WET PLANET?
June 22, 2000

Data from NASA's Mars Global Survey suggests that water may have flown freely on Mars during "geologically-recent" times. Could water be under the surface? The principle investigator of the data discusses the implications of the findings.

Online NewsHour Special Reports: Space Exploration Mars Polar Lander One Giant Leap multimedia April 14, 2000: NASA accountability of failed missions and mismanagement Feb. 14, 2000: NASA scientists discuss launching the first spacecraft to orbit an asteroid. Dec. 7, 1999: Science experts discuss the future of space missions, after NASA's Mars Polar Lander failed to make contact with Earth. Dec. 2, 1999: The mission of the Mars Polar Lander Aug. 26, 1999: Chandra Observatory, has relayed spectacular images of exploding stars to NASA July 20, 1999: The 30th anniversary of Neil Armstrong's first steps on the moon. Dec. 8, 1998: An Online Q and A: The International Space Station Nov. 20, 1998: Russians send the first component of the International Space Station into orbit. March 6, 1998: NASA scientist Alan Binder discusses the new discovery of water on the moon. Feb. 27, 1998: Is the universe evolving more rapidly now than it has in the past? Dec. 31, 1997: The Hubble Telescope's clear images reach Earth. Oct. 15, 1997: NASA begins its seven year mission to explore Saturn. Oct. 2, 1997: Forty years after Sputnik first circled the Earth, historians examine its impact. Sept. 30, 1997: An interview with Mir astronauts. Browse the NewsHour's coverage of science     A NewsHour Extra report for students on whether there's life on Mars.   NASA Mars Exploration Program	TERENCE SMITH: Last December, NASA received bad news from Mars, when its polar Lander was lost on the planet surface. Today the news from the Mars Global Surveyor space craft was so exciting that one scientist said, "it blows my mind." Here to tell us about it is Michael Malin of Malin Space Science Systems in San Diego, and principle investigator analyzing photos from the surveyor.
	Evidence suggests free-flowing water
	TERENCE SMITH: Welcome, Mr. Malin. MICHAEL MALIN: Thank you. TERENCE SMITH: And congratulations. Tell us what you discovered from these pictures. MICHAEL MALIN: What we have found is apparent evidence for recent flowing of water across the surface of Mars. TERENCE SMITH: And by recent, you mean? MICHAEL MALIN: We don't know how recent. The thing is too young to be able to tell by the usual techniques that we use to date ages on planetary surfaces. TERENCE SMITH: So this would be important because in the past it was known that there was water on Mars many billions of years ago. MICHAEL MALIN: Correct. TERENCE SMITH: But now the suggestion is it might be more recent. MICHAEL MALIN: Right. We have known that there is ice on Mars, and we have known from photographic evidence that in ancient times, billions of years ago, there were catastrophic floods and river valleys. But we have not had the link between that ancient liquid water on the surface and today's ice, and we think that we've found that link in the pictures we've gotten in the last year. TERENCE SMITH: All right, we have some of those pictures. And let's take a look at them, and perhaps you can describe what we're seeing. MICHAEL MALIN: Sure. TERENCE SMITH: The first of these is, I gather, going to be on the cover of the journal Science. What does it show? MICHAEL MALIN: Well, I think your viewers can see what it shows. It's a gully. It's actually several gullies. These are big. The bar in the lower right corner shows a distance of about two city blocks. So these are about a mile long and a quarter of a mile wide. And the upper part, as you see in the upper part of this picture, is an area where the gully walls have collapsed. And the material from that collapse has spread out towards us down the channels, as you can see, at the far left and in the middle center of the image. TERENCE SMITH: Right. And it certainly looks like that on the bottom. Now the second shows a weeping pattern of these same gullies. MICHAEL MALIN: Right. TERENCE SMITH: Explain that. MICHAEL MALIN: This picture shows that these don't occur in isolation, that they often occur many in the same location. And you can see a layer of rock that's actually about 100 meters thick -- about the size of a football field, only vertically in relief -- from which we see these gullies emanating. And this is characteristic on the Earth, of water seeping out along the base of an impermeable or a layer through which water cannot percolate or move through. And it seeps out on the surface and flows down and carves these small gullies. TERENCE SMITH: It creates patterns like this. The third is the map of the seepage sites that you have. Explain that. MICHAEL MALIN: Yeah, the map shows probably the most puzzling aspect of finding these features. And that is, they're not where we would have expected, based on the atmospheric pressure and temperature on Mars. Mars is very cold, its atmospheric pressure is very low. And there are only a few places where liquid water could exist on the surface today, without explosively evaporating or boiling away. The darker zone in this map is where we would have expected to find features that were formed by liquid water. But, in fact, you'll see that all the small white dots occur in areas exclusive of that darker zone. So these features form pole-ward, or away from the pole, away from the equator, and they actually form on surfaces that also look away from the equator. So they're the coldest surfaces, rather than the warmest surfaces, and that's our biggest problem in explaining. TERENCE SMITH: So that's really surprising. MICHAEL MALIN: Yeah, it's very surprising. TERENCE SMITH: Now this next is a photo that includes actually three images that show the age, the respective age of the gullies. MICHAEL MALIN: This one shows in part the ages, and in part the different mechanisms that we considered. The picture on the left shows a canyon wall. The picture in the middle shows a crater wall. And the picture on the right shows one of our gullies. And you can see that the ones on the left and middle have these very faint streaks coming down. And that's a typical dry mass wasting, or mass land sliding process on Mars. Whereas, the one on the right is really different from it. And that's what caught our attention, that these are very different from other features on Mars.
