More Evidence Of A Wet Past On Mars

Using data collected by the Mars Reconnaissance Orbiter, researchers say they’ve found evidence that more of Mars than previously thought was once covered by water. Science News astronomy writer Ron Cowen describes the research and other recent news about Mars and its watery past.

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IRA FLATOW, host:

This is SCIENCE FRIDAY from NPR. I'm Ira Flatow. Evidence is mounting that Mars was a very, very wet planet billions of years ago. But how wet was it, oceans worth, lakes, rivers? And if it was wet, where did all that water go?

Those questions are getting more attention recently with the publication of new research analyzing the Red Planet's watery history. Joining me now to sort it out for us is Ron Cowen. He is an astronomy writer for Science News. You can find his articles on water and Mars at sciencenews.org. Welcome back, Ron.

Mr. RON COWEN (Astronomy Writer, Science News): Thanks, Ira, hi.

FLATOW: Lots of evidence for water. What's going on about the oceans here?

Mr. COWEN: There may be oceans, or there may be just shallow, localized patches of water. It's unclear. I mean, some of the people go back and forth, even in the new research. Some of the new work is saying that in the northern plains, which is really flat, people have looked at dried-up - what appear to be dried-up river deltas.

And they all seem to be at the same altitude, which is what you'd expect if there was an ocean there that kind of flattened everything. And these people in the June 13th Nature Geoscience say that there could be there could have been an ocean that formed this region like this, and it would've been I'm sorry I'm going to use meters - but it's a 550-meter-deep ocean if we spread across the entire planet.

But there's other people, however, who say that, you know, from the chemical evidence, if there was water, you ought to see a lot of minerals that were altered by water, clays, like the clays we have at the bottom of the ocean.

And there are some in the north and even more so, apparently, in the south of Mars, but not a lot. And then there so there are people who say, well, you know, there never was an ocean. Maybe there were brief wet periods, maybe up to say 10,000 years, and then it stopped.

And that may have been good for localized habitats for life, but it was not an ocean, and it may not have been global. So there's people sort of going back and forth or debating on both sides of the issue, really.

FLATOW: One other piece of evidence that they've published was the finding of some, what they think may be 40,000 dry riverbeds. That would carry a lot of water, would it...

Mr. COWEN: Right, and that would have been that's where they get the idea of a 550-meter-deep ocean. That's right. But then I know that there are other people like Phil Christensen, who's a scientist who's on many of the Mars missions, saying that, you know, such things like these dried-up riverbeds, well, you might have only needed water for, say, 10,000 years at most to form these, and then somehow it went away. And he just keeps saying that the mineral evidence, the clays and minerals are just they are there on Mars but not in large amounts.

And there's a mineral called olivine, which is very, very susceptible to being altered by water and changed into other compounds, but there is a lot of olivine on Mars, and that would indicate, well, maybe there wasn't water because there shouldn't be so much olivine there if there was an ocean.

So people agree that 3.5 billion years ago or so, there was some water, but it's not clear how much. What people are telling me, too, is that the Mars Science Laboratory, which is supposed to be launched in late 2011 and land on Mars in 2012, that they should pick a place where there is a little bit of this chemical evidence and, you know, look around there, dig around there, and maybe that may really help settle the question. Or go some of these places, again, where there was localized water, and look for life there.

FLATOW: So they're saying the only way you're going to really settle it is to send something there.

Mr. COWEN: That's right.

FLATOW: To dig a hole.

Mr. COWEN: To one of these interesting places where they have found these what they call phyllosilicates, which are really clays that have been formed in the presence of water. Go and take a look there because there's some new research where people have a lot of these places where there is chemical evidence for water, the reason they know that is that impactors have pummeled Mars and excavated through the lava that covers a lot of Mars, excavated deep down and found these chemical signatures of water-altered minerals.

And so people are saying, well, go and land there because that might be one of the most interesting places for life and to tell exactly how much water was there and when.

FLATOW: And of course, the question is if there was this much water there, where did it all go?

Mr. COWEN: Right, that's true, too. Now, some of it may have evaporated. Some of it may be now beneath the surface, maybe just beneath the surface, and some of it may have migrated or frozen at the poles. All of that is maybe true and, you know, people have suggested drilling into Mars, and some of these frozen deposits of water may not be that far beneath the surface. But that is also still a puzzle, yes.

FLATOW: Is there anything that looks like a shoreline that would be leftover...

Mr. COWEN: Yes. In, well, some people say in the northern parts of Mars, in the northern plains, there are what looks like shorelines. And other people are debating that and saying, well, maybe, and then saying okay, these may look like shorelines, but then why don't we see all these water-altered clays that should accompany that?

