by liquid rock, having filled it in somehow. We're still not 100 percent sure how that happened, but the rocks seem to be that way. But on top of that, we do have the sedimentary rocks of the delta, and the sedimentologists the people on the mission who study rocks that form by flowing water based on analogy to rocks on Earth, they can look at it and say like, yes, we can tell that how these rocks are layered, how the shapes of the rocks, the shapes of the layers, the angles between them tells us that, yes, in fact, this was deposited underwater. So, the sediments came down river, just like the Mississippi dumping into the Gulf of Mexico, just like the Nile dumping into the eastern Mediterranean. You get sediment piling out into that water and it builds up in a certain way, transporting stuff downstream. And it flowed out and then just was deposited onto land.
Dean Regas: Yeah. So, I think we're all a little surprised and maybe a little bit cautious to read that headline from a little while ago that NASA's Perseverance Mars rover finds possible signs of ancient Red Planet life. I don't know, I've heard way too many signs of life stories on Mars to get too excited. But what did the Perseverance rover actually find and how excited should we be?
Dr. Andy Czaja: Yeah, so, you're right to be cautious when you hear anything about finding signs of life outside of Earth, because it's a hard thing to do. It's a hard thing to determine. To figure out what the Perseverance rover team found on Mars was in this one location there was, in the rocks that were deposited by water, water flowed in and deposited these very fine-grained rocks. So, right there, that's a place where life as we know it can live. And it's also a place where stuff can get preserved in those rocks. We found organic carbon, and organic carbon means the carbon that biology on Earth is made out of. And we think is probably what life in lots of places, including Mars, could be made out of again, if it exists. So, that alone, not enough evidence to say, hey, we found life. It's just consistent with life. We cannot claim that we found life on Mars yet, but it's intriguing. And the cool thing with the Perseverance rover is that one of the main things it's there to do is collect samples on board. Perseverance right now has a sample of those rocks that have those potential possible biosignatures in them.
Dean Regas: Well, Andy, I gotta say, that doesn't make a very good headline. You know, it's more realistic, but I guess you're probably right. Well, I want to go back to Mars's watery past. If he could take us back to its heyday Mars had water on its surface in abundance. What would it have been like if we visited back then? I mean, you know, at that point, did Mars have an atmosphere? And how much water are we talking and how long did it last?
Dr. Andy Czaja: Yeah. These are all excellent questions that as far as I know, no one has a strong handle on yet. There is lots of evidence that there was water on the surface of Mars. I already mentioned Jezero. There's evidence that it was full of water. How long? We're not quite sure. There's also large river systems that take a long time you know, possibly tens of thousands of years to develop. They don't happen overnight. So, there's lots of evidence that there was water and a significant amount of water on the surface, but it's still uncertain exactly how long it persisted. There may have been water falling on the surface at various times, and then it cooled off again and everything froze. And then things warmed up again later. But if you had liquid water, rivers and lakes, you had to have a much thicker atmosphere. So, we don't know exactly how thick. It's hard to constrain that, but we know Mars used to have must have had an atmosphere, whether it was, again, warm like Earth or if it was periodically warm, but also, very, very cold in between those somewhat warmer periods, is still an open question. And that's one of the reasons we're there, too, is to study the geologic past of Mars and collect samples that could answer some of those questions as well.
Dean Regas: Well, and your background is mainly geology and biology. How did you branch out to the Red Planet Mars and become a preeminent Martian hunter, too?
Dr. Andy Czaja: Well, I've always been interested in space, so, I study the earliest life on Earth as far back as we can go in our rock record, and we can actually use that as an analogue for an alien planet because the early Earth was very different than Earth is today. There was essentially no oxygen in the atmosphere. We still had a thick atmosphere, but it was nitrogen and probably a lot more carbon dioxide than we have now and some other gases. But, you know, there was no oxygen. And so, it was a very different planet. All we had was microorganisms. There was no plants, there was no animals. I'm talking more than 2.5 billion years ago, that is the time period I study. But I'm also, interested in how we can apply the skills that we can acquire by studying that time period to looking for evidence of life on another planet, because we have to look in rocks for evidence of this ancient Earth life. We have to look in rocks on Mars, too. So, the reason I'm on the Perseverance mission is I was selected as somebody who had that experience of looking for life in the rocks on the ancient Earth. I could help guide the mission, along with a whole lot of other people, on what evidence to look for while we're there on the planet, and what samples we should select that we could put in tubes again to be brought back by a later mission. So, I'm what's called a returned sample scientist on the mission. That's my official title.
