NASA and rovers working overtime on Mars

By Guy Gugliotta
The Washington Post

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PASADENA, Calif. — The rovers have already made history. They landed safely on Mars, motored around its surface, photographed everything in sight and found evidence that today's rock-strewn wasteland once accommodated liquid water.

Pretty good. Now what?

That is the question scientists at NASA's Jet Propulsion Laboratory are asking this month as the two rovers, Spirit and Opportunity, complete the job they were sent to do. From now on, they are on overtime as they embark on extended forays expected to last until the middle of September — and perhaps beyond.

The extra mission begins May 1, but the transition is well under way. Planners have found $15 million in additional funding, started software upgrades for the rovers and put scientists on Earth time after three exhausting months of round-the-clock — Mars clock — staffing.

They have also chosen new targets to explore. After a mostly uneventful sojourn at Gusev Crater, Spirit is embarked on a 0.9-mile drive to a highland known as Columbia Hills, where planners hope to find rock outcrops that will provide new insights into Mars' geologic history.

Opportunity, meanwhile, has begun a 750-yard traverse to the edge of a crater dubbed Endurance. There scientists hope to find as much as 100 feet of exposed rock that could offer fresh clues about the extent of an ancient salt sea whose traces Opportunity discovered only a few yards from its landing site on Meridiani Planum.

If the crater shows promise, Opportunity's handlers may plunge in, even if the rover might never get out: "The rovers go down a lot better than they go up," said Flight System Manager Richard Cook.

"Will we take the bird in the hand? There will be a strong inclination to do that."

The major imponderable is how long the two rovers will function. The mission's 90-day design life ran out for Spirit on April 5 and will run out for Opportunity on April 26, but neither machine shows the slightest sign of slowing down, wearing out, losing communications, freezing to death, blowing an engine or otherwise falling apart.
 
Cook said engineers are keeping an eye on the solar arrays that charge the vehicles' batteries. During the first part of the mission, charging capacity declined by 0.13 percent per day because of dust accumulating on the array panels.

Planners are also carefully monitoring wear on the electric motors that do everything from turning the rovers' wheels to aiming their high-gain radio antennas. Cook said engineers in premission tests "qualified" the motors for 10 million revolutions, and so far, no rover motor has run for more than 2-1/2 million revolutions.

In the end, however, experts suspect the rovers will succumb to the stresses wrought by martian temperature fluctuations.

Daily temperatures for the rovers now swing between 133 degrees below zero to 1 degree Fahrenheit.

"You take a paper clip and bend it back and forth," said Firouz Michael Naderi, manager of NASA's Mars Exploration Program. "Eventually it breaks."

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