This Week in Space 220: First on Mars

Summary

Podcast Summary: This Week in Space 220 – "First on Mars"

Release Date: July 24, 2026
Host: Rod Pyle (Aster Magazine), Co-host: Tariq Malik (Space.com)
Guests: Dr. Penny Boston (NASA Astrobiology Institute; cave expert), Dr. Pascal Lee (Mars Institute, SETI Institute, planetary scientist)

---

Episode Overview

This special edition of This Week in Space celebrates the 50th anniversary of the Viking 1 and 2 landings—the first successful landings on Mars. The episode brings in two leading experts, Dr. Penny Boston and Dr. Pascal Lee, to examine what Viking really found about life on Mars, how the mission influenced planetary science, and where the search for Martian life could go next. The episode is a balanced mix of current headlines, personal stories, and deep dives into astrobiology and Mars exploration.

---

Key Discussion Points & Insights

1. Space News Headlines (03:19–09:30)

• SpaceX Starship Flight 13 Delay:
  • The much-anticipated 13th flight is behind schedule due to several issues including engine problems and weather concerns.
    • “Where’s the beef, indeed, Rod. We’re actually over a week late now for this launch.” – T. Malik (03:29)
• SpaceX Land Swap Controversy:
  • SpaceX’s plans to expand Starbase in Texas are hit by lawsuits from conservation groups over a proposed land swap with the Lower Rio Grande Valley National Wildlife Preserve. Concerns center on habitat loss and the impact of rocket launches on protected species. (05:01–07:37)
    • “There’s a wildlife group that is suing… saying this is not right. They don’t want this land swap...” – T. Malik (05:56)
• Chinese Rocket Struck by Lightning:
  • China’s Long March 3B rocket launch mirrored the famous Apollo 12 incident—struck by lightning but still succeeded. Spectacular images circulated online. (07:37–09:30)

---

2. Guest Introductions & Origin Stories (11:38–21:49)

Dr. Penny Boston

• Former director of the NASA Astrobiology Institute and renowned cave (“speleology”) researcher.
• Her journey began by reading science fiction at age 6 and being inspired by articles from Frank Drake and Carl Sagan in “My Weekly Reader.”
  • "When I read that, I was like, hot dog. That’s kind of it." – P. Boston (15:49)
• Transitioned from aspirations in astronomy and oceanography to astrobiology through biology, geology, and atmospheric chemistry.
• Her work with Carl Sagan and a National Geographic cave feature launched her into planetary science and exploring the subsurface as a last, best place for Martian life. (15:06–18:25)

Dr. Pascal Lee

• Planetary scientist, artist, and Carl Sagan’s last teaching assistant at Cornell.
• Inspired by sci-fi and Carl Sagan's books, especially “The Cosmic Connection.”
  • “It became a location as opposed to…just some celestial body. It became a landscape.” – P. Lee (19:35)
• Leads analog Mars expeditions in the Canadian Arctic (Houghton Mars Project), recently identified a previously overlooked volcano on Mars.
• A voice for bold, multidisciplinary exploration in planetary science. (18:37–20:45)

---

3. Historical Context: Viking, Mars, & Early Exploration (21:54–28:05)

• Pre-1965 ideas about Mars were speculative, drawn from telescopic images and maps by Lowell—“canals” and the idea of intelligent Martians.
• Mariner 4 (1965) provided the first close-up images—revealed a barren, moonlike Mars, dashing popular expectations.
• Mariner 9 (1971) and subsequent Soviet Mars program (Mars 2 & 3) began to change views, but only Viking in 1976 successfully landed with advanced scientific capabilities and a bold focus on life detection.

---

4. The Viking Landing Experience (28:05–32:41)

• Both guests share the emotional and historical impact of the first Viking images:
  • Lee: Underwhelmed by the first footpad image but later blown away by panoramic views, which made Mars a real, tangible place for people on Earth.
    • "It became a location…so beautiful." – P. Lee (28:07)
  • Boston: Remembers the footpad image as a ‘first footprint’ and a transformative, almost mystical moment.
    • “It was a complete mind shift…hooked on Mars and so were my contemporaries.” – P. Boston (29:18)
• Technical note: The first images focused on the footpad to confirm lander safety on potentially unstable terrain. (31:35–32:41)

---

5. Viking Life-Detection Experiments: Why Are We Still Debating? (34:11–43:42)

• Why the debate continues:
  • Viking’s life-detection experiments were designed before many advances in microbiology and with little knowledge of extremophiles or Martian geochemistry.
  • Boston lists over 40 things unknown at the time—from extremophiles to genetic sequencing. (34:50–37:26)
    • “Should we have waited till we got smart to send such a mission? No, you cannot start exploring when you know everything ... you have to explore.” – P. Boston (36:13)
• Breakdown of Experiments (Pascal Lee):
  • Three main biological tests:
    • Pyrolytic Release: Looked for photosynthetic organisms; soil showed activity in both light and dark, suggesting chemistry not biology.
    • Label Release (Gil Levin’s experiment): Generated positive results, but debate continues whether it was biology or soil chemistry (e.g., perchlorates mimicking life).
    • Gas Exchange: Results pointed to unusual chemistry, again, not clearly biology. (37:44–43:42)
  • Most scientists now believe Viking detected highly reactive, oxidizing soil chemistry, not biology—but a vocal minority, including Gil Levin, still argues for life.

---

6. Human Stories, Controversies, and the ‘Wolf Trap’ (45:51–50:47)

• Debates Between Experiment Leads:
  • Gilbert Levin remained convinced his experiment detected life; Norman Horowitz was vehemently opposed and dismissive.
    • Boston recounts Horowitz discouraging her as a young scientist from pursuing astrobiology ("…told me that I should change my career path…of course, I studiously ignored him…" (47:50–47:53))
• Lost Opportunity (‘Wolf Trap’ Experiment):
  • The only experiment resembling Earth-based, non-reductionist microbe detection was cut for cost, which might have clarified the ambiguous results.
    • "It was a pity that it was removed because it would have been a clear indicator." – P. Boston (49:17)

---

7. The Future of Mars Life Detection: New Frontiers in Caves & Organics (55:06–63:06)

• Why Caves Matter for Mars Life (Penny Boston):
  • Caves provide natural shielding from radiation and harsh surface conditions—possibly “oases” for relic biospheres.
  • Environments within can retain ice, display unique chemistry, and host life forms (extremophiles) unknown on the surface.
    • "As a refugium, as a refuge for life..." – P. Boston (56:56)
  • Advocates using drilling tech in caves and expanding beyond reductionist approaches—seeking biosignatures, protein chirality, etc.
    • “If you could identify … proteins made of different amino acids…bingo, you have found a biosignature that is unquestionably alien life.” – P. Lee (61:34)
• Recent Perseverance & Past Rover Results:
  • Perseverance and Curiosity have detected complex organics, but none definitively biological.
  • Notable discovery: “Leopard spots” in the Cherjeva Falls Rock—could suggest biology but are not conclusive absent more definitive in-situ analysis. (72:04–74:42)
  • “Not enough data.” – P. Boston (62:58)

---

8. Planetary Protection & Mars Sample Return (66:03–74:42)

• Spacecraft Sterility:
  • Viking landers remain the cleanest ever launched, although true sterilization is nearly impossible for such large systems.
    • “Viking 1 and 2 landers were on record as being the cleanest spacecraft ever launched.” – P. Lee (66:03)
• Planetary Protection:
  • Essential to avoid both forward (Earth life to Mars) and backward contamination (Martian life to Earth humans/systems). Viral dangers are taken seriously.
• Views on Mars Sample Return:
  • Boston: Advocates bringing back Mars samples for science and astronaut safety, accepting that current Perseverance samples may not be from the most promising locations for life but still offer crucial geological data.
    • “I think that, you know, knowledge is essential before we commit astronauts to going there.” – P. Boston (70:03)
  • Lee: Sees value but isn’t fully convinced that current rock samples are worth the multi-billion-dollar cost unless more definitive signs of life are identified first.