	Water possibly moving below the surface
	TERENCE SMITH: This last image is a graphic depiction. And this is your chance to explain to us just what you think is happening here. MICHAEL MALIN: Okay. The... we have a hypothesis. This is a story that scientists sort of weave together from the various pieces of evidence. And we put this hypothesis together, and we publish it in scientific journals in the hope that the scientific community will evaluate it, critique it, find where we've made mistakes, perhaps find better evidence or alternative explanations. This model is the best guess we can come up with right now. And the idea is that there is a layer beneath the surface of Mars that is conducting water horizontally to escarpments, where the layer is cut by the wall of the escarpment and the water can leak out. But as I said earlier, the water's going to evaporate very rapidly. And in evaporating, it will cool the rock and actually cause any further water to freeze and form an ice barrier. But the water deep inside the rock is still moving laterally and still building up pressure behind this ice wall. What we think happens is that at some point, critical pressure is reached, the ice barrier is broken and the water behind that barrier comes flooding out in a very short-lived, almost flash flood-like event, that spreads rock, debris, and ice down the slope, undermines the upper slope, causes it to collapse, as well, and creates the gully and the channel that we saw in the earlier picture. TERENCE SMITH: Is there another possible explanation or explanations for this? Could it be lava, could it be something else other than water? MICHAEL MALIN: It's probably not lava, because we don't find any other associated volcanic features with these land forms. And they occur inside craters and in faulted areas where we don't think the volcanism can occur. We have searched very hard our minds and other analogies to find some other mechanism. One may be that there is trapped gas in the surface, that is periodically released and it fluidizes the material. I think the key is that we have evidence that some fluid, transported material cuts these channels. We're not quite sure what the fluid is. It could be gas fluidizing dirt, or it could be liquid water.
	Water would increase chances for Martian life
	TERENCE SMITH: If it's water, if it's liquid water, water in liquid form, what's the significance of that? MICHAEL MALIN: Well, there's the whole range of significance. To a geologist, it means that there is yet another material process that can shape the surface of Mars, one which we had never dreamed was active on Mars. And as a geologist and geo-morphologist who studies how things look on planets, that's very exciting. To the people who are studying the... or are participating in the search for life elsewhere in the universe, clearly the existence of liquid water on Mars is important because it's one of the necessary, if not sufficient elements in the equation for life. TERENCE SMITH: Right. Because...certainly on this planet, if you have water and energy, you generally have life. MICHAEL MALIN: That's right. And if those same rules would hold on Mars -- and there's no reason to expect or not that that would be the case for Mars -- but if it did hold, then the fact that we have now found one of the critical elements of that equation is an important thing.
	Martian water could help human exploration
	TERENCE SMITH: Does this have significance also for the prospects of exploration of Mars? MICHAEL MALIN: Yes. That was the next thing I wanted to say. Water is an extremely valuable resource. For human exploration, you can use it for water to drink, you can use it to extract oxygen for breathing. You can use extracted oxygen and hydrogen in fuel cells to transport power for electricity. And it also, hydrogen and oxygen is a propellant to bring you back to Earth. So it is one of the most valuable resources you could find on another planet. TERENCE SMITH: Now what you've found, of course, is evidence that there was water, or you think it's water -- liquefied form, not... You haven't found such water. MICHAEL MALIN: No, we have not found the water. What we have found is evidence that very strongly suggests that water in the near recent past has flowed across the surface. TERENCE SMITH: What happens next? What are the next steps now in following on from this information? MICHAEL MALIN: Well, there are three steps. We have Mars Global Surveyor, it is still at Mars, it is still taking pictures. It's an asset that we will use to try to test the hypothesis by looking for changes, and that might tell us how young or old these were by looking for the amalgam material that was transported, which would tell us perhaps whether it was water or this gas hypothesis. There are future missions, including the Mars Surveyor 2001, Mars 2003 missions, which may take experiments to Mars that would test part of the hypothesis. There's a European mission, the Mars Express, that has a radar sounder that may be able to detect the water. And of course, given the reshaping of the Mars exploration program that is presently going on at NASA, and among its advisors, I would expect that in the fall when that new program is formulated, that this will bear on some of the missions beyond 2003, that are coming down the pike. TERENCE SMITH: So this is the beginning of an exciting story, not the end of it. MICHAEL MALIN: Oh, absolutely. TERENCE SMITH: Okay. Michael Malin, thank you very much. MICHAEL MALIN: Thank you.