Image: Rover tracks
NASA / JPL
A view from one of the Opportunity rover's hazard avoidance cameras looks back at the deep ruts in the fine Martian soil left by the rover's wheels.
By Alan Boyle Science editor
msnbc.com
updated 6/4/2005 8:39:59 PM ET 2005-06-05T00:39:59

NASA's Opportunity rover has broken free from the Martian sand dune where it had been stuck for more than a month, the mission's top scientist announced Saturday.

"We're out of the trench, and we're back on the surface again," Cornell astronomer Steve Squyres, principal investigator for the Mars Exploration Rovers, told MSNBC.com.

In a mission update, Squyres reported that data from the previous day's activities at Meridiani Planum showed all six of the rover's wheels on top of the soil.

"We've been confident all along that this would happen, but still ... what a relief!" he wrote.

The Opportunity rover and Spirit, its twin on the other side of Mars, have been studying the Red Planet from the surface since January 2004. Last year Opportunity sent back headline-grabbing evidence that its landing site was drenched with water in ancient times, and in recent weeks Spirit has been sending back findings that point to a violent geological past as well as the presence of water in ancient times.

Careful extraction
In late April, during a southward trek toward a crater called Erebus, Opportunity's wheels became mired in the crest of a foot-high (30-centimeter-high) sand dune. Mission managers took weeks to plot out a strategy for getting out of the dune, going so far as to try out scenarios with a test model of the rover in a simulated Martian sandbox at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The rover team commanded the machine to reposition its wheels, then go through a series of spins that pushed the rover forward an inch at a time. Opportunity broke free after making about 3 feet (93 centimeters) of inch-by-inch progress — a sudden breakthrough that was in line with what happened in the Pasadena sandbox.

Squyres told MSNBC.com that the rover's next task would be to survey the surrounding terrain, particularly the dune crest where it got hung up.

"We're going to study the hell out of the dune that got us. ... It's going to be a couple of days before we try any moves at all," he said.

Where will Opportunity go?
Eventually, Opportunity will resume its southward trek, heading first for a bright feature nicknamed the Erebus Highway, about 130 yards (120 meters) away, Squyres said. The "highway" could be a stretch of exposed bedrock, leading toward Erebus Crater — which would be a very good thing for Squyres and his colleagues. Or it could be a huge pile of Martian dust.

"If it's dust, then we've got to stop and rethink a whole bunch of things," Squyres said.

Squyres said the mission team intended to have Opportunity press on to Erebus Crater, roughly 440 yards (400 meters) away, despite the past month's difficulties. "To just turn tail and run after we've had one unfortunate event is just not the way we're going to do business," he said.

But he said Opportunity would go at a slower pace from here on out, taking more advantage of the safety measures built into its software.

"The first rule in a situation like this is, do no harm," Squyres said. "These are literally priceless machines. ... We're going to move thoughtfully on this from now on."

NBC News space analyst James Oberg contributed to this report.

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