---

Notable Quotes & Memorable Moments

• On the importance of the Viking images:
  • “It was the first footprint, albeit not a human footprint... It was a complete mind shift.” – Penny Boston (29:18)
• On bold exploration:
  • “You cannot start exploring when you know everything, because then you’ll never know everything because you have to explore.” – Penny Boston (36:13)
• On confirming life:
  • “Extraordinary claims require extraordinary evidence.” – Carl Sagan, quoted by Pascal Lee (50:21)
• On Mars cave exploration:
  • “If we look at … the proteins…if [they] are made of the same amino acids as the ones on Earth…bingo, you have found a biosignature that is unquestionably alien life.” – Pascal Lee (61:34)
• On perseverance and mentorship:
  • “He [Horowitz] basically told me that I should change my career path because everybody would always consider me a dilettante and not serious... Of course, I studiously ignored him in every possible way.” – Penny Boston (47:53)
• On the dangers of Martian viruses:
  • Nobel laureate Barry Blumberg warned Lee that Martian viruses could kill all life on Earth (68:10)

---

Key Timestamps

• SpaceX/China headlines: 03:19–09:30
• Boston/Lee introductions, origin stories: 11:38–21:49
• History of Mars exploration until Viking: 21:54–28:05
• Viking landings & emotional impact: 28:05–32:41
• Why are Viking’s results still debated? 34:11–43:42
• Experiment details and controversy: 43:51–54:21
• Caves & astrobiology (Boston/Lee): 55:06–63:06
• Planetary protection; sample return: 66:03–74:42

---

Closing & Where to Find Guests

• Penny Boston:
  • NASA websites; gives frequent talks; based at NASA Ames (Kirtland AFB, NM)
• Pascal Lee:
  • Mars Institute, SETI Institute, pascallee.net for art

---

Summary Impressions

This episode masterfully blends historical reflection, scientific depth, and human stories. The debate over Viking’s legacy remains vital—and unresolved—making the search for Martian life an ever-fascinating pursuit. Both guests urge the next generation of exploration to think boldly, interrogate the subsurface, and appreciate both technological achievement and scientific humility in the search for life beyond Earth.

---

Recommended for: Anyone interested in planetary science, the history and future of Mars exploration, and the intersection of science, technology, and adventure.

Transcript

[A]

Coming up on this Week in Space. It is launch day for SpaceX's Starship Flight 13. A Chinese rocket gets struck by lightning. And it has been 50 years since NASA's Viking 1 and 2 Mars landers touched down on the red planet. And we are still debating if it found life or not. And with us today are doctors Penny Vossnan and Pascal Lee to discuss exactly that. What we found, what we learned, what's to come. Check it out.

[B]

Podcasts you love from people you tr.

[C]

This is trit.

[B]

This is this Week in Space, episode number 220, recorded on July 24, 2026, first on Mars. Hello everyone, and welcome to another episode of this Week in space, episode number 220 that we like to call the first on Mars edition. I'm here with my very good friend, editor in chief of your favorite online publication, space.com. tariq Malik. How are you?

[A]

Hello. I'm doing well, Rod. How are you doing today?

[B]

I'm very good. Very glad to see you here. And I of course am editor in chief at Aster magazine and that is published by the National Space Society for your consumption in a bookstore near you. Now today we're going to be talking to Dr. Penny Boston, who's the former director of the NASA Astrobiology Institute and an astrobiologist. And this is a new word for me, so you'll have to bear with me. Splayleologist, which means she likes caves.

[A]

It's the study of caves, everybody.

[B]

Yes, thank you. And returning guests are Dr. Pascal Lee, a planetary scientist with the Mars Institute. And we're going to be Talking about the 50th anniversary of the first successful landing on the red planet by Viking1. Yeah, and that's exciting. But first, we have two space jokes from Tucker Drake.

[D]

Also,

[B]

Rod and Tarik were stranded on Mars. Rod said, I'm so lonely I could cry. Tarek said, what do you mean lonely? I'm here. And Rod said, that's what I mean.

[A]

That's par for the course.

[B]

Okay, let's do a nice one. Hey, what goes Ha ha ha. Thump, thump, thump.

[A]

I don't know, Rod. What?

[B]

A three headed Martian laughing his heads off.

[A]

Oh, no. Okay, that's good. That's good. Very Mars appropriate. Very appropriate for today.

[B]

Now, I've heard that some people want to lop our three heads off when it's joke time of this show. But you can help by sending us your best, worst or most different space joke at Twistwit tv. We'll be happy to give you credit or blame it on you depending on how the response goes. All right, let's go to one quick headline here.

[A]

Yeah, well, we should, we should. Actually, you mentioned that I was supposed to do this at the start. But just for folks who are just joining in from Space.com, this is the first time that we've actually done this show live on space. So welcome everybody there. Hope you enjoy the show. Obviously, we've been doing this for a while, 220 episodes in, but it's every Friday and we're gonna talk about Mars today and it's a really big special one. That's why we're live on the site right now. But maybe it's something we'll do in the future. But let's talk a little bit about what's coming up. Let's talk Brad.

[B]

Yeah. And everybody make sure you tell Tarik and his people how much you love this so we can do more of it in the future. All right, so let's actually cover a couple of quick headlines here.

[A]

Yes.

[B]

So we're all waiting t tapping our feet tip, tap, tip, tap, tip tap on SpaceX's Starship Test Flight 13.

[A]

Where's the beef, Mr. Yeah, where's the beef indeed, Rod. So we're actually over a week late now for this launch. You might recall the last week, in last episode we talked about how SpaceX had to abort the launch just at like the T minus zero mark. They had a few engines that didn't ignite on time and so they stood down for several days, well, about a week now, to replace a couple of those engines and then hopefully they'll get to it. They were supposed to launch a day before. We're recording this on Thursday the 23rd. They stood down from that because of bad weather, or at least cloudy, obscured weather above their Starbase Texas, South Texas launch site. They want clear skies because they want to be able to see, I believe, like the boosters on the way up, you know, to see how all the new bells and whistles have done so. The launch is now set for hours from now as of recording 6:45pm on Friday, July 24. If you're listening to this on the weekend, it might have launched already. Go back and watch the video. It'd be really cool to see. But this is going to be their big 13th flight. Not superstitious, Rod. The SpaceX crab. Not at all.

[B]

Being SpaceX, this might be the one that works, you know. Boy, you know, it's been, it's been a long crawl for this system.

[A]

And this is only the Second launch this year of Starship. Yeah, the first one was that big

[B]

moon clock is ticking pretty loud.

[A]

Mm. So, speaking of that, we're talking about Starship, we should talk about what else is going on in Starbase.

[B]

Yes, there is. There is another problem staring down Starbase. What is it?

[A]

Yeah, also, like, as. As you mentioned, Rod, SpaceX has this ticking moon clock with NASA's Artemis program that they have to deliver to try to get people back on Mars or on the moon. Back on Mars. Back on the moon. I got that on the brain today. By 2028, in order to do that, they have to launch a lot of starships, starship after starship after starship, to test all the different technologies. And so they want more land to be able to do that at Starbase. And they're trying to give up some of their land that they have there and then acquire about 727 acres of the Lower Rio Grande Valley National Wildlife Preserve. And so in exchange, they're going to give up something like 683 acres. It's a land swap. And that way they can have a bit more space to do what they need to do. They'll have more buffer zone if they have issues, because, you know, they've had a few booster failures in the last year or two or whatever, and then that way they can, I guess, they can grow over time. Well, there is a wildlife group that is suing Texas, a conservation group, saying this is not right. They don't want this land swap because the public and the nature wildlife are going to lose clearly preserved public lands right now. And some of the lands that SpaceX is giving up in return for this are not connected to the wildlife program. So they're kind of. They're kind of patchy all around. And so this is still working its way through the system. And it might be something that affects what SpaceX can or can't do in terms of, like, their launch cadence or how much land, or if they have to expand to add more sites. They've already added a second launch pad at this Starbase facility, that sort of thing going forward. So it is something to watch because it is not resolved at this point in time. SpaceX has worked out this plan with the US Fish and Wildlife situation, but this conservation group is really trying to block it right now.

