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Mars is cold & dry today, but the evidence is growing that it used to be warmer & wetter. with seas & oceans that covered large parts of its surface. With the additional findings of the chemicals for life, the search for life on Mars is getting pretty interesting! New results from Perseverance and Curiosity describe a past Mars with complex chemistry and water. But did it have life?

Show Notes

• The search for life on Mars
• Viking mission and its lasting impact on Mars exploration
• Evidence that Mars was once warmer, wetter, and potentially habitable
• Discovery of ancient rivers, lakes, shorelines, and possible oceans
• Confirmation of water ice by the Phoenix mission
• Curiosity rover's detection of organic molecules
• Perseverance rover's search for biosignatures and ancient habitability
• Bright Angel Formation and promising organic discoveries
• InSight's contributions to understanding Mars' interior
• Growing evidence for long-lived liquid water on Mars
• Why Mars Sample Return is essential for confirming past life
• Perseverance's cached samples and retrieval plans
• The delayed Rosalind Franklin rover mission
• Tianwen discoveries of ancient Martian shorelines
• Sample return missions as the next revolution in planetary science
• Could Mars preserve evidence of ancient microbial life?
• Future prospects for robotic and human exploration of Mars

Transcript

Fraser Cain: 

It's the 365 Days of Astronomy podcast, coming in 3, 2, 1. Astronomy Cast, Episode 796, Oceans and Organics on Mars. Welcome to Astronomy Cast, our weekly, facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know.

I'm Fraser Cain, I'm the publisher of Universe Today. With me as always is Dr. Pamela Gay, Senior Scientist for the Planetary Science Institute and the Director of Cosmic West. Hey Pamela, how you doing?

Dr. Pamela Gay: 

I am experiencing levels of spring that are unlike your levels of spring, but my weeds are taller than I am in some of my flower beds. Oh my goodness, things are growing like never before. And you have them trying to breed in your nose, from what I understand.

Fraser Cain: 

Yeah, so I returned from a trip in Japan to a wall of histamines. You know, all of the plant matter had been waiting for me to return. And so it's literally the moment I got off the plane in our home city, the allergies came roaring in.

And I am a Claretonian, and still, I know you can probably hear a little gloopiness in my voice. So I will do the best that I can to minimize it, and you know, our editors will clean up the dad sounds. But yeah, man, it is gorgeous.

You leave your garden for two weeks, you come back, and it has been busy and it's surprising and it's wonderful to see all of the changes. And no deer got in, which is great. So I get to see what trees look like when they're actually allowed to grow as opposed to savaged by brutal, cruel deer.

Dr. Pamela Gay: 

I have one hilarious green bean plant. They're growing up strings. And I have cages around the bottom.

And then the cage only goes up so high. And there is this naked section on the vines that is the part the groundhog could reach over the cage. So leaf, leaf, leaf, naked, leaves.

It's glorious and excellent. And the groundhog survived getting picked up by my dog and carried off.

Fraser Cain: 

Yeah. If you don't garden, why not?

Dr. Pamela Gay: 

It's the best.

Fraser Cain: 

Yeah. Yeah. Obviously, you know, some people don't have a room to garden, but even if you have like a little balcony, get gardening.

All right. Mars is cold and dry today, but the evidence is growing that it used to be warmer and wetter with seas and oceans that covered large parts of its surface. With the additional findings of the chemicals for life, the search for life on Mars is getting pretty interesting.

All right. So I want to talk first about like setting the scene, which was the dead end that the Viking mission got us to in the search for life on Mars. Can you tell this story?

Dr. Pamela Gay: 

So the Viking mission had three different experiments on board that were designed to try and identify, is there life here? Both by looking to see what chemicals were getting metabolized, how the air in the container was getting metabolized, and by looking at the organics. And they realized that one of the experiments, they had not taken into consideration the reality of Mars, and it was utterly inconclusive.

Fraser Cain: 

The worst kind of conclusive.

Dr. Pamela Gay: 

Yes. One of the experiments was like, there is life. And then everyone's like, no, no, no, no, this must have a different explanation.

And then the third one was like, I got nothing. So we have yes, no. And did we take into consideration everything we should have?

