Designed to operate for at least 90 days on the surface of Mars, project engineers had high hopes that one or both of the Mars Exploration Rovers -- Spirit and Opportunity -- would manage to survive a bit longer than that as they creeped across the red planet looking for signs of a watery past.
But no one in their wildest dreams ever imagined just how long the compact solar-powered robots would actually last.
Opportunity landed on the red planet nine years ago Friday, just after midnight EST on Jan. 25, 2004, three weeks after Spirit bounced to an airbag-cushioned landing on the other side of the planet.
For both rovers, three months came and went. Then they made it a full year, then two. And so it went, year after year, to everyone's ongoing amazement.
Spirit finally went off the air in March 2010, stuck in sandy soil and unable to favorably orient itself toward the low sun during the harsh martian winter. But Opportunity remains in good health as it moves into its tenth year of operations, exploring the rim of Endeavour Crater, a 14-mile-wide impact basin in a region known as Meridiani Planum.
Principal investigator Steve Squyres of Cornell University discussed the rover's current health and plans for the future in an interview earlier this week with CBS News' William Harwood.
Q: How's Opportunity hanging in there?
A: The prospects for future operations appear good, but we voided the warranty on this thing so many years ago that we just sort of treat every day as a gift at this point. We have no idea how much longer this vehicle's going to last. It could last for years, it could die tomorrow. We're just pushing it as hard as we can right now and trying to squeeze everything out of it we can. So no guarantees. But right now, the vehicle's in great shape. The vehicle's healthy, we're doing good science and lots of good stuff is happening.
Q: Where is Opportunity right now and what's it been doing lately?
A: After lots and lots of driving, we've gotten to this place we call Matijevic Hill. We have found the place where, from orbit, we can see clay minerals. So we are in clay-bearing strata and what we are seeing is a geology and geochemistry that's different from anything we've seen before with either rover. There are all sorts of interesting, puzzling problems to solve here. We're working out way through them.
The most recent ... is we found some time ago these little, tiny veins, these very light kind of veins in the rock here and what we've learned in just the last week is they're made of calcium sulfate. Now, I'm not ready to say what form of calcium sulfate that is we've found. We found big, fat calcium sulfate veins over at a place alled Homestake earlier and those, it turned out, were probably gypsum. These we're still working on, whether or not they're gypsum. But they are certrainly calcium sulfate.
We're currently wrapping up our investigation of these veins and then we're about to go and try to figure out the composition of these little round things we're calling 'newberries.' They look like blueberries [iron-rich spherical nodules observed by Opportunity shortly after landing], but they're not.
Q: What is the significance of the veins you've seen?
A: The significance of these veins is that they were precipitated from water. I mean, you had water flowing through fractures that had calcium sulfate dissolved in it and the calcium sulfate precipitated out in the veins. It's really, really compelling evidence for water flowing through fractures.
Q: So there's no question Mars had flowing water in its past. The question now, I guess, is how long the water persisted?
A: The idea, was there ever liquid water on Mars, that's been resolved. It's been resolved by Spirit, it's been resolved by Opportunity, it's been resolved by Curiosity, it's been amply resolved from orbit as well. So now we're delving into the details. How long was it there? What was the chemistry of this stuff, what was dissolved in it, what was the pH? With these rovers we're starting to delve much more deeply into what it means as opposed to just was it there.
Q: Opportunity has now covered a bit more than 22 miles since landing. Where are you off to next?
A: South. We're going to finish up our work at Matijevic Hill as quickly as we can. That's going to take several more weeks to do because we still have a lot of stuff on our to-do list. But after that, we're going to head south. The rim of Endeavour Crater sort of sticks up through the sulfate sandstones we spent so many years driving around on and there's a number of these rim segments we can explore.
The next one we're going to head to is south of our current location, so we will be heading across a gap in the rim, a place we call Botony Bay, and then up onto the next rim segment to the south. There are two hills to the south of us, one called Solander Point and farther south than that a great big thing called Cape Tribulation.
Q: Is there a long-range goal beyond that?
A: Well, Cape Tribulation is at least as big as Husband Hill [explored by Spirit earlier in its mission], so we've got some major mountaineering ahead of us with this rover. Endeavour Crater is so large, there's the interior of it there's a big, big, big long stretch of rim that we can explore, there's enough here to keep us busy for years.
Q: You know, I can remember being in the clean room at the Kennedy Space Center before launch and not even imagining that one of the rovers could possibly survive this long in such a tough environment.
A: There are two things, I think, that really make this stand out as being remarkable. One is that as you say, it's been a very challenging environment. Not just the fact that there's dirt and dust everywhere, but remember, between daytime and night on Mars, the temperature changes by a hundred degrees Celsius. So we've been through 3,000-plus thermal cycles, hot-cold, hot-cold, hot-cold. That's very tough on a spacecraft.
The other thing that's remarkable is that in contrast to most of the spacecraft we deal with, this thing has a hell of a lot of moving parts. There are so many motors and gearboxes on this thing, and they're still working! Those two things are what really make this remarkable to me.
Q: Given your experience with Spirit and Opportunity, I assume you have some optimism that NASA's newest rover, Curiosity, might last longer than its two-year design life.
A: I do. I have lots of optimism for Curiosity. It was designed from the outset to last much longer than Spirit and Opportunity were. It's Mars, bad stuff can happen, right? But I am optimistic that Curiosity will have a long and fruitful mission.