Planetary Radio: Space Exploration, Astronomy and Science - Life on Mars...and Earth

Episode Date: April 5, 2004

We visit Harvard biologist Andrew Knoll for a conversation about finding life on the red planet. Emily Lakdawalla is seeing red on another of Earth's neighbors, and Bruce Betts spins a tale of Death Stars, cockroaches and trivia contests on What's Up!Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

How will we recognize life on Mars? Find out on Planetary Radio. Hello everyone and welcome back. I'm Matt Kaplan. Biologist Andy Knoll of Harvard is our guest this week. Stay with us for a fascinating conversation about life on one planet we know well and another where mysteries are beginning to unfold. Bruce Betts manages to fit cockroaches, the Death Star,

and our new trivia contest into What's Up. First, though, Emily wonders if there could be another red planet in our solar system. I'll be right back. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, Everyone knows that Mars is red, but what color is the surface of Venus? You'd think that there would be a simple answer to this question, but there isn't. The answer to this question depends on what you mean by color. Whether color is an intrinsic property of the surface,

or whether you mean the color you would see if you were actually standing on the surface of Venus and looking around. The intrinsic color of the rocks on the surface of Venus that were photographed by the Soviet Venera spacecraft is a uniform dark gray. That is, the rocks reflect short wavelength, or blue light, just about as strongly as they reflect long wavelength, or red light. But you wouldn't see this gray color if you were actually standing on Venus. Why not? Stay tuned to Planetary Radio to find out. Dr. Andrew Knoll holds the Fisher Chair in Natural History at Harvard University, where he also serves as Associate Dean of the Faculty of Arts and Sciences.

Paleobiologist, microbiologist, astrobiologist, these titles and others all fit him well. His current work on the Mars Exploration Rover science team has kept him in Southern California for much of the last few months. He had just returned to Pasadena from Massachusetts when he invited us up for a conversation. Andy, first off, thanks very much for inviting us up to your home during your stay here in Pasadena. Well, it's a pleasure to talk with you. Now, I don't know whether this is your home away from home

or JPL is more your home away from home because you're spending a lot of time there. Well, it's fair to say I sleep here and much of my waking time is spent at JPL these days. Just before we started to record, I was thinking of you as an astrobiologist, but you said that this interest in the astro side of things kind of came a little later for you. Well, that's true. I've always been interested in the earth,

and I've always been interested in biology, which has led to a career in trying to understand how earth and life are related to one another. And I suppose at some point you have to start asking about a second example of all this. And the opportunity to work on a Mars mission was just too good to resist. Is there a difference between a biologist and an astrobiologist? Well, I think cynics would say that biologists are people who have subject matter and astrobiologists are readers of fiction. So far. Well, that's right, but the whole excitement about this Mars program and other programs that are on the books is that one doesn't have to spend the next decade or two simply speculating about life beyond the Earth. For once, we're actually

having a program of exploration, which will allow us to put some factual constraints on the issue. We very much want to talk about life on this planet, the one planet where we know it exists, but let's talk about what's happening on Mars. We have spent a great deal of time on this show, right up through last week's program, with one exciting announcement after another. I would have to think that for a biologist, astro or otherwise,

the announcement of conclusive evidence on Mars of a salty sea had to have you dancing in the aisles. Well, everything we've learned about Meridiani Planum has been exciting. And as you say, the characterization of this area that we're getting is a place that was wet. It was acidic. It allowed some oddball salts and iron minerals to deposit. But the exciting thing for me is that for the last couple of years, I've actually worked at a place on this planet, on the Earth, that deposits a similar suite of minerals. And there are microorganisms all over the place in that

environment. Now, that doesn't mean that they will necessarily have left a record on Mars, but it does say that what we've learned on Mars makes one eager to have more rigorous and specific astrobiological exploration. When you talk about a similar environment, you're talking about, I think at least in part, the kinds of iron compounds which got us to go to Meridiani Planum in the first place, right? The hematite. That's right. I mean, the wonderful thing about this mission is that Meridiani Planum was flagged for its interest on the basis of orbital observations, which included a widespread, and by widespread I mean spread over an area perhaps the size of Oklahoma,

