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For the rest of the hour, a Mars update. You know those two Mars rovers, they're still going. But the rover Spirit, already dragging a bum wheel, appears to be stuck in the sand a bit. And there's no truck around, no tow truck for 100 million miles or so.

The good news is that this week, researchers published a paper in the journal Science showing that the other rover, Opportunity, had a good road trip to the Victoria Crater, with parts of the crater showing signs of being shaped by water a long time ago.

Joining me now is Steve Squyres, the principal investigator at NASA's Mars Exploration Rover Mission, professor of astronomy at Cornell University.

Welcome back to SCIENCE FRIDAY.

Professor STEVE SQUYRES (Astronomy, Cornell University): Hey, Ira. How are you doing?

FLATOW: Hey. How are you doing?

Prof. SQUYRES: I'm doing great.

FLATOW: What - tell us what's happening with that stuck rover?

Prof. SQUYRES: Oh, man. This has been a tough one, Ira. The area of Mars that Spirit is exploring right now, we have learned, to our chagrin, is studded with invisible rover traps.

(Soundbite of laughter)

Prof. SQUYRES: It's horrible. It's horrible. They're lurking just beneath the surface in several places - we've come across a few of these now - are these deposits of what turns out to usually be ferric sulfate, iron sulfate, salts. And you can't see it because it's - on top of it, there's this thin kind of veneer of regular Martian soil. So you take a picture of it, it just looks like normal soil, and then you drive into it.

And it turns the salt deposits, they have very little cohesion. The grains don't stick together the way normal soil grains do. And you get into it, and the wheels just kind of spin and churn. And it's horrible stuff. We've gotten stuck in one of these once before, and we managed to power our way out of it.

The thing that makes it really tough for Spirit is that Spirit normally, you know, would have six wheels…

FLATOW: Right.

Prof. SQUYRES: …but the right front wheel is failed. And so, we're dragging this dead wheel. And so, for a five-wheel vehicle, when you get stuck in one of these traps, it's really hard. We've escape from these before.


Prof. SQUYRES: We're working hard at this one. But this is a tough spot.

FLATOW: You can't rock it back and forth like we do at the beach.

Prof. SQUYRES: No. There's a lot of things that you wish you could do that you can't. I liked your tow truck idea. But, no. Uh-uh.

(Soundbite of laughter)

FLATOW: Send, could you send the other rover over, give it a push?

Prof. SQUYRES: You know, it's completely on the other side of the planet, man. That would be a long drive.

(Soundbite of laughter)

Prof. SQUYRES: Even for Opportunity, that'd be asking a lot.

FLATOW: And how - is it up to its hubcaps? Is it pretty deep?

Prof. SQUYRES: Some of the wheels are sort of hubcap deep. Others, we think, are not. But it's a bad spot, you know? I mean, we've been in bad spots before. And if there's a way out of it…


Prof. SQUYRES: …we're going to find it.

FLATOW: So you're not…

Prof. SQUYRES: There is some good news. There is some good news.

FLATOW: You're not giving up on it. Oh, good news.

Prof. SQUYRES: Yeah. No, there is some good news. Yeah, let me tell you that, too. For several years now, Spirit has just been coated with dust. The solar rays had a huge amount of dust bottoms. Spirit's just been starving for power.

And at about the same time, we ran into this predicament, Mars also gave us a gift. And what happened was we experienced several wind gusts that have cleaned the rover off. The dust is gone. We've got an enormous amount of electrical power now, way more than we need. And what that means is it's bought us time. It gives us time - instead of having to try to rush before winter comes to solve this problem, we can actually sit down and go about it in a thoughtful methodical way, run some tests here on Earth, do all that we need to do. Mars has given us the time we need to try to solve this problem.

FLATOW: 1-800-989-8255. Now, I'm picturing, you know, my old Erector Set with my little rover that I made years ago.

Prof. SQUYRES: Yeah. Yeah.

FLATOW: You know, does that mean you're going - if you have extra battery power like that, you could spin the wheels faster or spin them longer…

Prof. SQUYRES: No, not really.

FLATOW: …or just before time is up (unintelligible) think about - get ready for winter?

Prof. SQUYRES: Yeah. What it does - see, as the seasons change, it becomes harder and harder to operate this vehicle, because the sun starts to sink low in the sky. And we were fearful, if we had a dirty rover, that we'd only have a short period of time to try to solve this problem before winter came upon us and we'd lose the vehicle.