Dean Regas: Well, I mean, you're here in Cincinnati, one of the most fossil-rich places around. And everywhere you go, you turn a rock over, you're going to find a fossil.
Dr. Andy Czaja: Oh, yeah.
Dean Regas: So, you've got to give me the scoop here. Is NASA expecting at any moment for the rover to, like, round a bend or kick up a rock, and on the bottom of that rock to find an actual fossil? Are they thinking about this, or are they like, is it even a possibility? Or are they even entertaining this? Or am I just going off on a tangent here?
Dr. Andy Czaja: Well, I wouldn't expect to turn a corner and, you know, knock over a rock and find, you know, a brachiopod or the sorts of shells we find around here in Cincinnati all the time. That sort of life, even though it's 450 million years old on Earth, that's about a tenth of the history the tenth of the age of the Earth. The Earth's 4.5 billion years old. And the time period we're looking at on Mars is comparable to that ancient Earth. We're talking 3.5 billion, 4 billion years ago on Mars. So, if we do find evidence of life, we would expect it to be microbial we expect it to be, and by that, I mean microscopic. So, you're not going to find an individual fossil by looking at the bottom side of a rock unless you have a really high-powered microscope to do so. But microbes sometimes do make larger structures, right? You can see a microbial mat growing on the side of a river or the side of a lake. You see this green, goopy, layered structure. If you cut down into it, you might see some layers. Those can get preserved in the rock record, too. That's one of the things I look for on the early Earth to look for evidence of life so, we could potentially find something that looked like that, and that would be very exciting.
Dean Regas: Well, Andy, thanks so much for chatting today. And you've got to promise that when you find a fossil, you let us know first.
Dr. Andy Czaja: Oh, sure. Sure, we'll do. Finding evidence of life on Mars is probably going to require bringing these samples back. There are 30 samples collected. Most of those are on board the rover. And we just need to, you know, we need to get those back.
Dean Regas: Talking to Andy about Perseverance reminded me of a watch party I went to in Tucson, Arizona. It was 2012 and a different Mars rover Curiosity was landing.
Curiosity Landing (2012): Sequels reporting heartbeat tones again, indicating that everything is fine during heading alignments. We are standing by for straighten up and fly right.
Dean Regas: The party was part of a conference for the Astronomical Society of the Pacific, and a bunch of us were in a hotel room watching the live feed from NASA. But I gotta admit, I wasn't watching the lander or even watching a live feed from Mars itself. I was watching the scientists and engineers reacting to information coming from the rover millions of miles away.
Curiosity Landing (2012): Parachute deploy. Parachute.
Dean Regas: I remember these engineers' faces, their anxiety.
Curiosity Landing (2012): We are decelerating.
Dean Regas: And then someone somehow, I don't know on their computer screen got info that the landing was done. The rover was safely down. Everything was a go.
Curiosity Landing (2012): Touchdown confirmed.
Dean Regas: And the place erupted. It was so moving. I mean, I was moved by their emotion. I mean, just watching all those nerds celebrate. I mean, they failed so badly to give each other high fives. I remember that so, much. But boy, could they land something on Mars.
I want to know more about what we're finding on Mars. Do you, too? Because next time on Looking Up, we're going back to the Red Planet and finding out more about signs of life not life itself, mind you. Or is it?
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 playfully call my intros "seven minutes of terror." Oh, come on, they only last like 45 seconds, tops.
Jenell Walton is our Vice President of Content, and Ronny 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!