[B]

Well, and we should bear in mind that when SpaceX originally announced Starbase, it was going to be for Falcon 9 launches, correct?

[A]

Falcon Heavy. Actually, it was supposed to be for Falcon Heavy, and it was going to be like their Big launch site to ramp that whole thing up. And then they came up with the starship plan, which is much, much larger than.

[B]

With much bigger fireballs, and things go wrong.

[A]

Well, and also just the sound of the launch alone, you know, can destroy some of the nests and like the other wildlife that's there. And it's happened already. And so that's why these conservationists are really concerned, because there's a lot of protected species that call this area home. And they're being affected very clearly by these repeated launches over time.

[B]

Well, speaking of a place that may not care quite as much about cracked eggs and trees, the Chinese had a rocket launch. What was it? Yesterday? Yeah, it was yesterday, which was reminiscent of Apollo 12, which I was just writing about in the book I'm writing about flight director Jerry Griffin. His first shift as flight director for Apollo was on the launch of Apollo 12, which got struck by lightning twice. Knocked out the guidance system and the electricals and everything else. It was quite a pucker moment, as he calls it. What happened in China?

[A]

Well, you kind of spoiled it right there for everybody. Yeah. With your Apollo 12 comparison because China launched a Long March 3B rocket yesterday and it too was struck by lightning. And it wasn't just struck by lightning in silence. And this is really just a show and tell because the image is absolutely striking, Right? Oh, right. No, yeah, but I'll be okay. So, so as it, as it lifted off, and this is this. It lifted off from Tinus, and I hope I pronounced this correctly, the Shisheng satellite launch center, it's carrying a communications relay satellite that's. That was going to geostationary orbit. And about a half minute into the flight, it was struck by lightning and it was witnessed by crowds of people who are out there. So there's all of these videos on social media and we got this photo from Getty here. But. But there is so much more out there happening in real time. And of course, like, it went all the way to space as, as one does apparently. Right. It got up there, did its. It did its thing. The satellites in orbit now. So it didn't fail, which I think is a testament. Right. Because you do not want your rocket to fail if it gets hit by lightning. And, you know, like you mentioned, it happened during Apollo 12. And no one really wants to see that because that could be a really bad day if it goes wrong. So it does say something. These Long March rockets can withstand that.

[B]

All right, well, that's it for headlines. We will be back in just a moment with Dr. Penny Boston and Dr. Pascal Lee. So stay with us. Hey, guys. This episode of this Week in Space brought to you by Rippling now. These days, you can chat with AI about almost any business problem, but only rippling AI is built to solve them specifically for your business. What makes rippling AI different? It's built on your live global workforce data. One platform, one unified source of truth with all your business systems connected from day one. And that means rippling AI can operate with the full context of your live business, surfacing insights and taking action using your org chart, your payroll, your device inventory, your compliance obligations, and more. Now, let's say you want to focus on talent retention. All you gotta do is ask rippling AI who are my top performers this year? And you'll instantly receive a workforce report highlighting your highest performing employees. With supporting data like comp ratios, recent performance reviews and engagement metrics, Rippling AI is then able to turn those insights into real action. In this case, it might recommend, let's say, a retention strategy that includes a, oh, I don't know, 10% spot bonus for top performers. And because permissions are automatically inherited and actions flow through your existing approval chains, all you have to do is review, tap, confirm, add the bonus right there to the next payroll run.

[A]

It's that easy.

[B]

Don't settle for AI. That's all talk. Head to rippling AI slash twists and get the only AI built to give you full visibility across your business and take complex actions across your entire organization. That's rippling R I P P L I N G. Sign up for exclusive access today. Rippling AI slash twis. And now let's go back to space. Thanks, guys. And we are back with Dr. Penny Boston and Dr. Pascal Lee. Hello, both of you. Thanks for joining us today.

[C]

Good to be here. Thank you.

[B]

Dr. Lee is a planetary scientist, geologist and artist. And you all know that because he's been on the show at least a dozen times. But new to us is Dr. Penny Boston, who is an astrobiologist. And Penny, I think I butchered this before, but spleologist. Did I get that right?

[D]

Speleologist.

[B]

Speleologist. Oh, I added an extra L there. Sorry about that. Which means you love holes in the ground.

[D]

I love holes in the ground.

[B]

And the former director of NASA's Astrobiology Institute. And you also work with the Carlsbad National Monument and New Mexico Institute of Mining and Technology, right? Can you tell us a little that?

[D]

Yeah, I actually was the associate director of that for a long time when I was a professor at New Mexico Tech. And that's a federally mandated institute to care for the science and the conservation and welfare of cave resources of all different kinds in the United States. So there are, you know, there are laws on the books to protect caves. The Cave Protection act of. And then it's its updated version years later. So they are the mast head, essentially, for cave studies, science, conservation, and enjoyment in the United States.

[B]

Well, I have yet to go, but I sure would like to. And of course, Pascal, if you've ever watched the show, but I'll assume that you haven't, is a planetary scientist with the Mars Institute and Ames Research Institute, Ames Research Center, Northern California, a NASA facility, and runs the Houghton Mars project up on Devon island in the Canadian Arctic, which is a very cool thing to do. And recently discovered a volcano on Mars that we had all been staring at since 1971, but it took you to figure it out.

[C]

Thank you, Rod. Good to be here. Penny is modest. She. She is known in space and planetary science as being a pioneer in the exploration of caves anywhere we can and search for life in them. So I just wanted to have a chance to say that.

[D]

Thank you, fan club.

[A]

Yeah. Also, I heard that you can speak Klingon, too, Penny. I think that's awesome.

[B]

Oh, yeah, That I hadn't heard.

[D]

It's fairly notorious. When I was still a professor, I gave the. The graduation speech at Mexico Tech, which is a very geeky school.

[B]

Oh, my gosh. Was there a translator?

[D]

No.

[B]

Yeah, I'm not kidding.

[D]

When I started speaking school.

[C]

Wow.

[B]

That's pretty amazing. All right, Tarek, I know you have a question, and then we'll move on to Viking 1, of course, which is why we're here.

[A]

Yeah. Well, as. As fans of and listeners of our show will know, I always like to kind of find out people's paths to space and in this case, to Mars in particular. And I know, Pascal, We've. We've talked about that repeatedly, but. But, Penny, we've actually never heard how you got interested in space in the first place. Maybe also in caves in the first place. And then what led you to the space research that you do now and. And then maybe your first interest in Mars.

[D]

Well, let me give you a capsule summary. I mean, as you guys know, we've just passed the 50th anniversary of Viking, so that was a major linchpin in my career. But it started, really, when I was a little kid. So I started reading science fiction when I was about 6, and I already knew I wanted to go into space and look for Weird creatures with tentacles and stuff. And, you know, in those days in elementary schools in the United States, we had these little kid newspapers called my Weekly Reader.

[B]

Weekly Reader. Green and black ink. Yes, I remember it well.

[D]

Black ink. And it got all over you because it was probably not soy ink. And there was this one issue, and there was a little article by Frank Drake about the SETI equation, which stunned me that you could render these ideas into, you know, math, because I was pre algebraic at the time. I was about 9. And also a little article by Carl Sagan about exobiology. And when I read that, I was like, hot dog. You know, that's kind of it. And even though I toyed with a lot of different specialties, you know, did I want to go in the astronomy direction, did I want to go in the oceanography direction? I eventually settled on biology, but I didn't stay there. So I have formal degrees in, you know, biology, geology, atmospheric chemistry, and all of that set me up for, you know, eventual astrobiology, which is the coming together of so many different sciences in order to investigate life. And then I worked early in my career, I worked with Carl Sagan on a paper looking at organic material that could be made by exposure of simpler molecules to organic chemistry. And so I was well into that. And then in mid career, a friend of mine here at NASA Ames saw a National Geographic special on Lechuguilla Cave in New Mexico. There was a USGS scientist, Kim Cunningham, who was interviewed and part of that. And he said that he thought that in some of the cave decorations that he was studying, he thought he was seeing microorganisms. So I called him up and I said, we're from NASA and you don't know us, but we like to go into your cave. And that was in 1994. And in 1992, Chris McKay and I and a colleague from Russia published a paper suggesting that the subsurface of Mars would be the last best place to look for, you know, extant life. And so I had not been a caver. I had to become a caver in order to work.

