What Would a Martian Drive?
Chartered to study how best to set priorities for the next moon and Mars initiative a newly-formed Presidential Commission -- including four prominent scientists -- held its first public forum and announced its nine commissioners. One task for the blue-ribbon panel, chaired by Defense veteran, Pete Aldridge, is to sustain a space exploration goal for several generations.
The following session is the first installment of a question and answer session between leading space scientists and the commissioners, including Neil Tyson, Director of the Hayden Planetarium and Carly Fiorina, CEO of Hewlett-Packard. Dr. Jonathan I. Lunine is professor of planetary science and physics and the chair of the theoretical astrophysics program at the University of Arizona. Dr. Michael Carr is an astrogeologist in with the U.S. Geological Survey in Menlo Park, California. David Morrison is a senior scientist at the NASA Astrobiology Institute.
edited Q & A session with David Morrison, Jonathan Lunine and Michael Carr: Part I
Maria Zuber: There has been a lot of discussion on the Commission whether or not the search for life should be the central scientific tenet for exploration. There's a lot of interesting things to explore that don't involve life. Suppose we look more closely at Mars and we don't find life, does that cut off planetary exploration? Could each of you comment on how the search for life fits into a broader scheme of exploration, and whether or not that search should be the driving factor in the scientific aspect of the exploration.
David Morrison: My own belief is that life is the most important organizing principle, although not the only one. But I said life, not just the search for life. It really takes two elements. For the scientist and indeed for the public also, finding evidence of life on another world and comparing that with the life on our own is basic. But the other basic thing is the moving of our life from its home planet to other worlds; the expansion of terrestrial life into the solar system. I think that's equally important.
Michael Carr: With respect to Mars, I do believe that life is what is driving and what should drive the program in its early years. I am not a biologist; I'm a geologist. I'm interested in how different planets work. I'm interested in the planet's interior and the planet's geological history, but I just don't see that as strong a rationale as the life issue, which is very real for Mars.
|Jonathan Lunine of the Lunar and Planetary Laboratory at the University of Arizona
Image Credit: space.com
Jonathan Lunine: From my point of view, if you look at human cultures throughout history, every human culture has a set of stories that essentially addresses the question of their role and humans' role in the cosmos. And so I would see life as an organizing factor, or an organizing motivator, I should say, in exploration. But in the broader sense, we all want to know what our place is in the universe, how the universe came to be, and how planets came to be, and then how life came to be. And by natural extension, whether we are something that is extraordinarily rare or unique, an intelligent species on a habitable planet, or whether we are a very common outcome of the evolution of the universe. So it isn't just the search for other life on a planet in our solar system, or another planet that is like the Earth orbiting around another star. It is the understanding of our place within the universe and whether we represent a singular or a common phenomenon.
Paul Spudis: One thing that we have found out in the past 20 years of exploration is that the surface of Mars is a sterilizing environment. There is UV there, there's a very oxidizing surface, so I'm not so much worried about the contamination of the surface. And it seems to me if you're going to look for extant life it is going to be at depth in the planet somewhere because it can't exist on the surface. But aside from that, let's assume that we do have a robotic program and we do have a series of sample returns, and let's further assume, for the moment, for the sake of argument, that each one is negative. You don't find life in each sample return. How many of those do you require before you declare that Mars does not have life and never has?
Image Credit: UGS
Michael Carr: Of course, we can't answer that question. We've got to sample different environments and we've got to ensure that we understand the planet well enough that we know the range of environments that are there. For example, you say it's unlikely that there is life near the surface today. We don't know whether active hydrothermal systems are present, in which you could have life almost at the surface. We don't know how deep below the surface one would have to go to find conditions where life terrestrial life could survive. Until we explore globally more of the planet, and go to some of these places where we're suspicious that terrestrial life could survive, I think we should defer sending people there.
Paul Spudis: You sort of set it up as a predicate, that in order to assure that we're not contaminating, we need to address this question first. And what I'm asking is, if you can't define the criteria by which you're willing to make that call, essentially you're saying, "Never go with people."
Michael Carr: I am not really saying that. But I'm saying that, given the range of environments on Mars, you should sample as many as could probably sustain life. Then, seeing what you find there, make some sort of prudent judgment that perhaps the chance of finding life right at the surface is pretty close to zero. You'll never prove that there's no life there.
Paul Spudis: So, essentially, it's a non-falsifiable hypothesis.
Image Credit: NASA
David Morrison: The problem is initially, as you say, on the surface. The surface is a pretty unpleasant place for terrestrial life. And so it may be possible to go there without risking a contamination of the subsurface. In that case, all you have to do is establish that there's no Mars life at the surface and you can defer till later the question of probing down perhaps kilometers below the surface to an aquifer. But it's a dynamic question. I don't think you can set requirements now for what we'll be doing 25 years from now.