And this has led to squabbling that persists to this day, to this day, right now, as we are recording this, the National Academy of Science, there is a two day meeting going on, on astrobiology and signs of life, where they were discussing these experiments this morning. So literally to this day, on this day, this is getting discussed. And so the thinking was, some people were like, yes, there is present day microbial life on Mars, and they will go to their graves arguing even for lichens.

And then the majority of the field, which is honestly over it with all of the people claiming aliens is like, no, Viking did not prove anything, it did not prove anything. And so from the 1970s until the early 2000s, everyone was like, no, Mars is dry, Mars has never had water, we're going to explain the canyons, we're going to explain everything that looks like fluid flow, as aeolian processes, which means wind, it is the coolest word. And not fluvial processes, which means water, less cool of a word.

And then we started landing landers again.

Fraser Cain: 

But I think the, I mean, more than just landing landers, there were orbiters, there were images from the, from orbit, that told a story that was really hard to explain by wind patterns alone, that you're seeing craters, where rivers are flowing into them, and rivers are flowing out of them, you are seeing features that can really only be explained by moving water. And, and, and that I think, so then, they sort of, you know, the way they described is they went back to the beginning, they ripped up the foundation, went back to first principles and said, okay, let's just start by telling the story of this, of Mars. Let's just like, was there ever liquid water on Mars?

And if we can get to there, then was there liquid water on Mars for a long time? And if we can get there, then were there organics on Mars? And then are there any indications that there is or was ever life on Mars?

Like it was like, we are going to no longer make this argument inconclusive.

Dr. Pamela Gay: 

And this was the follow the water plan. And so in 2003, we had a new orbiter arrive that started delivering high res images. And we started getting neutron measurements indicative of frozen water.

And what was really interesting was the 2003 Lunar and Planetary Sciences Conference, the headliners were all alien processes, it's wind. And at the end of the session, which is usually when people's brains are dead and they're no longer taking notes, was when you'd hear the, but Fluvial explains this better. Let me count the ways.

And then a couple of years later, we finally had Spirit and Opportunity get to the surface. And as Spirit and Opportunity climbed around, looking at the landscape, we were finding things like these cracked mud landscapes that I listened to the words I just used to describe it, cracked mud.

Fraser Cain: 

Cracked mud, yeah.

Dr. Pamela Gay: 

And suddenly, the language that was headlining changed to water processes.

Fraser Cain: 

And so you're still sort of living in this, this seems to indicate cracked mud, this appears to indicate water, but then you're seeing things like the famous blueberries, concretions. So you talked about cracked mud. Yeah.

And that was just one. I mean, there were a lot of smoking gun evidence. And I think one of the ones that was most exciting people are probably very familiar with were these spherules or these Martian blueberries.

Dr. Pamela Gay: 

So these were actually discovered by the Opportunity rover. Again, part of that Spirit and Opportunity pair of rovers. And these were the kind of small minerals that we really only expect to be formed in water.

And it got people thinking, okay, so how do we need to rewrite the history of Mars to make sense of this? And the revolution started there. And Spirit and Opportunity had a lot of really good equipment.

They had their stereoscopic vision, they had arms, they could drill a bit. They had some spectral capacity, but they didn't have that dig deep and they didn't have the power necessary.

Fraser Cain: 

All right. So Spirit Opportunity said, okay, yes, there appear to be geological traces that water was acting here on the surface of Mars. But it was you could have had a deluge and then it was over one rain four billion years ago and then it was over and then the world was dry forevermore.

And that is not conducive to life. So NASA said, okay, let's build up the picture. How long was water present on the surface of Mars?

Dr. Pamela Gay: 

And this is where we saw a trio of missions that started with Mars Phoenix, which was launched in 2007, landed in 2008. And its sole raison d'etre was to identify water. Flat out, is there water ice?

It went to a polar region. It had a scoop. It had an amazing social media campaign and it landed on the surface.

It went scrapey scrapey. It revealed white stuff and the white stuff sublimated exactly the way water ice should sublimate. There it was.

Fraser Cain: 

Right. And you look at Mars in a telescope, you see the polar ice caps like there is water ice. But it is hard as a rock ice at the poles.

Question is, is it mixing with the regolith at more southern latitudes?

Dr. Pamela Gay: 

It was 68 degrees north.

