NASA - National Aeronautics and Space Administration

Happy Martian Anniversary, Spirit and Opportunity!

I'm Jane Platt and you're listening to a podcast from NASA's Jet Propulsion Laboratory in Pasadena, California. The Mars Exploration Rovers have been on the red planet for one full Martian year! Does it seem longer than a year? Well, actually, it is. It will be two years in January 2006, but that's Earth years. Mars travels around the sun slower than Earth does, so a Mars year is longer. Joining us from New York today is Dr. Steve Squyres of Cornell University, principal investigator for the rovers' science instruments. In our last podcast, he talked about goals for this second Martian year for Opportunity ... finding bigger holes to climb into and bigger stacks of rocks to study. Steve, how will Opportunity find these bigger vistas?

Squyres: What we're doing right now is we're driving south, as fast as we can go, basically, trying to get into some terrain that is topographically higher and may offer a different kind of rocks. And then also out ahead of us, it's still more than a mile away, but out ahead of us is a spectacular crater, called Victoria crater. It's much deeper than Endurance Crater, and if we could get to that it could potentially provide access to even deeper layers. So we are basically off in search of new kinds of rock.

Q: And what about Spirit?

Squyres: Spirit's doing great. Spirit spent more than 400 Martian days climbing a mountain called Husband Hill. We got to the summit, took just a spectacular panorama from the summit, and we're now working our way down the far side and down into a kind of a mysterious region called the Inner Basin that we've sort of seen from a distance for a long time but not had a chance to sample yet. And we're very interested to see what we find there. The geology in the Columbia Hills where Spirit is, is far more complex than the stuff that we found at Meridiani, where Opportunity is. At Meridiani, you find these nice, flat, horizontal parallel layers, whereas in Gusev Carter in the Columbia Hills where Spirit now is, the geology is just all jumbled up. It's been busted up, moved around, there've been many, many, many impacts into this stuff that have really kind of thrashed things around quite a bit, and it makes it harder to read the geologic record here. But it makes for some intriguing puzzles to try to solve.

Q: Based on the findings of these two rovers that again have been up there almost two years, how would you sum up what you now know about Mars that you did not know two years ago. I know that's a really big question, but if you could just sort of synopsize, “We know Mars is this, we didn't know that before,” that kind of thing.

Squyres: Sure, I'll try. Mars is fundamentally a planet made of a kind of rock called basalt. It's a volcanic rock, and most of the rocks at the Martian surface are made of that stuff. Mars is a planet where the groundwater in many instances is sulfuric acid, and some very interesting things can happen when the sulfuric acid interacts with the basalt. When you have a little bit of interaction, you can take the rock and you can change its chemistry a little bit. You can make modifications to it that result in some of the very kind of faint water evidence I guess you could call it, that we see at a place like Gusev Crater, where Spirit is. But then when you have much greater amounts of water and they really flow through the rock and just completely alter its chemistry and then the water comes to the surface and evaporates away. You can make deposits of sulfates that are dramatically different from the rock from which they initially formed. And that's the kind of thing that we see over at Meridiani Planum where Opportunity is. Mars is the past was not—it's not what I was expecting. Ya' know a lot of us went there, expecting that, hoping that we'd find carbonates, that we'd find limestone basically that might preserve a record of a more dense atmosphere of carbon dioxide in the past. We haven't seen any limestone at all. What we found instead is sulfates, everywhere and evidence that the water was sulfuric acid. You can't make limestone when there's sulfuric acid around. What this is telling us is that the chemistry was very different from what we expected, or at least from what many of us expected, and that it was in many ways a rather chemically harsh place, but still a wet world, and probably a warmer world. And there's still a lot more to piece together here.

Q: And over the last couple of years, obviously landing day for Opportunity and for Spirit, those were major exciting events ...

Squyres: Oh, yeah…

Q: Unforgettable, actually. But in addition to those, were there, could you maybe pick one, two or three, if you had to, real wow moments when some data came back and you were just stunned by what you were seeing?

Squyres: That's a hard one. You know, when you learn things like this it doesn't usually come in one grand Eureka moment. You build up a body of evidence, and I think that's the real significance of this set of papers that we've just put out is that they're the first papers to really present that body of evidence in great detail. There certainly have been important milestones for us, milestones in our exploration. Ya' know, the first moment that we drove up to the lip of Endurance Crater and realized what an opportunity we had in front of us. The view from the summit of Husband Hill with Spirit when it finally got to the top and began to see down on the other side. I think most recently the fact that we've just completed a full Martian year. We've now had the chance to experience Mars in all of its seasons, and it really does change with the seasons. I mean, Mars in the winter and Mars in the summer are two very, very different places, and we've had a chance to experience all that. So there've been many milestones, but rather then one great “aha” moment, it was more a continuous and very satisfying buildup of evidence over time.

Q: And I guess, that's interesting that you say that there's not one Eureka moment, it's an ongoing process. I suppose as a scientist, you have to have a lot of patience, because you do get the data in dribs and drabs.

Squyres: Yeah, I mean this has been going on, as you say, for almost two years now. And you build up the evidence slowly, your understanding changes and improves with time, and it's a gradual learning process. It's, I think many expeditions of exploration and discovery have shared that. You sort of learn as you go.

Thank you, Steve, for joining us today. That was Dr. Steve Squyres of Cornell University, New York. And of course, we have a lot left to learn from the rovers as they continue their work. The have already far outlived their planned lifetime, so we are in extended bonus overtime now! More information on the Mars Rovers is online at www.nasa.gov/mars or http://marsrovers.jpl.nasa.gov . Other NASA podcasts are at www.nasa.gov/podcast . Thanks for joining us from NASA's Jet Propulsion Laboratory.