Image: Opportunity view
NASA's Opportunity rover takes a wide-angle look at its surroundings amid the drifts of Meridiani Planum after rolling out of a sand trap.
By Alan Boyle Science editor
updated 6/6/2005 4:14:09 PM ET 2005-06-06T20:14:09

Like any car driver who has weathered a close call, the engineers steering NASA's Opportunity rover on the Martian surface are already sticking to safer driving techniques now that the six-wheeled robot has broken free from a sand dune.

On Saturday, the science team reported that Opportunity had popped out of the trench it had dug itself into more than a month earlier.

"After a nerve-wracking month of hard work, the rover team is both elated and relieved to finally see our wheels sitting on top of the sand instead of half-buried in it," Jeffrey Biesadecki, a rover mobility engineer at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a news release.

Team members gathered at a Sunday barbecue to celebrate the breakthrough, and were back in their offices on Monday to plot out the next moves.

The two top tasks are to study the characteristics of the troublesome sand drift in Meridiani Planum and to develop safety-conscious procedures for the road ahead, said Jim Erickson, rover project manager.

"In the event that we get into these kinds of drifts, we want to be able to drive reliably," he told Monday.

Planning Opportunity's itinerary
Opportunity will probably circle around — "gingerly," Erickson said — and take a close look at the dune where it got stuck, using its camera-equipped robotic arm as well as its thermal imager, which apparently is back in working order after some earlier glitches.

The mission team wants to figure out whether the rover became mired because of the composition and the height of the dust in the dune, or because it sank into crust that was thinner than usual, or because "the topography just had a particular shape that gave us trouble driving on it," Erickson said.

"We're probably not going to go very far. ... It depends on how paranoid we are about approaching back to the area we just left," he said.

Planners are also considering a new type of zigzag driving to get across the dune field, Erickson said. Opportunity would drive a short distance in one direction, turn slightly to the right, verify that it won't get stuck, then drive another short distance, turn to the left, and repeat.

"It'll take a lot longer to drive large distances," Erickson said. "With this technique, we'll never break the 220-meter [single-day] record for distance, but we don't want to."

The rover's next destination is a bright patch of ground to the south, nicknamed Erebus Highway. Erickson and other rover team members hope that the "highway" is a stretch of rocky material leading to a wide crater also called Erebus.

"We're much more comfortable about driving on rocks," he said.

500-day mission
Erickson noted that Opportunity is approaching its 500th Martian day of operations — and Spirit, its twin on the other side of the Red Planet, already has passed the 500-day mark. Not bad, considering that the rovers' "warranty period" ran out after 90 days.

The rover team has worked around glitches with a stuck heater and a flaky steering motor actuator on Opportunity, as well as a balky drive motor and a worn-down rock drill on Spirit. "So far we've always gotten in and gotten out," Erickson said.

While the rover team was considering Opportunity's next moves, Spirit was keeping busy investigating the geology of the Columbia Hills in Gusev Crater. Cornell astronomer Steve Squyres, the principal investigator for the rover missions, reported on Saturday that Spirit had come across a nearby rock worthy of further investigation, nicknamed Backstay.

"It's a loose rock, not bedrock, so it may be a piece of impact ejecta from someplace far away," Squyres said in his mission update.

Even though the rovers already have sent back far more scientific data than expected, the scientists and engineers at JPL are greedy for more — and that's why the rover team worked through weekends and holidays to get Opportunity moving again, Erickson said.

The original twin-rover mission cost $820 million, and mission extensions have been budgeted at roughly $2.5 million per month. In April, NASA gave the go-ahead for extensions to continue as far ahead as September 2006.

"We paid to get this vehicle to Mars," Erickson observed. "At some point we will wear it out, and that's a good thing. Our goal in life is to wear it out. But bad things happen on Mars. ... The dust storm season is upon us, where you just might run out of time. Every day is precious."

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