Fraser Cain: 

Right. So you're seeing that water ice is blended in to the regolith just below the surface in the one spot that Phoenix landed. And so it must be in other places as well.

Dr. Pamela Gay: 

And this was where we also saw discussions start to arise about the dark stripes that were getting seen. Is that water? Is there brine beneath the surface?

So all of that was coming out. And this led to funding of Curiosity rover and InSight lander. InSight went with a seismograph looking to see if Mars was still geologically active.

It went with equipment to drill that failed spectacularly and was the most amazing we're going to problem solve this ever. InSight is amazing. And then Curiosity was sent with a radiothermal generator, which is a lump of nuclear materials that as it decays, generates heat, generates power.

So with its radiothermal generator, it had more power to be able to do more science. And it also carried with it a sample analysis ability that we had never had before. So the sample analysis at Mars SAM, located in Curiosity's belly, had the ability to take samples and twice, which is not a lot, but it had to carry chemicals with it to drop on the samples it scooped up.

So the samples that it scooped up, the chemical it dropped on allowed it to break apart organics to see what are these complex molecules made of. The first paper to come from this just came out. They did a sample at Mary Anning.

This is the name of the rock. It's named after the woman in Dover that the seashells, seashells, seashells. Yeah.

That tongue twister that I am incapable of saying is actually because of her. She collected fossils and sold them to take care of her family.

Fraser Cain: 

She sold seashells by the seashore.

Dr. Pamela Gay: 

And she was also like the first citizen science, but also became a leading paleontologist. Awesome story. Go read it.

They named this rock after her. That's awesome. And they found 20 organics that had never previously been seen on Mars in the broken up much bigger molecules.

And so this is one of the amazing wet chemistry labs that they're able to do with Curiosity. And Curiosity's early successes led to the launch of Perseverance rover, which is in Jezero crater. So Gale crater is clearly a former lake.

It has Mount Sharp, which is the central peak of the crater. It has been climbing Mount Sharp, looking at organics at different places as it goes. Jezero crater is another previously filled with water crater, but its wall collapsed, creating this amazing river delta.

And while crossing the river, it came across, it's called Sapphire Canyon where this river about Perseverance. So Percy over in Jezero crater had been going through Sapphire Canyon where this river used to flow and came across what they've named the Bright Angel Formation. And this was about a year ago.

And with all the capabilities that this little rover has, they poked and prodded this rock and the organics they're finding are completely consistent with a biosignature. Now they can't say for certain that there was life on Mars. They don't have the capacity.

Percy did its best. It could only get us so far. We need to do a sample return.

We have canceled our sample return. We hate everything right now.

Fraser Cain: 

Yeah. All right. So just to sort of recap the story so far, right?

The purpose of Curiosity was to say, was there water acting on the surface of Mars for a long period of time? And in the crater that it landed in, climbing the flanks of Mount Sharp, it found ample evidence that this place was not only wet once, but it was wet for a long time that the rains fell, the crater filled, that this was a lake. Yeah.

And that water was doing water stuff for a very long time. Curiosity kind of nailed that. So then you move on to that next step and you say, okay, then were the conditions habitable for life for a long period of time?

And this was the purpose of Perseverance. And so in addition to it confirming that Jezero crater had water acting on it for long periods of time, it also found that the conditions were... The stuff of life.

It found the stuff of life, that the conditions were reasonable, that if we dropped Earth life down, it would stand a good chance of surviving in this environment. And then, as you said, found some really exciting, and this is fairly fresh stuff. I mean, we're talking within the last year here from an exploration mission that has been in this new phase since Spirit and Opportunity.

I mean, we are 20 years into Let's Find Life on Mars V2. And we are now getting to the point where there is a rock. There are chemicals in that rock, which we'll talk about in a little more detail here, that the scientists have said, we've tried to explain it in every non-life way that we can.

And we have come out, we've run out of ideas. Someone, please explain this rock.

Dr. Pamela Gay: 

Right.

Fraser Cain: 

Now, obviously, other astrobiologists are saying, hold my beer.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

Right? I got plenty of explanations.

Dr. Pamela Gay: 

But that's the thing is they said, hold my beer. And they said, give me my beer back. I got nothing.

Fraser Cain: 

Hold my beer. No, I'm getting my beer back. Okay, one more time.