[B]

All right, and Pascal, I neglected to mention earlier that you're very closely affiliated with the SETI Institute and work with them and have for how many years now?

[C]

I've been with the SETI Institute for 25 years. Yeah, yeah.

[B]

Okay, so basically it stands for Search

[C]

for Extraterrestrial Intelligence, but it does a lot more than that. It's interested in the possibility of life in the universe in general.

[B]

Okay, so give us a brief version of your origin Story, please.

[C]

Oh, I'm not worthy. But you know, interest in sci fi as a kid have always dreamt of traveling one day to Mars. Learn about Mars really through reading Carl Sagan's books. The one that I would recommend to everybody is one that's less well known than his Cosmos book. Carl wrote the Cosmic Connection. In fact, he describes his discovery of the first image sent back by Viking, which was a little grainy. The dust was still settling on Mars when they took this picture of the foot pad of the landing pad.

[B]

Right.

[C]

Anyway, that really got me going and I became a plantary scientist and eventually his last TA at Cornell before coming out to California.

[B]

So just to restate that, everybody. Pascal was Carl Sagan's last teaching assistant, which is pretty cool because you got to sit at the knee of one of the science icons of the 20th century. That's pretty amazing.

[C]

Yeah, I mean, just to say a few words about him quickly if we have time, you know, Cobb was of course this, this monument to planetary science and outreach at the same time he, he taught. His last course was a course on science writing. And I wasn't particularly qualified, but he needed one TA for that class to grade a bunch of essays every two weeks. And so he wanted also to have his TA on hand, so to grade his essays. So I spent every other Saturday afternoon in his living room grading essays. And that was just quite an experience, as one does.

[B]

All right, I think we're gonna go to a quick break and we'll be right back and we'll dive right into Viking 1 and its predecessors. So stay with us.

[D]

By the time I hit my 50s, I'd learned a few things, like how family is prec. Work can always wait. And 99% of people over 50 already have the virus that causes shingles. Not everyone at risk will develop it, but I did. The painful blistering rash disrupted my life for weeks. Don't learn about your shingles risk the hard way. Talk to your doctor or pharmacist today. Sponsored by GSK Shipping, Billing, admin, Payroll, Marketing. You're managing all the things, so why waste time sending important documents the old fashioned way? Mail and ship when you want, how you want with stamps.com print postage on demand 247 and schedule pickups from your office or home. Save up to 90% with automated rate shopping. That's why over 1 million small businesses trust stamps.com. go to stamps.com and use code podcast to try stamps.com risk free for 60 days.

[B]

So we're here to talk about the 50th anniversary of Viking 1, which was on July 20th, landing on Mars, the first, first human machine to successfully do so. But I want to just give a quick lead up. So up until 1965, we really didn't know that much about Mars. Everything was gleaned from telescopic observations. And at best, even with something like the Palomar 200 inch telescope, you got this kind of fuzzy red image. You could see some features on the surface, but they were pretty indistinct. And you know, at that magnification it's kind of breathing in and out of focus. So there was a lot intuited. But honestly, up until the early 1960s, a lot of people were still using maps back derived from the Percival Lowell era around the turn of the 20th century. And as we all know, of course, Percival Lowell is the famous astronomer at Flagstaff, Arizona, who became increasingly detached from reality, if I can say that kindly, and had gone from observing Mars to deciding that was peopled by a vastly more intelligent species than us that was trying to survive by building canals over the planet to ship water from the poles down to the equator. And as we soon found out, that wasn't the case. But in 1965, which I'm old enough to remember, when Mariner 4 went swinging past the planet in a Single flyby, snapped 22 and a half images. Very small, very low resolution, but enough to show us that Mars effectively looked like the surface of the moon. So it's pretty desolate, pretty dry. They did a radio occultation experiment which shot a radio beam through the limb of the planet as it was departing its flyby and also let us know that the atmosphere was extremely thin. So that was kind of a letdown that sort of took the wind out of a lot of the sails that we had. If we had been fans of Ray Bradbury and others. Then in 1971, Mariner 9 orbited Mars and actually stayed in orbit and was able to take a couple thousand photographs. And these were of a much higher order of resolution. And you started to see these pretty obviously watery roaded features all over the planet. So it was a real shift in how we looked at this, what we assumed was a moon like world. Now clearly at one point had weather and had weathering and these, these scraped features. So that certainly got everybody's attention. And of course that was when the first photographs came down of Pascal's Volcano, although nobody recognized as such at the time or for decades after. And Penny, you said you have a Bunch of Mariner 9 photographs. That's really something.

[D]

Yeah, I do. You know, one of my dear friends from childhood was a grad student at MIT at the time of Mariner 9. And, you know, they, they had sort of proofs coming and they were printing them quickly and, you know, for first inspection and so forth. And so, you know, and in those days, maybe we were not quite so careful about, you know, curating things for historical purposes. And so my friends saved them and gave them to me and I have them along with, you know, a lot of our case from our study group stuff from the University of Colorado, you know, in the 80s. And so, yeah, I'm something of an antiquarian.

[A]

Okay.

[C]

Looks like I'm gonna have to pay you a visit, Penny.

[D]

Yeah,

[B]

absolutely. And then in 1971, we have the Soviet Union being very ambitious and sending two orbiter lander combinations, not, not completely unlike Viking 1 and Viking 2 out to Mars. Mars to the first of the twins, crashed onto the planet, but it got there, which was a big achievement. And Mars 3 did actually soft land and transmitted about 20% of one frame of information back. So unfortunately nothing there. And it's a shame because that, that lander, as weird as it was, and all the, all the stuff in the Soviet Union in those days look pretty strange. They had pressurized vessels on them, protect the sensitive electronics and so forth. But it actually had a little kind of gimpy mini rover on it that was attached by a cable to the lander that was supposed to be able to kind of crawl, as a generous word, but kind of lump its way forward to look around for as long as the cable was, which I think was 15ft. But unfortunately none of that actually functioned. But, but it was a big deal. I mean, it was a very daring thing they did. And normally with the Soviet Union, you know, in the case of Venus and later Mars, they just would throw pairs of probes and spacecraft out to these worlds over and over and over again until they got it right. Unfortunately, they never able to get Mars right. That waited until 1976 when Viking 1 and Viking 2 arrived. These are very large, very sophisticated spacecraft, both with orbiters and landers. The orbiters were derived from the Mariner bus and did not look terribly dissimilar, but of course had to carry more fuel to be able to break into orbit with all that mass and so forth. And then the landers were, besides having cameras and weather instruments and so forth, were really there to look for life. And that's something that I'm sure Penny's going to expand on that's something we were doing through the lens of what essentially was 1960 science. We didn't know a lot about things like extremophiles and so forth back then. So I guess I'll ask you both before we jump into that. We. Where were you when Viking 1 landed, and what was the experience like for you?

[D]

Go ahead, Pascal, I'll speak.

[C]

I was glued to the tv, I remember. But then it. I thought it was exciting, but I thought it was disappointing because the only picture they showed was that black and white picture of the footpad. And that was. It was interesting, but not that exciting. But then a few weeks later, we started seeing in the press all these color panoramas that were just magnificent. And that. That, I think, really turned Mars into a place for. For everybody. It became a location as opposed to, you know, just some celestial body. It became a landscape. It became a place, and it was so beautiful.