FLATOW: But wouldn't you if you just think it through a little bit about how the Earth got to be wet, right, and the theory now is that there were comets carrying water, things like that, to our surface, well, Mars is almost the same size as Earth. Wouldn't we think it would be bombarded with the same kind of comets creating oceans and water like that?

Mr. COWEN: Right, or right, or those, there was an early period when Earth and Mars and a lot of the inner solar system was bombarded by asteroids and comets. And what some people say is yes, that may have been when water was delivered, but it may have been just to localized places on Mars. And yes, Earth has these oceans, it may be that Mars never had oceans, that it was just small areas where maybe it melted the ice where these impactors came, and there was a wonderful habitat for a short time. And maybe it was, though short, long enough for life to have gotten a foothold, but then it got cold again after this period of intense bombardment, which we think happened about 3.9 ago billion ended.

So year, but yes, there could have been water delivered in the same way as Earth.

FLATOW: It just seems to be, you know, it seems to be illogical, but of course, science is not logical in many aspects.

Mr. COWEN: Right. No, no, it's just that people are I think there's this tension, as I said, between all these wonderful-looking, intriguing, dried-up riverbeds and deltas and things that look like much bigger than our Grand Canyon - that presumably were carved by water on Mars, and yet we don't see the chemical compounds pervasively that we think should be there.

Now, some people say that, you know, Mars was so much blanketed over by lava that we don't have a whole lot of windows deep down to where these water-altered minerals may be hiding, and maybe that's the answer. Maybe it is more widespread, and we just don't see it because we don't have that many places where more recently, asteroids gouged into the surface and exposed these regions.

But again, that's why they're saying, you know...

FLATOW: You've got to go there and...

Mr. COWEN: You've got to go there, and you've got pick a really great place for the lander.

FLATOW: The Mars Rovers that are there are not made to do that?

Mr. COWEN: That's right. They're not I mean, they are they're just more very much on the surface, and they don't, they can just sort of scratch the surface a bit.

They do go to places where there have been excavations, and they have found definitely some evidence of water sulfates, which are water-altered minerals. But we'd now like to go to a place where these phyllosilicates, as they call them, have really been exposed by big impact craters.

FLATOW: Would they be easily landable places, or would we be taking a chance?

Mr. COWEN: That might be somewhat of a challenge, but I think that there - but some of these places I think are on NASA's target list, or there are planetary scientists telling NASA that these would be interesting places to take a look, and it would be worth it to consider it as candidates, candidate landing sites, yes.

FLATOW: And we still have orbiters looking down?

Mr. COWEN: Sure, yeah.

FLATOW: The Europeans have had their missions we've heard about.

Mr. COWEN: Mars Express, and in fact, some of the recent evidence for, in fact, finding some chemical compounds like clays in the north for the first time were found by Mars Express, and I think the Mars NASA's Mars Reconnaissance Orbiter both.

And that was actually a paper in the June 25th Science, saying that no, you didn't need an ocean to do this, but shallow amounts of water were both in the south and the north.

So some of this all sounds a bit contradictory I realize, or a little confusing, but this story still is being played out, really, and what's exciting is, I mean, they're not just arguing. They're arguing with data, and more data is to come.

FLATOW: And we have to argue only from what we know about what we see here on Earth.

Mr. COWEN: That's true, and the point is there are places on Earth where we call them hydrothermal vents where there, you know, there is water, and actually high-temperature places in the sea that wouldn't seem to be hospitable for life but in fact are. And people are saying if there was an impact that struck Mars and melted some water for a short amount of time, hey, that might have been good enough for some sort of life to have begun.

FLATOW: Yeah. All right, Ron, fascinating.

Mr. COWEN: Okay.

FLATOW: Thanks for joining us.

Mr. COWEN: Thank you.

FLATOW: Thanks for taking off from your vacation.

Mr. COWEN: Thanks.

FLATOW: I know you're on vacation.

Mr. COWEN: I appreciate you saying that. Okay.

FLATOW: You're welcome. Bye-bye. Ron Cowen is astronomy writer for Science News. You can catch his articles at sciencenews.org. And we always thank folks who take off from vacation to be with us.

We're going to take a break, and we're not on vacation. We're talking we're going to switch gears and talk about a new kind of life. Remember Craig Venter and his Synthia? Well, the president has a panel that he'd like to have them discuss what to do about this new form of life. So stick with us. We'll be right back and talk about synthetic biology. Don't go away.

(Soundbite of music)

FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

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