Volume: 03, Issue: 07 04/06/2005 
This image features Opportunity's heat shield impact site south of "Endurance Crater.” Image courtesy NASA/JPL/Cornell.
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Opportunity set a one-day distance record for martian driving on its 383rd martian day, or sol, which began Feb. 19, 2005. Opportunity rolled 582 feet across the plain of Meridiani on that sol. Image courtesy NASA/JPL.
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Spirit used its navigation camera to take the images combined into this 360-degree view of its surroundings near "Cumberland Ridge." Image courtesy NASA/JPL.
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Other Articles in This Issue:
Space Shuttle Discovery Moves to Launch Pad
Deep Impact Cruises toward Comet
Northern Lights and Southern Lights Are Not Mirror Images
Enhance Your Teaching Skills Online
 

Spirit and Opportunity Head for Triple Overtime

After easily surpassing their prime mission periods and first extended mission period, NASA’s Mars Exploration Rovers have been assigned another overtime project. NASA has approved up to 18 more months of operations for Spirit and Opportunity, which have already surprised engineers and scientists by continuing active exploration for more than 14 months.

"The rovers have proven their value with major discoveries about ancient watery environments on Mars that might have harbored life," said Dr. Ghassem Asrar, deputy associate administrator for NASA's Science Mission Directorate. "We are extending their mission through September 2006 to take advantage of having such capable resources still healthy and in excellent position to continue their adventures."

The rovers touched down on the Red Planet in January 2005. They have already completed 11 months of extensions on top of their successful three-month prime missions.

”[R]ight now, both rovers are in amazingly good shape,” said Jim Erickson, rover project manager at NASA's Jet Propulsion Laboratory. “We're going to work them hard to get as much benefit from them as we can, for as long as they are capable of producing worthwhile science results."

Opportunity is currently within a few football fields' length of a region called "Etched Terrain." There scientists hope to find rocks exposed by gentle wind erosion rather than by disruptive cratering impacts, as well as rocks from a different time in Mars' history than any examined so far.

To reach Etched Terrain, rover planners have been pushing the rover fast. Opportunity has overtaken Spirit in total distance driven, rolling more than three miles -- eight times the original goal. On March 20, Opportunity also set a new martian record of 722 feet in a single day's drive. Drive-distance estimates can vary by a few percent. The long drives take advantage of crossing a plain so smooth it's "like an East Coast beach," said JPL's Jeff Favretto, mission manager on the Opportunity shift in recent weeks. Also, Opportunity's solar panels, though now dustier than Spirit's, still generate enough power to allow driving for more than three hours on some days.

Spirit is in much rougher terrain than Opportunity, climbing a rocky slope toward the top of "Husband Hill." However, with a boost in power from wind cleaning its solar panels on March 9 and with its formerly balky right-front wheel now working normally, Spirit made some longer one-day drives last week than it had for months.

"We've doubled our power," said JPL's Emily Eelkema, mission manager. "It has given us extra hours of operations every day, so we can drive longer, and we've used more time for observations."

The jump in power output has taken some urgency out of Spirit's southward climb. With Mars now beginning southern-hemisphere spring, the sun is farther south in the sky each day. If not for panel-cleaning, Spirit might be facing the prospect of becoming critically short of power if still on the north-facing slope by early June.

"We still want to get to the summit of Husband Hill and then head down into the 'Inner Basin' on the other side," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the rover's science instruments. "But now we have more flexibility in how we carry out the plan. Before, it was climb or die."

Cresting the hill is now not as crucial for solar energy, but it still offers allures of potential exposures of rock layers not yet examined, plus a vista of surrounding terrain. In orbital images, the Inner Basin farther south appears to have terracing that hints of layered rock.

Both rovers do have some signs of wear and exposure. Spirit's rock abrasion tool shows indications that its grinding teeth might be worn away after exposing the interiors of five times more rock targets than its design goal of three rocks. Researchers probably won't know the extent of wear until Spirit's next rock-grinding attempt, which may be weeks away. Also, troubleshooting continues for determining whether Opportunity's miniature thermal emission spectrometer is still usable despite tests indicating a problem last month. All other instruments on both rovers are still working normally.

For more information about the rovers and their discoveries on the Internet, visit the following websites:
http://www.nasa.gov/vision/universe/solarsystem/mer_main.html
http://marsrovers.jpl.nasa.gov/home/index.html

    
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