Laurie Leshin: I have a specific question about the Moon, which we haven't talked about much here with you. In understanding the origin of life on our planet, the Moon has a very important role to play. I wonder if any of you have comments on how the science we can do on the Moon can help us in this quest to understand where we came from and where we're going, what role the Moon can play there, because that's where we're going first with humans.
David Morrison: The Moon is very exciting to geologists. But to biologists it's of interest also because it's the place we go to find out what the first billion years of history of Earth and Mars were like. And I know that my astrobiologists are interested in defining the conditions under which the planets formed, the early bombardment, the time scale for those events that were crucial at the time life was forming on Earth. So it's a very interesting place to study habitability, but perhaps not to study life itself.
Laurie Leshin: So in order to understand the snapshot in time when life was emerging on our planet - which is not well preserved on our planet, we don't have a good rock record of that - the Moon is a great way to go to explore that. Jonathan, do you want to say anything about that?
Jonathan Lunine: I was also going to say, and you articulated it already, that the first half billion years of the Earth's history is lost to us in the geologic record, and it's there on the Moon. So it's a crucially important object from that point of view. It could very easily have been that we would not have had the Moon. It was the result of a particular large impact at a particular angle and in a way we lucked out, I suppose. And that, too, is important because those large impacts that build terrestrial planets also brought in the water and the organics that were the raw material for life, and the leftover from that large impact is orbiting a quarter million miles away from us. So understanding its composition tells us something about the things that were hitting the Earth at the time and supplying these materials.
Image Credit: AMNH.org
Neil Tyson: Jonathan, you noted you had this dream of a perfect night sky even being a city person. Perhaps were you not a city person, you could not have dreamed it because it would be out there every night. So, in the city where there is no night sky, that's the place where you dream about a night sky - I'm wondering if that was part of it.
Jonathan Lunine: Well, it helped that I live four blocks from the Hayden Planetarium.
Neil Tyson: David, I think you made an assumption that if we find life on Mars, and we find that life to be DNA-based, then we would be related to Martians. Is there any way to test for whether life might have no trouble making DNA wherever life forms, so that DNA itself might be what's inevitable in wherever you would find life?
David Morrison: Well, that's a good question. We know all life is related on Earth. We can do the analysis of the genomes and see the amount of divergence between one microbe and another, which is related to the time since their last common ancestor. If we found a group of microbes on Mars that fit that pattern, but with a deep divergence billions of years ago so it's not just "Do DNA and RNA exist?" but are the patterns put together in ways that there is some resemblance to the common ancestry we have here? Then I think we would come to that conclusion. If it was totally different, we'd say this was an independent origin of life and there probably is a whole spectrum of interesting possibilities in between.
Neil Tyson: How much of the incentive to return samples from Mars or anywhere else is because people are not thinking more robotically about such an exercise? In this vision we are charged with thinking about how to use in situ resources, how to go far beyond what even we do today in terms of robotics, telerobotics, and the like. Why is it so hard to imagine setting up a remote lab so that you don't actually have to bring the rock back to Earth to put it in your Earth lab? Can you imagine a remote lab that does all the same things?
|Apollo 17 panorama, rover and giant boulder
David Morrison: The quick answer is no, not today. Whatever capability we have to build a lab on Mars, surely our labs back at Earth will be decades ahead of that. So by bringing it back you always have access to the best technology.
Michael Carr: There's a geologist at JSC (Johnson Space Center) who calculated the total mass of all the instruments that are currently working on the lunar samples. And it was a staggeringly large number. And it is not just the mass but the sophistication of the instruments and the sample preparation and so forth that are needed to prepare samples for analysis. I find it almost impossible to imagine a remote lab on the Moon or on Mars doing what we can do with samples returned here to the Earth.
Laurie Leshin: I'm not going to spend time arguing with Mike about whether or not we should send humans to Mars. What we're really talking about is intelligent sampling. You made the comment that if Opportunity hadn't had wheels and just was able to reach out, that really wouldn't have been very intelligent sampling. And so since it can drive over, it can be more intelligent. Well, humans would be the ultimate in intelligent sampling. At least we hope we would train them well and would have geologists in the bunch.
Michael Carr: I've just spent three months helping drive these rovers around Mars. I think we're doing fieldwork pretty well. We did intelligently look at that outcrop and sample it. We got microscopic imaging of it, we got analysis of it, we got mineralogy. We have a very limited set of instruments, and we were doing fieldwork right there at JPL (Jet Propulsion Laboratory).
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