a widespread signature of the iron mineral hematite. Now, that's what got us to Meridiani, but what we found is a much more complex sedimentary geology with sediments that include a lot of salts laid down, at least in part, in water over a wide area. And iron is just part of this mix. And the suite of physical and chemical signatures we've seen so far really makes a coherent picture of at least what one environment was like at one point in the history of our neighbor. What you've found is in your work here on this planet, that this is an environment which can be quite hospitable to life? Yes, and it's an interesting story. One of the minerals that's

been found on Mars is a iron sulfate mineral called jarosite that forms only in strongly acetic waters, that is at a pH of three or less. Now, Jarosite is found in a number of places on Earth. One of the most interesting places is along the Rio Tinto in southwestern Spain. Rio Tinto means Red River in Spanish, and it comes by the name honestly because the water is the color of rubies. It comes by the name, honestly, because the water is the color of rubies. And the water is the color of rubies because under the strongly acetic conditions of the groundwaters there, oxidized iron remains in solution. And so it gives rise to the thought that if we had been around Meridiani Planum three or four billion years ago, the water that we might have seen covering this vast lake or sea might well have been fire engine red. Wow.

That's dramatic. Well, it is. And the nice thing about the Rio Tinto, well, there's two nice things about it. One, from a biological perspective, all sorts of organisms are able to live under these very acidic conditions. Most of them are microorganisms, and they live there by using a pretty interesting trick. That is, they haven't learned how to do their biochemistry at pH 1. What they've learned to do is to shield their cytoplasm,

the interior of the cell, from that exterior acidic environment. So they're happily doing their biochemistry at the same pH as you and I are. They simply learned this trick to do it. The consequence of that, of course, is that while these organisms have been able to learn to live in these environments, it's not the type of environment where early life would have or perhaps could have got going. of environment where early life would have or perhaps could have got going. That's exactly where I wanted to go, because it didn't sound like a place where you would have expected life to be generated, where life could evolve from scratch, if you will. Well, that's right. And if one asks the next question, that is, whether or not life can live in an unusual

environment, and we know on Earth that within certain limits, organisms have learned to live at many extremes of hot, cold, acid, basic, you name it. Life couldn't have started in all of these environments. What happens to many of the standard chemical reactions that a lot of people at least think might have been important in the genesis of life on this planet? The answer is that a lot of them don't work very well. Huh. Where does that leave us as we continue to consider Mars as a place where life once existed? And what should we be looking for? We heard from Ken Herkenhoff, we have heard from Steve Squires, that the Mars Exploration Rovers simply may not be equipped to look for this evidence. They weren't designed for that. They were designed to do exactly what

they've been doing for the last three months. That's right. These rovers were designed to give us information on the environmental history of the Martian surface. They've done that beautifully well. There are a few signatures of life that might actually be visible to the pan camera. That is, there are certain large-scale features that can be imparted to accumulating sediments by microbial communities. And at Rio Tinto, we actually see ancient iron deposits that allow us to see how biology leaves an imprint in these rocks. We haven't seen any of those, although we in principle could if they were there. But I think to really ask deeper questions about biology,

we are going to need a different kind of mission, and at the end of the day, very likely a mission that brings samples back to Earth. Which is something that you've worked on, I know, and maybe something that we can pick up with after we take a quick break. Our guest this week is Andy Knoll. He's Fisher Professor of Natural History at Harvard University and a member of the science team back in town this week is Andy Knoll. He's Fisher Professor of Natural History at Harvard University and a member of the science team back in town this week for the Mars Exploration Rover missions.

And we'll be back with him in just a moment. This is Buzz Aldrin. When I walked on the moon, I knew it was just the beginning of humankind's great adventure in the solar system. That's why I'm a member of the Planetary Society, the world's largest space interest group. The Planetary Society is helping to explore Mars. We're tracking near-Earth asteroids and comets.

We sponsor the search for life on other worlds, and we're building the first-ever solar sail. You can learn about these adventures and exciting new discoveries from space exploration in The Planetary Report. The Planetary Report is the Society's full-color magazine. It's just one of many member benefits. You can learn more by calling 1-877-PLANETS.