FLATOW: Right.

Prof. SQUYRES: But with clean solar rays now, that buys us months. And that's a big, big advantage in a situation like this.

FLATOW: All right. Let's move to the other side of the planet, as you say.

Prof. SQUYRES: Yeah.

FLATOW: Let's talk about the mission of the other rover. How's that one doing?

Prof. SQUYRES: Opportunity is doing just great. We spent two years exploring this spectacular feature called - we call Victoria Crater. And now, we're headed to the south doing 50, 70, sometimes 100 meters a day, good, good long drives, heading for a distant, very difficult, very exciting target called Endeavour Crater. So Opportunity is trucking right along.

FLATOW: Mm-hmm. And what's the objective when you get there?

Prof. SQUYRES: Well, Endeavor Crater is fantastic. It's a long ways off. It's 13 kilometers away. And we've only done 16 kilometers, about 10 miles with Opportunity over its whole mission, so this is a long drive. But Endeavor is a huge crater. Its rim, we know by looking at it from orbit, is made of stuff completely different, from everything Opportunity has seen before and indeed from anything that Spirit had seen. So if we can get there - and it's probably going to take us a couple of years, if we're going to pull this off - but if we can get there, it's going to be like a whole new mission.

FLATOW: Oh, no kidding. You mean the rock is that different?

Prof. SQUYRES: It's completely different. It looks - from orbit, it looks - its spectral properties, its topography just looked dramatically different from anything we've ever seen.

FLATOW: Signs of water there?

Prof. SQUYRES: Yeah. Yup.

FLATOW: You published…

Prof. SQUYRES: And the minerals, so…

FLATOW: You published…

Prof. SQUYRES: So it's really exciting.

FLATOW: You published and reported it in Science about water.

Prof. SQUYRES: Yeah. That's right.

FLATOW: What was the essence of that report?

Prof. SQUYRES: Well, to understand the essence of the paper that we just published, you got to go back several years to our exploration of a crater we called Endurance Crater.

Endurance was the first big crater that Opportunity visited. And there, as we explored down into the crater, we got sort of a vertical slice through the rocks at that place, we found beneath the surface evidence that water had interacted with these rocks, had changed their texture, changed their chemistry, and so forth.

This is ground water. This isn't like the water you would swim in. It's like water you would draw from a well. But it was water beneath the surface, and it affected these rocks.

And what we didn't know, what we couldn't know, was - was this just a local phenomenon, was this - you know, this happened in this one place, but elsewhere it was different? Or was this something that was regional in scope? The plains that Opportunity is exploring cover and area the size of the state of Oklahoma. And you know, is the whole area like this? Or is this just a little local, you know, you know, outlier?

FLATOW: Right.

Prof. SQUYRES: So what we did was we then drove four miles, six kilometers to the south, to Victoria crater; it took us 21 months. It was a long, long arduous drive. And then when we got to Victoria, we spent two years there exploring along the rim, going down into the crater, doing the same kind of things that we had done in Endurance, although Victoria is a much bigger crater.

And what we found was that the same general sorts of patterns that we saw six kilometers to the north were repeated here. And what that's telling us is that this was not some little local anomaly. This in fact is something that probably affected this entire region.

FLATOW: And this new crater that you're headed for…

Prof. SQUYRES: Yeah.

FLATOW: …how does that compare?

Prof. SQUYRES: Well, the thing about Endeavor - this is - what makes Endeavor exciting is that it is actually not a crater that's formed in these sedimentary rocks that we've been exploring for five years. It actually is formed in the rock that is underneath the sediments. And then the rim of Endeavor is sticking up through those sediments like an island, a sea of sediments around it. And so it's a chance to actually see the older rocks that have - laying underneath where we've been driving for five and a half years now and know what lies beneath, which might be related to how these sediments formed in the first place. So it's a completely different rock type. It's nothing that we've been seen before.

FLATOW: Is it a straight shot there? Any obstacles?

Prof. SQUYRES: It pretty much is a straight shot. It's not an easy straight shot because there's lots of sand dunes and obstacles. It's kind of like negotiating a maze when you drive through this stuff. The good thing is we have pictures from orbit taken by the Mars Reconnaissance Orbiter spacecraft that is so high-resolution that it provides us with the map of the maze, and so we can find our way through it. And we use these pictures every day to negotiate our route.