[B]

And I just want to insert there, Pascal, I was at Caltech when those first images came down. Unlike you, when I saw that image of the foot pad, I just went nuts, because as much as I know the reporters around me who were grousing that it wasn't a picture of the horizon, I thought there was something almost kind of mystical and romantic about looking down at the foot pad and kind of saving the best for. For later. But. But I do take your point. Penny, how about you?

[D]

Yeah, I mean, my experience is very similar. I had just moved to Colorado from Florida, where I was an undergraduate and, you know, preparing to launch off on graduate studies, and watching it, that first image come in. And in those days, you know, it was this torturously slow, rastering across and, you know, line by line. And seeing the footpad of the device did something to my brain. It was the first footprint, albeit not a, you know, not a human footprint. And as Pascal said, it became a location. In later years, I wrote a, you know, poem about it because it was an overwhelming experience. And now when you look at that image, you think, gosh, it was pretty grainy and pretty primitive, and now we're used to whiz bang graphics and everything. But at the time, it was extraordinarily meaningful. And so that changed it into a world instead of a dot in the sky, even more than the, you know, the orbital images, because it was human scale. And even though I was disappointed, there were no, you know, green Martian giraffes obviously in evidence, it was. It was. It was a complete mind shift. And I think. I'm sure a lot of people felt that Same way. And so, you know, I was hooked on Mars and so were my. A lot of my contemporaries. And. And we went on to form the Mars group at the University of Colorado. And everybody then went off into different aspects of space science. So it was really a seminal moment.

[B]

That's exciting.

[C]

It's worth pointing out that the Viking landers are about the size of a piano. In fact, like a piano, they are three legged landers. And that was to save mass in particular.

[A]

You mean like a grand piano?

[C]

Like it's like a baby grand piano? Yeah, yeah, exactly. You know, it's sort of triangular in shape, the platform. But the reason why the footpad was in the first picture was because we knew nothing about the surface of Mars, you know, about its strength. There was speculation that it could be very sandy and therefore one could sink into the sand. So it was important to sort of get a picture of the thing before it's. Before it disappeared in quicksands on Mars. And of course, what this picture also showed, because it was built up column by column of pixels, there was a sweeping of the scene in the early vertical columns. You could still see extra graininess. And that was from the dust settling from the landing. And then eventually the picture cleared up. So it's a very dynamic picture, both in terms of what you can see in it, but also for. For what it was supposed to capture. Possibly the demise of Viking.

[B]

It was. And just a quick note before we go to break. The lander had two cameras that look like a couple of coffee cans with a slit in the front with a tipping mirror. So these cameras worked in tandem, and these mirrors would scan up and down and up and down. And that's where you got that slow strip by strip image buildup, which, again, being a hopeless romantic here about it, actually kind of, again, added a sense of mystery and prolonged gratification, I guess you'd call it, as you watch these things come down. So it was just magical. All right, let's spirit our way into a break and we'll be right back. So stand by.

[C]

Hey, it's Ryan Reynolds here from Mint Mobile.

[A]

Now, I was looking for fun ways to tell you that Mint's offer of unlimited Premium Wireless for $15 a month is back.

[C]

So I thought it would be fun if we made $15 bills, but it

[A]

turns out that's very illegal. So there goes my big idea for the commercial.

[C]

Give it a [e-mail] switch upfront payment

[D]

of $45 for three months, $90 for six months, or $180 for a 12 month plan required $15 per month equivalent taxes and fees, extra initial plan term only greater than 50 gigabytes. Me slow when network is busy see terms.

[A]

Well, Pascal, Penny, you know, so it's been 50 years since Viking landed. By the way, it landed on the anniversary of the Apollo 11 moon landings. And as we're recording this, it's the anniversary of those astronauts return to Earth. So hopefully someone will be returning to Mars someday during the, the one of the next anniversaries for Viking.

[B]

It's only 10 years away and, and

[A]

yet, and yet we still had a story on, on space.com about how folks are still debating what Viking did or didn't find when it comes to life on Mars. And so I guess like the, the, as Rod mentioned earlier, there a lot of the experiments were aimed at like is, is there life on Mars? What is Viking gonna, gonna show us now that we get these, these kind of robot boots on the ground? And I'm just curious, like why are we still talking about it now 50 years later? Either it did or it didn't. Right, Right, Pascal? Right, Penny? Or, or is there more to it than that?

[D]

There's more to it. There's a lot more. Go ahead, Penny, let me hold forth and then I'll turn it over to you. Pascal? Yes, people are still wanting to relitigate the Viking experiments. I think in a way that's good because there was a very long hiatus in Mars missions after the Vikings. So we developed the capability to work the heck out of data and model things and try to feel our way forward without the infusion of new data and new experiments that we were all dying to have. And what it did was stimulate a whole lot of areas on Earth that we were studying that were germane to the life on Mars. I have a list of about 40 things that are important that we did not know when we designed the Vikings. Not only the lack of what we now rely on all the time, which is genetic analyses, right. DNA analysis and RNA analysis, but the deep sea hydrothermal vent organisms had not been published until 1979. Right. So the whole world of extremophiles on Earth was a very nascent study. We did not have a grasp, we did not know whether or not there was extant water on Mars really. And we didn't know that some organisms can live in rocks at a very, very, very low pace of life for very long periods of time. So our ignorance was profound. Should we have waited till we got smart to send such a mission? No, you cannot start Exploring when you know everything, because then you'll never know everything because you have to explore. And so they were a wonderful starter house, you know, for Martian exploration. And we learned many things from our ignorance and have built upon it. So there may still be data from the Vikings that we will be able to explain better when we do more exploration and more experimentation on Mars. So no data is really, truly dead. It can always be looked at.

[A]

Again, Pascal, I forgot to list the specific experiments on Viking as well. And as you know, as you kind of share your thoughts, can you kind of give us an idea of what, what were those experiments that we're still talking about today? Were they all the same? Were they different? Like, what were they trying to do?

[C]

Yeah. What was extraordinary about Viking and still is, is the boldness of the questions being asked. This is the first mission ever and still the only one so far that has ever gone to another planet to look for signs of life that's still alive today. It's not looking for fossils, it's not looking for bio signatures. It's looking for metabolism, the activity that's associated with life. And so there were three experiments, three key experiments on the biological theme. And they all involved scooping out, scooping up some dirt from the Martian surface with a robotic arm, which worked very well, and dumping that dirt into funnels that then led the dirt into a chamber. And so now you are in a confined and controlled environment on board the spacecraft in those little chambers. And what was essentially done was feeding the soil with stuff that we think life might want. And of course, there are some assumptions in there that it's somewhat Earth. Like one of the experiments actually was pretty clear, explicit about looking for Earth like life, because it was looking for photosynthetic microbes, microorganism that would actually draw energy from light. And just like cyanobacteria, which is one of the most primitive and common and widespread and long lasting forms of life on Earth, just like cyanobacteria, they would essentially eat light and released oxygen. So that first experiment called pyrolytic release was doing just that. It created an atmosphere in which the carbon, some carbon, was provided that was marked, it was radioactive carbon so that you track it, carbon 14. And then you would look at whether or not the soil would essentially absorb that and then release it as, as waste or output. The experiment was really interesting because the soil showed activity when it was sunlit, when there was a light on inside the chamber. So when there was light going on, the soil showed activity. It seemed like it was processing the radioactive carbon that it was fed, and the activity would go away if you heated the soil. You heated the soil, as in you would bake it so that you would kill anything that might be living in it. That activity ceased. So right there, the thinking was, wow, something seems to be behaving like photosynthetic life on Earth. But then the same experiment was carried out in darkness, and sure enough, the soil was still putting out stuff before it was heated. So it became clear that we were looking at something that was more chemistry about the soil, not biology. The other experiments were sort of on the same theme, but the one that remains very controversial, the thing that Penny was alluding to as being unresolved still today, is the label release experiment. That experiment involved feeding the soil with actually a liquid nutrient. And then you would track the. And some of it contained radioactive carbon again. And you would look at what would come out from that experiment. And what was noticed is that there was a positive response before you heated the sample. There's no light involved. Now you just feed the soil, and next thing you know, it's putting out gases. So the activity ceased if you heated the sample, which was, again, a very good sign that this might be life. But then that's all it did. So the PI of the experiment essentially concluded that, you know, this was, as far as he was concerned, a positive detection of life, of biological activity. He could not see, or did not want to see, that the activity could be due to just the soil chemistry, or at the very least, it could be either one still. So Gilbert Levine, who was the PI of the experiment, has maintained to this day that essentially his experiment detected life on Mars. So, of course, that's been very controversial. The other experiment, the third one, sort of had a similar. Was sort of a mix of the two previous ones. It involved providing nutrients as well and looking at the gases that were put out. But it too concluded that the soil was just behaving like it had some weird chemistry going on. And it's only in hindsight with Phoenix, which landed on Mars many years later in 2007, that it became clear that the Martian surface was not only very rich in all kinds of oxides, superoxides, but also in perchlorates. Perchlorates are super reactive chemically. They contain a lot of oxygen in them. And what you're essentially seeing on Mars is as if you were pouring hydrogen peroxide on a wound on your skin. You see fizzing going on, you see activity taking place, but it's not biology, it's Just the oxygen rich environment that's reacting with, with whatever you give it. So the results of the Viking experiments today, the general consensus, there are still some exceptions, but the general consensus is that we're looking at oxygen rich chemistry that's going on inside the soil.