That's toll-free, 1-877-752-6387. And you can catch up on space exploration news and developments at our exciting and informative website, PlanetarySociety.org. The Planetary Society, exploring new worlds. Planetary Radio returns with our guest this week. He is Andy Knoll, Fisher Professor of Natural History at Harvard University. Out in Pasadena once again as a member of the science team for the Mars Exploration Rovers. University. Out in Pasadena, once again, is a member of the science team for the Mars Exploration Rovers. Andy, when we stopped, we were talking about the Meridiani Planum and its possible

similarity to this, the Rio Tinto, I think you called it, this area on Earth that you have studied. We were talking about there might be some gross evidence that would be visible from the pan cam on the Mars Exploration Rovers. We have heard, though, that fossil evidence might be too small for the instrumentation on the rovers to see, specifically the microscopic imager. Right, that's correct. The microscopic imager is a wonderful instrument. It's enabled us to see details of the Martian rocks that are, to me, really astounding. On the other hand, it's not a miracle machine.

It has size limits of what it can observe. And to find fossils of microorganisms, we would need at least an order of magnitude, more magnification to see them. So very likely in 2009 there will be much more heft to the microscopic imaging capability, but ultimately we will want to bring these rocks back to our labs and prepare them so they can be looked at with really high-power microscopes. I know that you've done work on a sample return mission, which at one time we thought might happen a little bit sooner than it's now projected to take place. Well, that's right.

You may remember that the mission we're in at the moment began life as a 2001 sample return mission. I think what it evolved into is probably the right mission for right now. But we do have to see this as a stepping stone. And it will lead to more sophisticated robotic missions beginning in, well, in 2009, there will be a sophisticated rover. And then sometime in the decade after that, we do hope to have samples returned to Earth. Really, when you talk about either of these missions, the 2009 mission that's prepared to look for this evidence on in situ or the sample return mission, is it a safe bet that we would know we were looking at evidence of life if we found it

and it did have a separate genesis from what we're used to here on planet earth well there's a couple of good questions there the first one is i think there are ways that we can be sure we're looking at evidence of biology and and one way to think about it is as follows and and this will show that I, as a kid, grew up with the so-called new math, so I tend to think in terms of Venn diagrams. But if you think about all of the patterns, either chemical or physical, that can be made by known biological processes, and then think about all the patterns, chemical or physical, that could be made simply by physics and chemistry without intervention of biology.

What you'll find is that you can think of each of those as being a circle, if you will, and the circles overlap. So if you find a sphere five microns in diameter, well, there are five micron in diameter spherical bacteria. On the other hand, there are lots of ways to make five micron spheres without invoking biology. So if you find that on Mars, the question marks remain. On the other hand, to take a chemical example, one of the biological materials that you make and I make and a lot of other organisms make is cholesterol. We have no evidence that physics

and chemistry will make cholesterol in the absence of biological enzymes. So therefore, if we find cholesterol on Mars, I'm willing to agree that life was there. The bottom line here is that because we don't have any assurance that life on Mars, if it ever existed, would have the same characteristics as the terrestrial life that we're familiar with, we have to use the capabilities of physical chemical processes as our yardstick. And something becomes interesting as evidence of biology when we can't explain it by known physical chemical processes. This makes me think of a certain infamous meteorite that people are still arguing about,

I think. They are. I think the arguments have toned down because there's been a lot more careful work by people on all sides of the question. And while good friends can disagree on this, I think at this point, we don't have any strong evidence that there is any feature in those rocks that cannot be explained by physical chemical processes known to have influenced the rock. Extraordinary claims require extraordinary proof, said one of our founders. We talked a little bit about in the first part of our conversation about this question of an alternative genesis, the genesis of life on Earth as opposed to Mars.

I had the impression that maybe there was more that you could say about that. As we look at this not the friendliest environment that we've found so far on the red planet and this possibly red sea as you've described it. Well, there are certainly lots of things you can say. In fact, you can probably say almost anything you want because we have no evidence one way or another. On the other hand, just finding fossils, which would be extraordinary if it were ever to occur, but it is likely that simply finding the shapes of ancient bacteria on Mars would not tell us whether they were the progenitors of earthly life or they had a completely different

origin, because I would guess that wherever they might exist in the universe, bacteria are going to be small. They're going to be spherical. They're going to be rod-shaped. There are good physical reasons for that kind of shape variation, and it's likely to characterize biology over a wide range of systems. systems. On the other hand, when we get back to this question of how does life originate on a planet that's dominated by sulfuric acid rather than carbon dioxide, we don't know the answer to that question because no self-respecting professor would allow his or her graduate student to do these kind of experiments because they're pretty much irrelevant to Earth. But the few experiments that have been done do suggest to us that if these kinds of conditions were prevalent on early Mars, and there's some uncertainty about that, but if they were,