FLATOW: But if you have those Martian rover sand traps in the way - in between…

Prof. SQUYRES: Fortunately, those don't seem to exist at the Opportunity site. Those only seem to exist at the Spirit site and really only in the part of the Spirit site that we're in right now.

FLATOW: 1-800-989-8255. A couple of questions. Let's go to Bill in Virginia Beach. Hi, Bill.

BILL (Caller): Hi. How you doing?

FLATOW: Fine. How are you?

BILL: Good. Thanks. I had a question. Is there a robot - is there an arm on the rover? Like a rover with arm?

Prof. SQUYRES: Oh, yeah. There definitely is. Yes, there is.

BILL: Have they tried like a bulldozer does and you, you know, make the shape of an A and you press the robot arm down in the sand and push the cab of the robot out of the sand trap? Or the salt trap?

Prof. SQUYRES: We have a long…

FLATOW: Like a pole vault.

(Soundbite of laughter)

Prof. SQUYRES: We have a long list - we have a long list of tricks that we might try. And that's one of the things on the list. Now, that arm was not designed for that job. And so if you're going to try to have things like that, you want to be very careful about how you do it. But that is indeed on our list of tricks to try if we need to.

FLATOW: Thanks, Bill. Good idea.

BILL: You're welcome. Thank you.

FLATOW: They're thinking out there. So you're not giving up on this?

Prof. SQUYRES: Oh, not at all. Not at all.

FLATOW: You'll just keep doing it until you get out of there?

Prof. SQUYRES: We'll keep doing it until we get out or it's clear that we can't get out. One of the two. But there are many, many things that we can try, and we're really just beginning to work our process there.

FLATOW: Well, as the winter comes, will the soil get any different in consistency that you could say, hey, let's wait, maybe it'll harden up, it will freeze a little more and not be able to get out then?

Prof. SQUYRES: We've thought about that one a little bit. I think probably a more, if you wanted to count on cold temperatures to change the properties of the soil, I think the thing to do would be to try to drive at night. It gets really cold at night on Mars and the soil properties may change a little bit at night. We've talked about that one too.

FLATOW: Are you able to do that?

Prof. SQUYRES: Yeah, because now we got the power to do it.

FLATOW: So - but you don't need a light on. Is there a headlight or something?

Prof. SQUYRES: No. But we could do - we could turn the wheels at fairly low temperatures. You'd have to heat the wheels up first and that would take a lot of power. But I think we could probably do some low-temperature maneuvering if that turned out to be the thing to try.

FLATOW: Here is a question from Second Life. What sort of batteries are on the Mars rovers?

Prof. SQUYRES: They're lithium ion batteries, just like you would have in your cell phone or your laptop. They're just really, really good ones.

FLATOW: And there is a new rover in store, right?

Prof. SQUYRES: That's right.

FLATOW: The bigger one.

Prof. SQUYRES: The Mars Science Laboratory.

FLATOW: How will be that different?

Prof. SQUYRES: It's different in a couple of really significant ways. It's much larger. Instead of using a solar power source, it has a nuclear power source. You've got a steady supply of electrical power, independent of dust accumulating on the vehicle. And it's also got some really cool scientific instruments, including an instrument that is going to be able to search for very, very trace abundances of organic molecules in the Martian rocks.

FLATOW: So it's going to have more of a laboratory on board.

Prof. SQUYRES: Yeah, it's got sort of a laboratory onboard, that's why it's called the Mars Science Laboratory.

FLATOW: There you go.

(Soundbite of laughter)

FLATOW: I cleared that up.

Prof. SQUYRES: Sorry.

FLATOW: We're talking with - no, it's my fault. We're talking with Steve Squyres this hour at SCIENCE FRIDAY from NPR News.

Talking about - when is that scheduled to launch?

Prof. SQUYRES: 2011.

FLATOW: 2011, it's almost around the corner.

Prof. SQUYRES: Yeah. Yup.

FLATOW: And now, that's not going to bounce to the surface. Is that going to go down by parachute?

Prof. SQUYRES: It uses parachute, just as we did. But then the final descent, as you say, does not use airbags like we did. Uses a technique called a sky crane, where - there are sort of two parts of the vehicle. There's an upper portion that has rocket motors that helps the vehicles descend together towards the surface, and then suspended below that, like it's hanging on a crane, is the rover. And when the rover touches down, you cut the cable and the other vehicle flies away and the rover's sitting there ready to go.