No, wait. Yeah, yeah, yeah. And I think you're exactly right, which is that we are now, we have gone as far as...

I mean, obviously, we can get farther. I mean, if we saw a fossil, right? If we saw a stromatolite, if we saw something really exciting.

Dr. Pamela Gay: 

But they've seen things that look exactly like stromatolites.

Fraser Cain: 

I know, I know, I know, I know. But if we did see a Mars bunny run by, then that would be more evidence, right? But now we need that sample returned because there is only so much lab equipment you can pile into these rovers.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

We need to bring these things home.

Dr. Pamela Gay: 

And Rosalind Franklin just doesn't have it. It's... Rosalind Franklin rover is several-year-old technology because this poor rover got cursed by the Russian-Ukrainian war and losing its launch vehicle and a bunch of other stuff.

The US has canceled all NASA-funded missions to Mars in lieu of commercial missions to the moon. And we have these samples scattered all over Mars that just need someone...

Fraser Cain: 

No, not sampled. In Perseverance's sample collection...

Dr. Pamela Gay: 

So it's left caches as it goes.

Fraser Cain: 

It has done both.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

So it has taken samples, put them inside its special sample collection apparatus, and then it has taken backups and dropped them on the landscape behind it. And so you could either meet up with Perseverance, hand over the samples, put them on your return vehicle, bring them home to Earth, or you could chase down the pathway that Perseverance has traveled and pick up samples that are lying there on the surface of Mars. Both are options.

Yeah. And that you get 20 or whatever of the finest, most interesting samples that the scientists on Earth were able to direct Perseverance towards into the hands of the biggest labs on Earth, you are going to make some magic.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

But this is not... We're not going to trauma dump. This is not a grieving session here where we are just going to whine about a lack of a Mars sample return mission.

We want to...

Dr. Pamela Gay: 

Celebrate what's been discovered.

Fraser Cain: 

Yeah, we want to bring you right up to speed with what is the cutting edge of the search for the story of life on Mars.

Dr. Pamela Gay: 

And it's really amazing. And the details are still coming out. It takes time to analyze results.

We're going to continue to see new results about Bright Angel Rock. I'm having to be so careful during this episode because I read a paper that is not yet published that I'm working on putting together press stuff for. And it's so cool, people.

And so here we have a river delta that has essentially been fossilized in place. And there's so much other cool stuff on Mars. There was work done a few years ago where by looking at how the landscape was altered in response to water, they were able to identify where tsunamis have historically taken place.

So you can imagine one of these crater lakes that gets thwomped by either a landslide or an incoming meteor, both. And as a result, a tsunami moved across the crater lake. And there's some evidence, this is still being discussed, how long it would have lasted, that the reason that one side of Mars is at a radically different altitude than the other is there used to be an ocean.

And so what we're seeing is the ocean floor and the continental landmasses, sands, ocean. I just love that idea. Kevin Gill has amazing graphics related to that.

We used one of them for the slide cover for this video. Go look at Kevin Gill's work. It's science-based.

Fraser Cain: 

And this is like a multi-country exploration. So we got a really interesting discovery from the Chinese rover, Tianwen, which found, it was able to map the ancient shoreline. They've targeted the landing site for Tianwen to be at what was thought to be the ancient shoreline.

And it was able to map out and see that, yes, indeed, this was the place where water was probably lapping at the side of an ancient sea for a very long period of time. Very exciting. So again, the evidence is building.

Now, the Chinese are going to be sending a sample return mission. Tianwen 3. And yeah, and it's going 28?

Dr. Pamela Gay: 

It launches in 28. It lands in 2031. And they're not going to have a multi-year rover ahead of it collecting samples, but they are going to carefully target where it lands.

It's too early to know where it will land at this point.

Fraser Cain: 

Grab something interesting nearby, put it on a rocket, send it home. So we will, by the middle of next decade, well, early next decade, get our hands on a fresh piece of Mars, which is pretty exciting. Not as good as the best samples Perseverance could find, but it is still a good first step towards getting some samples from Mars.

So do you think, like, are we now in the endgame of the V2 search for life on Mars?

Dr. Pamela Gay: 

I don't know if we're endgame yet, just because time scales are so wibbly wobbly. I mean, that's the thing is our exploration of Mars is limited by the technology we've been able to land, which is where Percy did the best it could and said, I think biosignatures, but we can't prove it without a full laboratory of equipment that has a whole lot more power than that little robot has. The helicopters we're planning to send aren't going to be able to do chemistry.