then one might guess that the road to biology on that planet might have been somewhat different than the road to biology on Earth. I have rarely been sorrier to say that we are almost out of time. And we started by talking about the fact that you came to this consideration of astrobiology later than some people, because you're very much a biologist, a natural scientist of this planet, You're very much a biologist, a natural scientist of this planet, who cares a great deal about diversity and the crisis that diversity of life on this planet faces. How do you tie the two of these together, a planet that still is overflowing with abundant diversity of life and one that may not have had any at all? Well, I think it is interesting, at least, that we stand on the verge of discovering something about life on other planets at the exact same time that we stand on the verge

of losing a substantial portion of the diversity on our own planet. My perspective on biology that comes from my work in paleontology over the years is that the biological diversity that we see around us today is the legacy of four billion years of evolution on this planet. And I think we jeopardize that diversity at our peril. Not only do we, I think, as the dominant organisms on this planet now, have a responsibility to stewardship, but it may well be that losing key types of diversity on this planet will actually place us in some jeopardy. So I don't know that we can tie the questions of Mars and the worries on Earth

together too much, but I think that as we do justifiably generate and maintain our excitement about the search for biology in the universe, we should also register our concern and do whatever work we can to ensure that our grandchildren will know about rhinoceroses from more than picture books and coral reefs from more than films. Last question. Does our fledgling exploration of Mars suggest to you that we may have a chance to show that we can be a better caretaker there or the kind of caretaker there that we should be more of here? Well, I don't know what the future holds for Mars, but I would extend this concept of stewardship to include Mars so that whatever the future human presence on Mars may be, I hope that we will take care to recognize that we have come upon a pristine planet and that I hope we will do whatever we can to maintain Mars as a pristine place in the solar system.

That sounds like a good place for us to wrap up. It has been an absolute delight speaking to you, and I very much look forward to having you back on the program. Great, thanks. Andy Knoll is Fisher Professor of Natural History at Harvard University, a chair that has been in existence, he told me, for

what, well over 200 years now, I suppose, and is in Pasadena as a member of the science team for the Mars Exploration Rovers, which continue to make incredible discoveries and probably will be doing so for some time to come. I'll be back with Bruce Betts right after this from Emily. I'm Emily Lakdawalla, back with Q&A.

Although the rocks on Venus are dark gray, that's not what you would see if you could visit there. That's because the light on the surface of Venus has a very strong red tint to it. This is caused by the same phenomenon, known as Rayleigh scattering, that gives our sky on Earth its blue color. On Venus, any light that makes it to the

surface has come through a planet-wide cloud cover and an atmosphere 90 times as thick as Earth's. On Venus, Rayleigh scattering effectively removes all of the blue light, creating a planet-wide red light district. So if you were standing on the surface of Venus in a protective suit that kept you from the noxious atmosphere, crushing pressure, and searing heat, you'd be seeing red. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. Bruce Betts is on the phone.

He is the director of projects for the Planetary Society. Must mean that it's time for What's Up. Hi, Bruce. Hi, Matt. What's up this week? Well, we've got our friends the planets in the night sky. Go see them. Can't miss them.

Venus really, really bright in the west after sunset. And also after sunset, look above to the left, you'll see the much dimmer Mars continuing to line up in the sky, roughly overhead after sunset. Saturn continuing even farther, and you will see Jupiter extremely bright. Venus is playing in one of your favorite constellations, Matt, your favorite constellation, the Pleiades. Oh, yes. Well, it's not my favorite.

Orion's my favorite, but you're close. Okay, and we're close in the sky. But it's playing in the Pleiades? The seven sisters. Now, there's actually a weird effect that you can see this week, mostly on April 7th, where you actually get some lensing through the Venus atmosphere. So you end up seeing what looks like instead of seven sisters, if you have a clear view, you might see eight sisters. Oh, how cool.

Now, this is not relativity-based gravitational lensing here. No such luck. No, not enough gravity for that. It's a funkier atmospheric thing. Okay. All right. How about on to this week in space history? Yeah, let's do it.

