Mars Rover Frees Itself From Sandy Dune
PASADENA, Calif. — The Mars rover Opportunity resumed rolling freely across the Martian surface Saturday after scientists freed it from a sand dune where it had been mired for nearly five weeks, NASA officials said.
Engineers at the Jet Propulsion Laboratory, which manages the mission, cheered when images beamed back to Earth showed the rover’s wheels were free.
"We’ve got a working rover on Mars that cost $400 million to build and … keep working," project manager Jim Erickson said. "I’d like to wear it out rather than lose it."
A photograph taken by Opportunity and posted on the laboratory’s Web site showed the long tracks of its wheels crossing a featureless dune.
Opportunity’s wheels started slipping April 26 during a planned 295-foot trip. While trying to drive over a foot-high sand dune, the robotic explorer stopped moving, its wheels hub-deep in soft soil.
Engineers spent weeks with an Opportunity mock-up figuring out what commands to give the robot to free it, but the maneuvers took time. The rover inched forward less than a foot in a month, losing most of its traction every time it tried to roll.
"It’s kind of like we were swimming through it," Erickson said.
But on Saturday morning, data showed that Opportunity was free at last and had moved several feet across the dune.
Erickson said engineers want to be sure the rover will not encounter any more patches that could trap it again. It will be Monday or Tuesday night before a test drive is ordered, he said.
Opportunity and its twin rover, Spirit, have been exploring opposite sides of Mars since landing in January 2004. Both rovers have long outlasted their primary, three-month missions.
First-Hand Account from Steve Squyres
Boy, this has been a good day.
We’ve had a feeling over the past several days that this was coming. On each of the last few drives, the rover slipped a little bit less than it had been for most of the extraction. In addition, the right bogey (the part of the suspension that the right middle and right wheels are mounted on) recently started moving in a way that suggested that the wheels were finally coming over the crest of the dune. And we knew from all our earth-based testing that when a stuck rover breaks free, it tends to do it very abruptly. So all the signs were suggesting that the big breakout was almost upon us. Still, it’s hard to describe how good it felt to check out the downlink this morning and see all six wheels back on solid ground again.
You develop pretty strong feelings for these vehicles once you’ve spent enough time with them, and when one of them gets into trouble you really sweat it until the trouble is over.
So what comes next? The first thing we’re going to do is simply take a very hard look at the stuff we were stuck in. Much of the worst terrain was under the belly of the rover through all of this, down where we couldn’t see it. From our new position, everything that was under us for all those weeks is now visible. So we’re going to take a little while just to look at where we were. We may also turn to take a look at our tracks (or trenches, or whatever you want to call them) with some of the instruments on the arm. But we’ll see about that one… we’ll only do it if we’re convinced it’s safe.
After that — and there is no timetable for any of this — we will begin a cautious set of moves to get us on our way again. And just so there’s no doubt about it, this little incident is not going to deter us from continuing our southward exploration. South is where we think the best science is, and we’re not going to turn tail and run because of one unfortunate episode.
Now if we find after continued driving that the southward road is simply impossible, then it’ll be time to start thinking about something else. But for now, south is where we plan to go.
And lest I forget our other baby in all the excitement… Spirit is doing very nicely. We were just about to hit the gas and head on out of here, but in the last couple of days something interesting and unexpected came up. Mini-TES, our infrared spectrometer, is a very nice compositional survey instrument. In other words, it’s a tool we can use quickly to look around and learn something about what rocks are made of.
We’ve been doing lots of Mini-TES observations on the rocks around Spirit for awhile now, it’s gotten to the point that nearly every rock type is pretty familiar. But late last week, we came across a rock called Backstay that looks, to Mini-TES, a bit different from anything we’ve ever seen before. It’s a loose rock, not bedrock, so it may be a piece of impact ejecta from someplace far away.
The Mini-TES spectrum is nothing wildly exotic… the thing certainly seems to be some kind of basalt. But if it’s a flavor of basalt we haven’t seen before, then it’s definitely worth a quick look. And luckily, a quick look is possible. Just about the time that we realized that Backstay was something interesting, our most recent drive had put us just four meters away from it. So the plan for the next few sols is to drive to Backstay and figure out what it is before moving on to anything new.
Time to go celebrate…
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On the Net:
Mars Exploration Rovers: http://marsrovers.jpl.nasa.gov/home/
Jet Propulsion Laboratory: http://www.jpl.nasa.gov/