[B]

All right, well, let's oxidize ourselves into a quick break and we'll be right back. So don't go anywhere. Introducing Meta glasses.

[A]

Hey Meta, any last minute tables for two tonight?

[D]

Sure, there's a great Italian restaurant 15 minutes away.

[C]

Hey Meta, where's the nearest flower shop?

[D]

Five minutes away, straight down Broadway, past the bodega there. Lilies are trending on Instagram.

[C]

Just saying.

[A]

Hey Meta, am I forgetting anything else?

[D]

How about setting a calendar reminder for next year?

[B]

Meta glasses available in more than 20 styles. So I've had the good fortune to have written a few chapters about Viking over my long and questionable authoring career. And there's a human story there as well. There are a number of people involved, of course, in life science experiments, but standing tall amongst them were Gilbert Levine, as Pascal's pointed out, and a gentleman Caltech named Norman Horowitz. Now, I can only say from a distance, because I never met either of these gentlemen, that Levine was very passionate about his experiment, maybe, maybe a little bit more than it warranted, but I could certainly understand that. Passionate that they may well have found microorganisms on Mars. Norm Horowitz went into this whole thing, from what I can tell by reading pretty extensive oral histories, thinking that there's no chance that we're going to find life on Mars or anywhere else off Earth. And that when we do, it's going to be so weird we'll never be able to figure out what the heck it is. So, you know, there's a bit of confirmation bias there on both sides, I guess. But as legend has it, it got to the point where Horowitz and Levine were pretty close to being at blows and almost were a couple of times over this whole thing because Levine wanted to continue looking at what he was looking at. And Horowitz was like, nah, nothing to see her move on. So, Penny, I understand you have some inside intel here.

[D]

Well, yeah, I mean, it was an interesting time and it did illustrate for me in my then youth how blind one could be enmeshed in your own expertise if you're unable to step out of that. And Norman Horowitz was a tall, large and imposing fellow, and I am a short person and I was very young at the time. And Norm went into it as you say, sure, that there was nothing there, and confident in the, as we now know, exceedingly primitive approaches that we had to looking for microorganisms. So he went to the Antarctic and used the kind of growth medium that I would try to bring up common soil microorganisms, or do a swab off your teeth and try to grow the organisms. And when nothing from that extreme environment grew in them, he concluded that there was nobody home. And then that was a lesson, I think, for all of us, that, you know, when you're trying to prove a negative, you're up against an insoluble problem. You can just keep working on something and bringing your, you know, your new ideas to bear. He cornered me at a Mars meeting at Caltech, and, you know, as a young budding astrobiologist at the time, and he basically told me that I should change my career path because everybody would always consider me a dilettante and not serious, and I would have no career and no future. And of course, I studiously ignored him in every possible way.

[B]

Well, good for you. How's that for support?

[D]

Yeah, I'm a cranky chick. Don't tell me what to do, you know? And secondly, I knew he was wrong. I knew he was wrong.

[B]

So at this point, I know that there was a couple of experiments, I think, didn't Chris McKay do one of them in the Atacama Desert, showing that you attempting to show that there might in fact have been a life science result with Levine's experiment? Do I have that right?

[D]

Yes, people have tried to reproduce it. You know, we can't guess at the lifestyle of organisms that may only be active for very short periods of time, every 10,000 years. We still would have a hard time with that. One of the great tragedies really, of the Viking mission was the descoping or removal of a fourth experiment in addition to the ones that did fly that Pascal so eloquently described. And this was called the Wolf Trap. And it was called the Wolf Trap because it was developed by a scientist named Wolf Vishniak, who had done a lot of work. He was a microbiologist, did a lot of work in the Antarctic. And his was a much more holistic, less reductionistic experiment using similar kinds of nutrient that were used in the other experiments, but introducing a sample into a chamber with the nutrient and then looking to see if that turbidity, if that medium became turbid or cloudy, if it became cloudy, then one could potentially infer that microorganisms were growing. This is a classic microbiological technique that we use on Earth. If it became cloudy to begin with, then you would just say, oh, it's suspended particles. And if that cloud then abated, you would have an abiotic signal. And for reasons of cost it was removed. It was the only experiment that really reproduced what we classically do microbiologically on Earth. And it's a pity that it was removed because it would have been a clear indicator if nobody actually grew in a classic biological way that we were looking at chemistry, but we were very much into reductionist chemistry based approaches. So I think that's a lesson for us now that we need to work both types of experiments as we go to other worlds.

[C]

I'm glad you brought up this fourth experiment. And, and it sort of goes to what essentially was inherently a fundamental limitation in Vikings approach, because even if there actually is life on Mars and part of what Vikings instruments saw was due to that life, I mean, you know, am I 100% sure that label release did not actually detect life? I'm not, I, you know, in my head it's, it's 90, 95%, but there's this lingering 2, 3% that hey, we're looking for something that's alien, possibly much weirder than we thought. I cannot rule it out. But this, at the same time it reminds me of what Carl used to say. Carl Sagan Extraordinary claims require extraordinary evidence. And so if the, if the claim is that Mars has life, you can't have something that is ambiguous even if it did detect life. You have to have something that's going to be overwhelmingly convincing you that. So to me we would know that we have found life on Mars. If somehow at least two out of the three Viking instruments, or if the wolf trap had flown, three out of the four had detected biological activity. At that point you would have some grounds for being able to claim, okay, we now have extraordinary evidence, it really could be life, but at this stage we don't. But having said that, I think that Viking sort of has opened the door to really how we should look for life on Mars. Penny mentioned a moment ago that we should go into caves to possibly find extant life on Mars. I think the search for extant life compared to fossil life or chemical biosignatures is so much more to the point and important for us. Even if Perseverance drove by a road cut and saw the fossilized bones of a bee sticking out of a rock face, sure, you'd write a paper in Nature and if they don't want it, you might Try a science. But the point is, you will not be 100% sure that you have found alien life. Mars and Earth are not isolated. We swap meteorites between these planets. And it's conceivable that life started on Mars and seeded the Earth with life. And we are Martians today on Earth. Or the reverse. And the point is, because planets are not isolated systems and swap meteorites, even if we found a fossil on Mars, it could still be some form of early Earth life that was sent back or shared between the Earth and Mars. We would not know 100% for sure that we found a real form of alien life, something that had its own origin, its separate biogenesis. And to. To ascertain that you found something that's really alien, you have to do genetics on it or you have to look at, you know, the amino acids that make up its proteins. Those would be able to tell you that whatever you found is not of the Earth. But to do genetics or protein analysis, you have to find these. These suckers, I was going to say. But the. These microbes, you have to find them alive. You have to therefore do something bold, like Viking did go and look for extant life.