This one amused me. On April 8, 1999, astronaut Janet Kavandi, while demonstrating a physics experiment, one of those made for kids, actually caught a hockey puck in her mouth while on board the space ship. Well, there are NHL players who do that almost every week. Yeah, it's true, and she didn't even break a tooth. Boy, that's historical. On to what?

Random space facts! Cockroaches. Did you know, Matt, that cockroaches have been exposed to the environment of space for nearly 500 days and survived? What? Who are you kidding here? Are you talking vacuum? I'm talking vacuum. Grown-up cockroaches. Yeah. Yeah, I mean, they had to provide them with food, but the actual environment.

They could eat? They had nothing to breathe, but they could eat? They're funky things. I don't... I just report them like I read them. This is not your April Fool's presentation, is it? April Fool's! Oh, shoot! He got me! He got me! Nothing I've said since the beginning except planets are in the sky was actually real. Nothing I've said since the beginning except planets are in the sky was actually real. So don't go looking for the eighth sister in the Pleiades.

I apologize to my friend Janet Cavani and the cockroach. You got me on the cockroaches thing. I thought I could hold you on that. I was totally taken in. I should have caught you on the Venus atmosphere thing because it it's pretty much opaque, and it doesn't extend out very far. So, God, I was totally taken in by that. But the cockroaches, no. I don't think they could last more than a couple of days in vacuum. Last year we conspired on April Fool's show.

This year I just decided to go solo. Oh, well done. On to the much more serious trivia part of our show. Last week we asked you in utter sincerity, which moon in the solar system, which satellite orbiting a planet, looks most like the Death Star from Star Wars? The answer, very clear, Mimas. How do people do?

And that's one of Saturn's moons, right? Yes, it is. Well, here's our winner, and then I'm going to mention a couple of others as well because they had interesting things to say. Our winner is Ross Koger, Koger or Kojer, I'm not sure which, of Melbourne, Australia. And boy, do we have a lot of listeners down under.

Ross actually gave us three separate possible answers. One of them was indeed Mimas, and for that he will be getting the Planetary Radio t-shirt this week, Bruce. Yay! I got a couple of other interesting ones, though. By the way, Mimas, the clear, making it look so much like the Death Star is a very large traitor on one side of the...

Okay, please continue. And so it looks like that big dimple in the Death Star, right? Yeah. Did you know, Matt, that although Star Wars was filmed before Mimas was actually imaged by Voyager, when they did Return of the Jedi and kind of had that returning Death Star, they do a brief segment where they actually throw in a picture of Mimas. I didn't know that. Yeah, that's another April Fool's joke. Oh, good trick.

Go ahead. What else did people think? But George Lucas must have been psychic because it is a pretty strong resemblance. Scott Borgsmiller, one of our regulars, got it right, but he also said that if you're looking for the dark side of the force, you should look for another moon of Saturn, Iapetus, because it's dark on one side and light on the other. Darth, Darth, back in the closet. Darth Vader breathing there in the background.

And then we have some recent winners. Darth, Darth, back in the closet. Darth Vader breathing there in the background. And then we have some recent winners. Didn't win this week, but Karen and Ben wrote in, and they got this little thing, which I guess I'll read. Of course, both the Death Stars are now destroyed, a long, long time ago or so the story goes. Therefore, we suppose the rings of Saturn are closer to what any Death Star might look like right now, should they ever have existed.

But our answer is still minus. When Cassini arrives in July, closer to what any Death Star might look like right now, should they ever have existed. But our answer is still minus. When Cassini arrives in July, perhaps it will reveal that the rings of Saturn are comprised of all those poor stormtroopers that got blown up in Star Wars and Return of the Jedi. Which means that there may be Ewoks on Saturn, they point out. This would explain a lot. What's our question for this week?

Our question for this week, Matt, inspired by you. To the nearest thousands of degrees, thousands of degrees, what's the surface temperature of the sun in Celsius? In Celsius. Thank you very much. The surface temperature of the sun, how do they enter? Go to planetary.org slash radio.

Follow the instructions. Win your Planetary Radio t-shirt. Good times. It's a great shirt, too. Bruce, I think we're done. We are indeed. Thank you, Matt. Everybody look up in the night sky and think about radius of curvature.

And don't pay any attention to Bruce. Thank you, and good night. That's all the time we have for this edition of our show. Join us again next time as we continue our adventure in the cosmos. Have a great week.