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Recent Water Gushes and Craters on Mars
NARRATOR: Evidence of Mars gushers and craters sometime in the past five years.
I'm Jane Platt with a podcast from JPL - NASA's Jet Propulsion Laboratory in Pasadena, California.
Our guest today is Dr. Michael Malin of Malin Space Science Systems in San Diego. He's the principal investigator for the Mars Orbiter Camera on NASA's Mars Global Surveyor, and he's lead author of a most intriguing report in this week's journal science.
MIKE MALIN: Thank you.
NARRATOR: First of all, in 25 words or less, what is the news about water?
MALIN: The news about water is that we have found two gullies out of the 10,000 that we have observed that have fresh deposits that we believe were formed by water flowing out recently.
NARRATOR: How recently?
MALIN: Within the last five years.
NARRATOR: Within the last five years, so that's very recent?
MALIN: Very recent, what we have are before and after pictures of these two gullies that show a fresh, light deposit on the floor of the gully and out on the base of the gully.
NARRATOR: How do you know what you're seeing is evidence of water and not something else?
MALIN: There are basically several lines of evidence. The first is the.morphology of the features that we see suggests that they were emplaced by a afluidized material, as opposed to a liquid material, something that was dirt mixed in with something that gave it mobility. The attributes that we see, it moved very slowly on a steep slope, which means that it was changing its properties as it was moving downslope. But it's easily diverted around very, very subtle topography and it has very long, finger-like terminations at the ends of these flows. Those are all attributes of something that has liquid water in it.
NARRATOR: So you could tell by the shape and by the way it traveled?
MALIN: Yes by the way it traveled and the shape is what we see today, which gives us hints to how it traveled. The other thing is that the features we see are bright, they're not like white, but they're much brighter than the surrounding surfaces. Everything else that we've seen on Mars that is fresh or that has formed recently is dark. The reason it's normally dark is Mars is actually fairly bright, it's covered with light dust, and whenever you disturb that light dust, the surface gets darker, not lighter. So to see something that has moved across the surface of mars but is actually much lighter than the dust-covered surface, that's very, very unusual.
NARRATOR: How is it flowing, a constant stream, gushing?
MALIN: We think that the water is coming from deep in the ground. It's warmed as it gets closer to the center of Mars. The outer parts of Mars are really, really quite cold, but the inner part is probably still warm, just as the Earth's interior is warm.
As the water came up, it reached the surface and initially froze at the surface. But as more and more water came up, it would build pressure behind the frozen water in front of it and eventually it would break out of behind that barrier and flow down the surface. So we think there's an ice dam that is holding back water for some period of time, and then that dam breaks, and water comes out, and as it comes out, and as the dam breaks, it consists of rock debris from the rock around that water, it includes ice fragments from the dam and it includes liquid water. And it flows down these very steep slopes, 20, 30 degree slopes and picks up rock debris and spreads out and forms the deposit that we see. So what we think is that there's a trickle of water initially just sort of building up pressure behind the ice dam, and then eventually there's a rapid release of many thousands of cubic meters of water that comes out, like swimming pools amounts of waters come rushing out of the ground in a very short, brief event and then the surface refreezes, and then more water builds up time and pressure and then eventually breaks again.
NARRATOR: If somebody were standing in those gullies on Mars and were standing there for a long time because you said these gushes of water are periodic, could you describe what they would see when these gushes happen?
MALIN: Sure, but the first thing I'd say is don't stand in the gully, because it would be like being out in the desert during a flash flood.
NARRATOR: What does this mean in terms of the potential for life?
MALIN: I don't know, I'm not a biologist. Certainly I could tell you the general impression is that water is necessary in its liquid form for there to be life, certainly life as we know it. And if there is liquid water on Mars then theoretically it improves the possibility, the chances that there might be life on Mars. My personal view is I'm very skeptical that there's life on Mars because the environment is so extreme, and on the Earth in most extreme environments the normal forms of life on Earth that we find in extreme environments sort of evolved into those locations from a much broader population. It'd be very, very difficult to do on Mars.
NARRATOR: I'm sure you've had some lively discussions with your colleagues.
MALIN: You betcha. (chuckles)
NARRATOR: Part two of your discoveries that are appearing in this week's journal Science and that is also from Mars Global Surveyor and from your camera, the Mars Orbiter Camera, pertaining to craters on Mars. Tell me briefly about that.
MALIN: We serendipitously happened to observe a dark spot, very small, about a kilometer across in a wide-angle picture. Wide-angle pictures have a resolution at best about 230 240 meters per picture element. So this was a round spot that was only four or five pixels across. And one of my colleagues here, Ken Edgett, said, “Ya' know, that spot wasn't there before.” And he went and he proved to me that his knowledge was encyclopedic of Mars, and that in fact, the dark spot that we found hadn't been in earlier pictures. And we speculated what it could be. We thought it might be a windblown area or the shadow of Phobos. We excluded those and took a high-resolution image of it and found that it was a fresh crater, a crater that had formed between the time of those two pictures. And then we re-photographed about a little over 20 million square kilometers of Mars, which is about 30 percent of the planet, in the dustiest areas, and found 20 more craters that had formed in basically the last five or six years.
NARRATOR: What does it mean?
MALIN: First it allows us to determine how old surface features on Mars are. Craters accumulate with time, the more craters on a surface, the older that surface is. And we have basically up till now been using the models that I talked about to estimate how old various things are. Now we know from validating the models that those ages are in fact correct, and we can use those to decipher more of the geologic history of Mars.
NARRATOR: Well thank you so much for joining us to share your discoveries.
MALIN: You're welcome.
NARRATOR: We've been talking with Dr. Michael Malin of Malin Space Science Systems.
More info on Mars Global Surveryor, which JPL manages for NASA, is at www.nasa.gov/mars
Thanks for listening to this podcast from NASA's Jet Propulsion Laboratory.
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