[A]

Yeah, that's. You know, I think. Are we gonna. Can I ask my next question out Rod, or do we gotta.

[B]

Absolutely, yeah. Roll on. We're done with breaks.

[A]

I would, I would. I would point out, by the way, that if Perseverance drove by a road, cut and saw. Saw some kind of fossil, I would be like, who made that road? And I think that would be a big, A big, A big, A big discovery about extant life or not. But.

[B]

Tarek, excuse me just one quick second. I just want to let the audience know we've hit the hour mark in the show, so we understand if some of you have things you got to do. But we're now going into the bonus section because this is a very special broadcast going out on all our usual platforms, plus Space.com. so we hope you stay with us because we're going to run about another half hour.

[A]

Yeah, yeah.

[B]

All right. You're up, bud.

[A]

Well, yeah, and speaking about running and as Pascal mentioned, like, being bold again to look for life, I did want to ask Penny about your research with caves and extremophiles. And I guess what is it about caves, especially on Mars, that makes them a really great place to try to look for things. And if we were to send another Viking type mission that could somehow get into the caves, then, you know, how. How, I guess, how. What would you want on board what kind of experiments? Just another repeat of what, what Viking had or something more refined based on your research and what you know about what you can look for in caves on Earth.

[D]

Yeah, I mean, it would be a fabulous opportunity. Long been looking at the subsurface. So, you know, there's the relatively shallow subsurface that are represented by caves, and then there's the issue of deep drilling that would be, you know, delving into the deep subsurface. I think both are worth pursuing. And in fact, possibly you could have a better time, you know, taking drilling equipment into a cave that was already there because you are protected to a certain extent from the radiation environment of the planet. You know, 3 meters of basalt pretty much protects you. Yes, there are daughter products and so forth, and it's, and it's nuanced, but rock is a pretty good shield against some of the really difficult conditions that we face exploring. Either for robotics or even particularly for human explorers. Caves have been shown to potentially, even in the very thin atmosphere of Mars, that would appear to us to be a vacuum if we were measuring it here on Earth. They can retain ISIS modeling has shown. Kai Williams did a modeling effort in about 2010, 2012 that really showed that they can be very stable. We even see that on Earth. We have ice caves in New Mexico. Right. So there are ways for caves to protect against the overall environment. The second factor to think about is that, you know, we see the openings to caves and we think those are the ones that are there. But if you look at the subsurface cavities on Earth, we probably only have natural entrances into about 10% of them. So the amount of subsurface real estate that you have in closed caves on Earth is very high. We have reason to believe that that's probably the case for a lot of subsurface terrain on Mars, in which case these would be little oases potentially for a relic to biosphere. I think that it's unlikely that if Mars never gave rise to life that you would not be able to give rise to life in that highly distributed, very still harsh environment. But as a refugium, as a refuge for life as Mars became less habitable over time. So that's the rationale. The other rationale is that there's such diversity of caves on Earth in terms of average temperatures, geochemistry, the degree to which ice or water influences them, the exotic, in many cases, mix of gases that are in the caves, some are full of hydrogen sulfide, some are full of ammonia, some are full of weird aldehydes. And so forth. So it's a wonderful hunting ground for finding even more exotic extremophiles that we have no representatives on the surface. So it's helping us to build a field guide unknown organisms, and they will be in our back pocket as we go not only to Mars, but also to places like Titan, where any life there would have to be spectacularly different from life here. But it might respond to a lot of the same ecological demands, the quest for resources and how it would arrange itself in space in order to acquire that. So we're really sort of practicing and at the same time, of course, we're, we've been blowing open the envelope of what life can do here far beyond what just the palette of extreme environments on the surface are doing.

[B]

Pascal, you want to add something or shall we move on?

[C]

No, I mean, I love Penny's answer. It's very thought provoking. I was just thinking also about Tariq's question. You know, I would like to see an experiment that would go into some of these caves on Mars. We know of more than 1,000 pits and caves on Mars today in terms of just mapping out entrances to depressions. And one of the experiments I would like to see happen would be to essentially scrape the walls of these caves and then analyze anything that might be proteins. And if you could identify what makes up these proteins, and you can do this with a chemistry kit. If we look at, if there are proteins associated with life, are those proteins made of the same amino acids as the one used by all life on Earth? All life on Earth, with no exception, uses a collection of about 20 to 22 of the same amino acids among thousands possible in nature. And not only do we just use these 20 to 22, but we only use the left handed version of these amino acids to make up the protein molecule. These amino acids are molecules that sort of exist in nature in one form, but also in the mirror image form as well in terms of their geometry. Earth life uses only the left handed version of these amino acids. And so you could just find some protein on Mars and realize that it is actually using only right handed, for example, or different set of amino acids, not the same 20 to 22 that the Earth life uses, but a different one. A bingo. You have, you have found a biosignature that is unquestionably alien life. Alien life.

[B]

So that would take the panspermia conversation off the table, I guess, about whether or not life had commuted from Mars to Earth. Earth to Mars. But I, I want to ask both of you we had some recent results from the Perseverance rover that were kind of promising. I think it was about the same time the drill got stuck in that rock, if I remember right, about complex organics that they found. And unfortunately, it doesn't carry anything that can immediately define life, such as it is. And then years back with the Spirit rover, the Myrrh, we had what looked like to some people a photograph of what could have been fossilized algal mats, but that one went kind of quiet quickly. And then the Perseverance story got a little more traction, but that kind of faded out as well. Any opinions on that?

[D]

Not enough data.

[C]

That's really it, right? I mean, I can say a few things, but do you want to respond to this, Penny?

[D]

Well, it's so tantalizing. Of course we want to go and follow up on it. But what it shows us is that maybe it's time to be a bit more bold again in the Viking style. Not to criticize the wonderful experiments that are on those devices, but how long will we be doing those analyses without adding something that could be a bit more definitive? I think that's important for us, both inside of NASA and elsewhere, to think as we're contemplating future missions, can we add the capability to actually take a result like those and really work it in situ? Do we have to wait for astronauts to be there on the surface? I think for some things it would be easier, although getting astronauts there is not easy. But I think there's still a lot of scope that we have in the robotic realm in order to be able to interrogate those. Would I make conclusions about those now? No, I think that the presence of tantalizing microbial looking patterns in and on rocks should not be dismissed. They can sometimes be mimicked by abiotic processes, but very often on Earth, they're microbial. So I think that's something to pursue in the future. The reason it went quiet after that original claim was because you kind of need to do a lot of work, probably in situ, in order to really vet whether something is of microbial origin, maybe even molecular fossils. So limpids tend to hang around in rocks and things like that.

[A]

You know, one thing that we haven't talked about when it comes to Viking, and I guess for all Mars missions, or even if, let's say we have a Viking, we can't say Viking 2, because there was a Viking 2, but like a 2.0, that is all life detection all the time. Although I think Rosalind Franklin is going to have some life detection on it. When, when ExoMars gets there is, is the idea of ensuring that what we detect, if anything on Mars we didn't bring with us, you know, in terms of planetary protection and then even, you know, protecting any samples we bring back to Earth. And I'm, I'm curious how, what is the word fidelity, how, how clean Viking 1 and Viking 2 were when they landed so that we could be absolutely sure if they found anything that it came from Mars and how important that is for any mission that comes forward after that.

[C]

Yeah. Should I jump in?

[D]

Yeah, go ahead, sure.

[C]

So Viking 1 and 2 landers were on record, on record as being the cleanest spacecraft ever launched. They have been, they were, quote, sterilized at great cost, although they actually were not sterilized like one would understand. Medical instruments, for example, are sterilized, but

[B]

they're still the gold standard.

[A]

How do you boil a piano sized lander right in water?

[B]

But they bake it at 300 degrees. It's just, you can't do that with things like rovers. They're a lot more delicate.

