How To Avoid Contaminating Planetary Neighbors When the rovers Spirit and Opportunity hit Martian soil, scientists say they probably arrived with guests: thousands of bacteria. Planetary scientist Christopher McKay argues that future missions shouldn't dirty the planet in ways that subsequent generations can't clean up.

How To Avoid Contaminating Planetary Neighbors

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IRA FLATOW, host:

This is Science Friday from NPR News. I'm Ira Flatow. Later in the hour, a look at Google Earth's newest destinations: underwater and the Red Planet. But first, speaking of Mars, lots of science-fiction stories about the Martians invading the Earth - well, you know, a whole bunch of them - but you don't hear much about the Earth invading Mars. But in fact, we have been invading the Red Planet for decades, not we as humans, but thousands of bacteria that hitchhike aboard our space probes, like the Viking Lander 30 years ago, or the current rovers, Spirit and Opportunity, or the Phoenix Lander. Now, scientists have thought about this potential contamination of other planets, and over 40 years ago, the U.S. signed something called the Outer Space Treaty, which requires the U.S. and other space-faring nations that signed it to avoid, quote, "harmful contamination of other corners of the solar system."

But my next guest says that that policy is not quite what we need today. He says we need something a little bit stronger. We're going to talk about that up first, and if you'd like to discuss it, our number is 1-800-989-8255, 1-800-989-TALK. You can Twitter. Our Tweet number is - our Twitter is @SciFri, the @ sign, SciFri. Also, we're podcasting and blogging at Science Friday. Let me introduce my guest. Christopher McKay is a planetary scientist in the Space Science Division of NASA Ames Research Center in Moffett Field, California. He joins us by phone today. Welcome to Science Friday.

Dr. CHRISTOPHER P. MCKAY (Planetary Scientist, NASA Ames Research Center): Happy to be on.

FLATOW: How did these bacteria get aboard these robots we send to Mars?

Dr. MCKAY: Well, the robots that we send to Mars are assembled under very clean conditions, under clean rooms. Everyone is wearing white bunny suits and so on. So, they are very clean, but they are not sterilized. So, we know that the spacecrafts that we've been sending after Viking carry a certain amount of bacteria.

FLATOW: Mm-hmm. So, Viking doesn't carry bacteria?

Dr. MCKAY: Well, Viking, there was an attempt to sterilize it because, one, we didn't know much about Mars then, and two, it had light detection experiments on it. So, Viking, there was an attempt to sterilize it, although looking backwards at what they did for Viking, we realize that it probably was not a rigorous sterilization.

FLATOW: Not something you'd do in an operating theater.

Dr. MCKAY: Yeah, not something they do with medical instruments, that's for sure, not that level of cleanliness.

FLATOW: Well, would it be possible, then, that over the years, over the 30 years that Viking has been there and other probes that followed, that the bacteria might have survived on the surface of Mars?

Dr. MCKAY: Well, they would survive, the ones that are not exposed directly to the ultraviolet radiation. Mars' atmosphere does not have oxygen or ozone, and so, there's an intense biocidal radiation from the sun that reaches all the way to the surface that would kill any organism unfortunate enough to be exposed to the sunlight within minutes. But organisms inside the spacecraft, shielded by metal, would not experience that radiation. They would not be able to grow; conditions are too dry and cold. But they would not be dead either; they'd be dormant. And they would stay dormant and viable, recoverable, for many hundreds of thousands of years. Eventually, they'd be killed by cosmic radiation.

FLATOW: So, if we had a shovel or a corkscrew or a driller on one of these landers that was going to penetrate way down below the surface, it might inject bacteria down there.

Dr. MCKAY: Well, if we did something that was deep below the surface, then we would no longer have the protection of this biocidal ultraviolet light that's killing and sterilizing everything on the surface. Then, anything we release could grow. And if we were drilling down, say, to reach an aquifer below the surface and we didn't have sterilized tools, then we would make a serious contamination, which is something we haven't done yet. So far, all the contamination that we've put on Mars is reversible. We could go and, in a sense, clean up the litter, bring the pieces back, and we would have removed the contamination because the contamination doesn't grow on the surface.

FLATOW: Mm-hmm. But in the future, are we planning on missions where we might be able to be in that danger?

Dr. MCKAY: Well, I hope so. I'm hoping to advocate for missions that drill down deep below the surface of Mars. That's, to me, the interesting frontier. But once we go below the surface, we're no longer operating in this nice environment of dangerous ultraviolet light, which is, in a sense, keeping things clean for us. Now, we have to be much more careful and think much more carefully about what we're doing where. And the point is, is that what we do on the surface may be different from what we need to do when we start exploring below the surface.

FLATOW: Well, this agreement that we signed 40 years ago, the U.S. signed 40 years ago, the Outer Space Treaty, does it not require us to be that careful?

Dr. MCKAY: Well, the Outer Space Treaty and the Planetary Protection Policies that come from it have, as their basis, protecting Mars for scientific investigation. So, it's the idea of being clean so that other scientists don't get bad results, and that's a policy or a principle that's done us well, but there's two - I think there's two issues with that policy. One is this notion of drilling deep underground and possibly contaminating something that's irreversible that, we can never undo, and second, it's not clear how that policy extends to human exploration, when humans are on Mars and they're doing things that have nothing to do with science. If, for example, a human mission is drilling a well to get water for - as a drinking source, that's not really a scientific exploration. Does that mean it's not subject to these rules? So, I think it's time to relook at this fundamental principle, move away from preserving science to something that deals more with understanding the potential for biological contamination, something I call making the exploration biologically reversible. So, in short, it says, don't do anything that you can't undo if down the road you realize you might want to undo it.

FLATOW: So, what do you think is necessary? A new conference? A new agreement?