Fraser Cain: 

Right. The skyfall.

Dr. Pamela Gay: 

Yeah. And so the endgame question is, when are we going to bring back the right samples to incontrovertibly say, yes.

Fraser Cain: 

Yeah. And I think, like, I'm sure people who are listening to this right now, their thought is, well, aren't humans going to go to Mars? And so can't they do this in the same way that humans went to the moon and the tech stack for sending humans to Mars and bringing them safely home to Earth is the same thing, but vastly more complicated than sending a robot, picking up a bunch of samples and bringing them back home to Earth.

The robots are hardier. They can handle a lot more. So if you can't do the first thing, then you can't do the second thing.

Right. And your other option is we'll send the humans and then send good lab equipment. But again, good lab, like we're talking devices that are the size of a small building.

Right. You cannot take one of those and put them on the surface of Mars. You really want to bring that stuff back home to Earth.

And so I think you're going to see that gate be, can we get good samples back from Mars that allow the scientists to conclusively search? And I think a great analogy of this is what's happening with the samples of Ryugu and...

Dr. Pamela Gay: 

And Bennu.

Fraser Cain: 

Bennu.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

And we're seeing these just little whiffs of asteroids... Amazing science. ...turning into some of the most incredible discoveries that science has made about our understanding of the history of the solar system. I mean, they are finding amino acids. They are finding ratios of water to deuterium. Yeah.

They are putting together the history of the solar system in a way that you just have never been able to do with the meteorites that the solar system has deigned to drop on our planet up until this point. So yeah. Endgame is sample return.

Dr. Pamela Gay: 

I'm hoping that we can do fossil hunting while we're both still alive. That is my dream, is fossil hunting on Mars.

Fraser Cain: 

Fossil hunting on Mars. Yeah. Walking around, chipping open a rock, looking inside.

Dr. Pamela Gay: 

I mean, it can be a robot. It can be a super powerful robot.

Fraser Cain: 

Yeah. Yeah. But why not...

I like to go with a little hammer and chip away at rocks and look for fossils inside. So let's let an astronaut do that too. That might be a good use of astronauts.

Dr. Pamela Gay: 

It's true. It's something that I've always said I hope to be a little lady fossil hunting on Mars. I think I'm just a little bit scarred by the double boom of Starship's booster and Blue Origin's New Glenn.

So last week was a really bad day. And currently we have Starship, New Glenn, and Vulcan all grounded.

Fraser Cain: 

Yes. Yeah. We are not go for launch.

Dr. Pamela Gay: 

We are not go for launch.

Fraser Cain: 

Right. All right. Well, Pamela, that was awesome.

Thank you.

Dr. Pamela Gay: 

It was my pleasure. And thank you to all our patrons. Some of you have realized you can get me to say truly ridiculous things by having truly ridiculous usernames.

To those of you who make me laugh, I salute you. To those of you whose names I'm about to mispronounce, I'm just really sorry. This week, we would like to thank Adam Anise Brown, Alexis, Andy Moore, Astro Bob, Bart Flaherty, Benjamin Mueller, Bresnik, Bruce Amazine, Christian Bergholt, Cooper, David Fines, David Green, Dr. Whoa, Ed, Evil Melky, Frank Stewart, Jeff McDonald, Gordon Duis, Hal McKinney, Jacob Huell, Jason Kwong, Jeremy Quarrel, Joanne Mulvey, John Drake, Jonathan H. Staver, Justin Proctor, Katie B., Kim Barron, Lab Rat Matt, Les Howard, Mark, Mark Thompson, Matthew Horstman, Michael Purcell, Mike Dog, Nate Detweiler, Papa Hot Dog, Paul L. Hayden, Philip Walker, Rhythm Chameleon, Robby the Dog with the Dot, Ruben McCarthy, Sage Sinfen, Scone, Sean Matz, Seggy Kemmler, Taz Talley, Tim Garrish, Van Ruckman, and William Andrews. Thank you all so very much.

Fraser Cain: 

All right, thanks, everyone, and we will see you next week.

Dr. Pamela Gay: 

Bye-bye.

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