FLATOW: Can you explain to yourself why the rovers have lasted so much longer? They were made for a few months and now they're, what, almost five years, something like that?

Prof. SQUYRES: Yes. It's been a combination of three things, I think, Ira. One is that we build good hardware, and we're proud of that. You know, if you're going to accuse of over-engineering, I think we'll plead guilty as charged. We feel good about that. You know, the second reason is the wind gusts. We did not count on those, we did not expect them. And yet these wind gusts have continuously cleaned off both vehicles and given us a new lease on life.

The other thing is a trick that we've learned, and that is when it gets to be winter time, when the sun goes low in the northern sky, from where the Spirit rover is located, we can drive the rover onto a north-facing slope, tilt the solar rays towards the sun and get enough power to survive the winter. We've used that trick three winters in a row now. So it's been a combination of those three things.

FLATOW: Of course the Phoenix lander just sat there and died over the winter.

Prof. SQUYRES: Well, yeah. But to be fair, Phoenix was very close to the North Pole.

FLATOW: Right.

Prof. SQUYRES: The North Pole of Mars is a horrible place in the winter time. The sun goes away. It goes completely dark. Temperature drops to 120 degrees below zero. The vehicle becomes encased in a blanket of carbon dioxide snow. It's not place to be.

FLATOW: No. So you're closer to the equator, right?

Prof. SQUYRES: We're in a much more friendly part of Mars. Yes, sir.

FLATOW: And assuming you can get the rover out of the sand, where would it head to next? What would you have it do?

Prof. SQUYRES: Yeah. Spirit - we're hoping to head for, there's a very strange feature a couple hundred meters to the south of us that we've named Goddard(ph). It's a hole in the ground. It's a pit. But it's not circular. This thing is not an impact crater, it's something else. And you know, in this area where Spirit has been exploring, we've seen a lot of evidence for volcanic activity and for hydrothermal activity, for hot rocks interacting with water. And we think this pit may be a volcanic explosion crater, which is something nobody had ever seen on March before.

And so we're going to head for that and explore it and see what we can learn about both volcanic processes and water processes that have operated at this site.

FLATOW: How far away would that be?

Prof. SQUYRES: A couple hundred meters, pretty close. But you know…

FLATOW: I take…

Prof. SQUYRES: So close and yet so far. I mean, we've still got to get out of the sand first, right?

FLATOW: Well, let's say you get out of the sand. Are you now at a stage, since you've lasted so many years, willing to take a little bigger risk?

Prof. SQUYRES: Yeah. I think we sort are obligated to at this point. I mean, we're taking a big risk with Opportunity trying to go driving to this incredibly distant crater too.

You know, at some point you've done the easy stuff, okay, and you've discovered what you can by doing the things that you're doing and you've got a choice. You can either try to just do the safe stuff, do the easy stuff, preserve the vehicle, or you can try to push the envelope a little bit, try hard things and you know, take some risk in the process. They're named the Mars exploration rovers, okay? Exploration is part of the name. And we feel an obligation, you know, now that we've done the easy stuff and some of the kind of hard stuff to try doing the really hard stuff.

FLATOW: Is Google Earth on Mars? Can you see where the rovers have been?

Prof. SQUYRES: No. But there actually is a Google Mars. If you go to Google Earth and you invoke its Mars capability, you can actually see the terrain that we're operating in.

FLATOW: Well, good luck to you. Sounds exciting. And that's going to be a long trip to the other side of the…

Prof. SQUYRES: Yeah.

FLATOW: A couple of miles away, right, so…

Prof. SQUYRES: More than that.

FLATOW: More than that. How far exactly?

Prof. SQUYRES: To get to Endeavor Crater from where we are now is about 13 kilometers. So you know, getting - get to be seven or eight miles, yeah. It's a lot.

FLATOW: Wow. And at 100 yards at a time.

Prof. SQUYRES: Yeah.

FLATOW: Okay. Well, you've got a reason to come back again then.

Prof. SQUYRES: All right. Looking forward to it.

FLATOW: All right, Steve. Thank you very much for taking…

Prof. SQUYRES: Good to talk to you, Ira.

FLATOW: You too. Steve Squyres, who is lucky enough to be working as principal investigator of NASA's Mars Exploration Rover Mission, also professor of astronomy at that famous astronomical place, Cornell University.

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