Dr. MCKAY: Well, yeah, I think COSPAR, which is the international organization that implements these policies, should have a conference - and they're planning to - to reexamine this and to change the basis of planetary protection from scientific controls and scientific cleanliness to biologically reversible. And so, we should decide that all future exploration on Mars, including human exploration, should be conducted in such a way that it is biologically reversible.

FLATOW: And what about the other direction? Could there be life forms deep below that we bring back with us?

Dr. MCKAY: Well, that's a whole different issue, of course, which is that of returning samples to Earth. And I'm not addressing that at all in this current work, but that's an important issue and deals with agencies outside of NASA that are responsible for bringing biological materials back into the U.S. and so on. And that's - there, the constraints are very strict. The current approach, as I understand it, is that samples brought back from Mars, even from the surface which is experiencing this UV, would be treated as if they were very dangerous and contained in facilities like those facilities that are used to investigate very dangerous diseases like Ebola and small pox and whatnot.

FLATOW: Mm-hmm. In your commentary, you mention the possibility of someday warming Mars to help alien life to flourish. What's that? What's the idea there?

Dr. MCKAY: Well, this one of the things that motivates me to advocate for biologically reversible exploration. Suppose we go to Mars and we do find that there's life there, and that that life is dormant, maybe frozen in the polar caps, but more importantly, we find that that life represents a complete different type of life, a second genesis of life. Well, I would argue that what we ought to do then is figure out how we can warm up Mars to make it a better place for that life to grow. In other words, help the Martian life that's now frozen and dormant re-colonize its own planet. If we did that, though, and we had left our contamination there, that water would sweep across our old spacecraft, break them open, and the bugs inside would now be able to grow, and they would be competing for - with the Martian life. So, there really would be, as you said, a war of the worlds, with the invaders from Earth now coming - springing out of their spacecraft and coming to life. So, before we did that, we'd have to go and retrieve all those spacecrafts. We'd have to reverse the contamination that we've done, which is possible if we make sure that the contamination stays reversible.

FLATOW: Mm-hmm. So, you would go out and clean up all the litter of the old non-working spacecraft we have around the planet?

Dr. MCKAY: Exactly.

FLATOW: And how would you do that?

Dr. MCKAY: Well, we know where they are. We've got pictures from orbit where we can see all these spacecraft. It would be expensive, for sure. But if we are motivated by having discovered a second genesis, you would think that the level of interest would be quite high.

FLATOW: Now, I guess if we are ever at that point that we are able - have the technology to discover that second genesis, this would be a minor point.

Dr. MCKAY: Exactly, exactly. All of a sudden, the notion of going and cleaning up a little litter in order to be able to recreate a biosphere...

(Soundbite of laughter)

Dr. MCKAY: That's not so bad.

FLATOW: We've discovered life on Mars, and oh, by the way, there's some junk still left.

Dr. MCKAY: Yeah, but we need to clean it up before we do anything.

(Soundbite of laughter)

FLATOW: How far along is your proposal to come up with this new idea and to implement it?

Dr. MCKAY: Well, it's just an idea at this point.

FLATOW: Yeah.

Dr. MCKAY: And so, what needs to be done is first, COSPAR needs to have this committee, and these collected experts need to discuss it. And if it does get seriously considered, then researchers will have to think through what are the implications of it. If we do, do this, what will we have to do different? Well, for example, if we start doing drills, then those drills have to be rigorously sterilized before they go underground. Well, how do we do that?

FLATOW: Right.

Dr. MCKAY: We would have to look at these sorts of technologies in different approaches.

FLATOW: Well, we also - well, let's say, if we have astronauts, could they not be carrying their own bacteria on their spacesuits and things and transferring it to the ground?

Dr. MCKAY: For sure, they will. And as long as the astronauts are on the surface, then they are fine. If astronauts - like, for example, when the astronauts were on the Moon, their spacesuits were venting water out the back of their spaceships - spacesuits into the environment. Well, on the Moon and on Mars, any bacteria that's in that water being vented into the atmosphere are just being killed very rapidly by the ultraviolet light. It's only when the astronauts start doing something like drilling a deep aquifer that takes their activities outside the surface domain that we have a problem. So, even human - a human base on the surface would be biologically reversible. The contamination that's there could be reversed if we wanted to in some future time.

FLATOW: As far as we know, it could be reversed.

Dr. MCKAY: Right, as far as we know.

FLATOW: I mean, there might be - I keep thinking of "Jurassic Park," where, you know, things happen that are unexpected.

Dr. MCKAY: Exactly. So, we always have to be vigilant...

FLATOW: Life will win out, as it said, yeah. And as far as the Moon, you're not concerned about contamination of the Moon?

Dr. MCKAY: No, we've definitely contaminated the Moon. We're not worried about the fact that we've contaminated the Moon because we don't think that it ever had life, no chance of an indigenous second genesis there, and we don't think there's much prospects for it to sustain a global biosphere in the future. So, the Moon is a dead, Jim.

(Soundbite of laughter)

FLATOW: All right. That's - some interesting conclusion words we've had on this program, but never that one. Thank you very much, Dr. McKay, for taking your time to be with us.

Dr. MCKAY: You bet.

FLATOW: We'll be following you. Christopher McKay is a planetary scientist in the Space Science Division of NASA Ames Research Center in Moffett Field, California. We're going to change gears, and I guess he was talking to Jim on "Star Trek." Who's dead, Jim? I guess so. Captain Kirk is not going to be with us, but we're going to move on and talk a lot more about how you can explore Mars on your own if you'd like. So, stay with us. We'll be right back.

(Soundbite of music)

FLATOW: I'm Ira Flatow. This is Science Friday from NPR News.

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