A northern portion of the rim of Endeavour Crater is visible on the horizon of this image taken by the panoramic camera on NASA's Mars Exploration Rover Opportunity on March 7, 2009.
updated 3/18/2009 6:45:57 PM ET 2009-03-18T22:45:57

The panoramic camera on NASA's Mars rover Opportunity has caught a first glimpse on the horizon of the uplifted rim of the big crater that has been Opportunity's long-term destination for six months.

Opportunity's twin, Spirit, also has a challenging destination, and last week switched to a different route for making progress to it.

Endeavour Crater, 14 miles in diameter, is still 7 miles away from Opportunity as the crow flies, and at least 30 percent farther away on routes mapped for evading hazards on the plain.

"We can now see our landfall on the horizon. It's far away, but we can anticipate seeing it gradually look larger and larger as we get closer to Endeavour," said Steve Squyres of Cornell University, and the principal investigator for the rovers' science instruments. "We had a similar experience during the early months of the mission watching the Columbia Hills get bigger in the images from Spirit as Spirit drove toward them."

Opportunity has already driven about 2 miles (3.2 kilometers) since it climbed out of Victoria Crater last August after two years of studying Victoria, which is less than one-twentieth the size of Endeavour.

"It's exciting to see our destination, even if we can't be certain whether we'll ever get all the way there," said rover project manager John Callas of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "At the pace we've made since leaving Victoria, the rest of the trek will take more than a Martian year." A Martian year lasts about 23 Earth months.

Both rovers landed on Mars in January 2004 to begin missions designed to last for three months. Both are still active after more than five years.

For the next several days, the rover team plans to have Opportunity use the tools on its robotic arm to examine soil and rock at an outcrop along the route the rover is taking toward Endeavour.

"We're stopping to taste the terrain at intervals along our route so that we can watch for trends in the composition of the soil and bedrock," Squyres said. "It's part of systematic exploration."

The pause also gives Opportunity a chance to rest its right-front wheel, which has been drawing more electric current than usual, an indication of friction within the wheel. This strategy has worked in the past.

Also, on March 7, the rover did not complete the backwards-driving portion of its commanded drive due to unanticipated interaction between the day's driving commands and onboard testing of capabilities for a future drive. The team is analyzing that interaction before it will resume use of Opportunity's autonomous-driving capabilities.

Meanwhile, on March 10, the rover team decided to end efforts to drive Spirit around the northeastern corner of a low plateau called "Home Plate" in the inner basin of the Columbia Hills, on the other side of Mars from Opportunity. Spirit has had the use of only five wheels since its right-front wheel stopped working in 2006. Consequently, it usually drives backwards, dragging that wheel, so it can no longer climb steep slopes.

"After several attempts to drive up-slope in loose material to get around the northeast corner of Home Plate, the team judged that route to be impassable," Callas said.

The new route to get toward science targets south of Home Plate is to go around the west side of the plateau, though even it could prove tricky.

"The western route is by no means a slam dunk. It is unexplored territory. There are no rover tracks on that side of Home Plate like there are on the eastern side," Squyres said. "But that also makes it an appealing place to explore. Every time we've gone someplace new with Spirit since we got into the hills, we've found surprises."

NASA has successfully commanded the Mars Odyssey spacecraft to reboot its computer.

Mission manager Gaylon McSmith of NASA's Jet Propulsion Laboratory said the restart on Wednesday went without a hitch.

Scientists wanted to reboot the computer because they're worried that its memory may have been corrupted from years of exposure to space radiation. The spacecraft has been orbiting Mars since 2001.

McSmith says the procedure also restored the spacecraft's backup systems. Engineers hadn't been sure those would work because a power component had become inoperable.

The reboot was delayed a day after engineers noticed a temperature spike. An investigation revealed that a heater circuit was temporarily stuck in the "on" position. The heater was turned off in advance of the reboot.

The Odyssey orbiter can resume operations after several days. Its best-known instrument is the Thermal Emission Imaging System, or THEMIS for short. THEMIS and other instruments on the spacecraft have helped researchers identify huge reservoirs of water ice on the Red Planet.

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