[C]

Yeah, they bake it, they irradiate it with ultraviolet light. It has been close to being sterilized, but not fully. And so any one of these missions that we send to Mars arrives on Mars with some complement of microbial life that's clinging on to dear life on these sheltered parts and nooks and crannies of the landers or the rovers. The general thinking is that if all life on Earth needs liquid water to metabolize and thrive. And so these microbes that are from the Earth that we might have brought from Mars inadvertently to Mars inadvertently, are believed to be in stasis. So they're not going to be proliferating unless they somehow came in contact with liquid water. And so far there's no chance of that having happened. And you brought up planetary protection, which is sort of an essential thing in all of this. And it works both ways. You, you want to protect the planet that you're exploring so that you don't find Earth life inadvertently that you've brought yourself and call it Mars life. But you also want to protect your crew members, in the case of astronauts from encountering Mars life and becoming contaminated by it and potentially sick. I had a chance to. Penny is the second director of the NASA Astrobiology Institute chronologically. But the first director of the NASA Astrobiology Institute was Barry Bloomberg. He had won the Nobel Prize in Medicine for the discovery of the hepatitis B virus. And he came up to the Arctic to our project on Devon Island. Many years ago. And one day I had this incredible opportunity to have an evening chat with him about the possibility of life on Mars. And you know, I was asking him, you know, let's say we found a virus on Mars, should we really worry about the possibility that it would harm us? Aren't viruses supposed to be tailored to their hosts to do something bad to the host? You know, wouldn't a virus somehow be otherwise innocuous to us? And his answer was no. He could imagine viruses that might do nothing to us, but also viruses that could kill all of life on Earth. And so right there, the planetary protection thing is a real thing. And since we're going into the unknown, we don't know what we might find, we're going to have to have protocols that are very strictly adhered to in order to explore Mars with humans. And in the meantime, if we're looking for life with robotic means, we're going to have to have clever ways of making sure we don't disturb what we are looking at.

[B]

So, Penny, given all this, both the concerns about protecting Earth if we're bringing something back, and the percentages of where you sample the dirt, what are your thoughts on how important Mars sample return is? I mean, obviously you just don't want to settle down in the most part sterile part of the planet and grab some dirt and cross your fingers and hope. How do you handle that and how important is it?

[D]

Well, you know, the future of Mars sample return is up in the air. As you probably know. It's a very tough call. If I were going to pick the most likely to be life bearing sites on Mars, it would not be where we collected the samples. But that wasn't the point of this mission. It was, you know, intended to do the best that it could at the landing site that was selected. And I believe that we have a great deal of energy invested in this, money and human capital invested in this. And I think it's a pity if we don't find some way to get those samples back. I know that there, you know, there are arguments on both sides of whether or not we should do that or whether we should just spend our resources, you know, pushing forward to get humans there. But frankly, I've been in many life threatening situations in extreme environments on Earth with a lot more knowledge in my back pocket before I went there than we currently have about the materials that we would find on Mars. So I think that, you know, knowledge is essential before we commit astronauts to going there. And Mars sample return is what we have available to us right now. So I'm pretty interested in seeing us, you know, find a way to go get those samples. Do I think, you know, green giraffes are going to jump out of the tube? I do not. But I think just even in terms of astronaut health and safety, you know, for the purposes of exploration, that we need to see, plus we would do a whole lot of science, maybe not astrobiology, but certainly in terms of the geological surface.

[C]

Yeah. I mean, one thing that's worth adding as well is that Perseverance and curiosity have now both found a number of complex organic molecules, meaning molecules that contain carbon but also nitrogen, hydrogen, oxygen, that on Earth are sometimes associated with biological activity. But in the general case, and no exception so far, they are also possible in the context of non biological and therefore strictly geological activity. So from the standpoint of the chemical stuff that's been found, it's been, you know, not worth bringing back, so to speak. On the other hand, I mean, if you're focused on biology and the sexual life for geological reasons, there are plenty of reasons to bring those stuff back, those things back. Now, having said that, Perseverance did run into a rock which it has sampled called Cherjeva Falls Rock. CFR and CFR contains these little weird leopard spots they're called, you know, along a bit of a vein across this rock. And so far these leopard spots are the most tantalizing sign of potential life ever found on Mars. They were sampled, they have been collected. These leopard spots are made of two particular two weird minerals, vivianite and grigite. For those of you who are geologists, they too can be found in biological contexts and geological ones. But the geological context is very rare and extreme. The biological context is where these two minerals are most commonly found. And the geological extreme context where they can be found as well, are not apparently what this rock was sort of evolved from, derived from. So I think we have sitting in the Perseverances collection right now possibly one of the best indicators of potential, you know, biology found on Mars. But I'm still struggling with finding this worth spending 7 to 11 billion dollars to bring samples back from Mars because we're still not going to be able to tell whether this is alien life or not. In other words, the result, separate origin of life.

[B]

We share your concerns, but as Tarek recently pointed out to me, you could probably load, I don't know, what do we figure, maybe 30 Viking Lander Orbiter

[A]

combos, 50 Starship 51.4 if star. Oh yeah, 51.4. Because Starship can carry 100 tons, allegedly. And the total launch mass of Viking and its orbiter. Okay, Professor, 77,000.

[B]

Yeah, I was more a fan of sending up lead rovers, but. But I take your meaning. But of course, Starship has to work for us to do that. Well, I want to thank everybody, especially you two, Penny and Pascal, for joining us today for episode 220 that we like to call first on Mars. And thanks to our new audience over on Space.com for joining us today. We appreciate you sticking with us for a long episode, but it was an important one. And when you've got guests like this, you just have to roll along. Penny, where can we keep track of your work online?

[D]

Well, you know, I work at NASA. I'm a busy civil servant working on a whole lot of projects, not just astrobiology. So the NASA websites are the place. And I also do a lot of public outreach, so I often give talks both online and in person.

[B]

Fabulous. And where are you based, by the way?

[D]

I'm badged to NASA Ames Research Center. Okay. I'm on permanent remote detail to Kirtland Air Force Base in Albuquerque, New Mexico. Closer to the caves.

[B]

You know, if you're able to keep your badge more than three months after you haven't actually set foot in that location, you must be very important, because for. For those of us normal NASA contract employees, the second you've been out of there for a number of weeks, they're like, thanks for coming back. Give me your badge. Pascal, where can we keep track of what you're up to online? And your artwork, by the way?

[C]

Yeah, so SETI Institute. Mars Institute. And for my artwork. Yeah, for those of who are interested, I paint about the human exploration of Mars, mostly. So that'[e-mail].

[B]

or you can come to my place and see the painting I have hanging next to my stairway. Thank you for that, Pascal. Tarik, where's the best place to spy you laughing your three heads off?

[A]

Well, you can find [e-mail], as always, on the socials. Tarikjmalik. Tonight you'll find me glued to my computer, monitoring the SpaceX Starship Flight 13 launch. And if you like video games, you can find me on YouTube @spacetronplays. That's always great, but mostly all the space stuff.

[B]

My, but will we see you watching a launch or a scrub?

[A]

Well, let's hope. Let's hope for launch. Man, I got a weekend to plan.

[B]

Yeah, and we got to get this thing rolling so we can land people on the moon finally. Remember, you can always find me at pilebooks.com [e-mail] and you could drop us a line at Twistwit TV. We do welcome your comments, suggestions, ideas, even compliments, as rare as they are. And your space jokes, because you heard the ones I used today. If you could do better than that, send them along. New episodes of this podcast publish every Friday. And your favorite podcaster, so make sure to subscribe. Tell your friends, give us reviews. We'll, we'll take whatever monetary denomination you use for giving thumbs up or smiles or whatever, whatever commerce they use. You can also follow the twittech Podcast network at Twit on Twitter and on Facebook and Twit TV on Instagram. Everybody, thank you very much. Thank you, Penny. Thank you, Pascal. Really appreciate you coming in. Thank you.

[A]

Thank you all.

[C]

Thank you.

[B]

And we'll do this again. Take.