Huge dust storm threatens NASA rovers on Mars

By Will Dunham

WASHINGTON (Reuters) - A dust storm raging on Mars presents the worst threat to date to the continued operation of NASA's two rovers, threatening to starve the solar-powered robots by blocking out sunlight, NASA said on Friday.

The little, six-wheeled rovers, Opportunity and Spirit, are operating at two distant sites just south of the Martian equator. The large regional dust storm that has lasted almost a month has been worse at Opportunity's locale, NASA said.

In an effort to protect the rovers from power loss that has the potential to leave one or both permanently disabled, the U.S. space agency has been scaling back their functions to the bare minimum, leaving them in near-dormant states.

"What we have the rovers do is wake up in the morning briefly, configure some necessary parameters for the day and then go back to sleep," John Callas, rover project manager at NASA's Jet Propulsion Laboratory in Pasadena, California, said in a telephone interview.

"And that's all they're doing. We do have them communicating (with Earth) about every three days," he added.

The rovers are not being buffeted by winds, but high-altitude fine particle dust has blocked 99 percent of direct sunlight needed to energize the rovers, officials said.

"The threat to the rover is that it doesn't have the energy to stay warm and that its sensitive electronics would become too cold. Things would get so cold that something would break inside the electronics," Callas said.

The rovers have electric heaters to prevent vital core electronics from getting too cold. One concern is that absence of sunlight could make the rovers drain their batteries.

That worst-case scenario is still weeks off at a minimum, Callas added. He said that because it was now Martian summer for the rovers, there was a chance temperatures would not fall low enough to ruin the electronics even if the rovers were starved of power.

'WE'RE ROOTING'

The dust storm is the biggest threat to the resilient rovers since they arrived on Mars in January 2004 for what was supposed to be a three-month mission, Callas said. It is the worst dust storm since their arrival, he added.

"We're rooting for our rovers to survive these storms, but they were never designed for conditions this intense," said Alan Stern, associate administrator of NASA's science office.

The rovers have gathered data about the geology of Mars, including evidence it once was a far wetter place that some scientists suspect may have been habitable by microbes.

Opportunity is about 130 feet from an entry point into Victoria Crater, which is about half a mile (800 meters) wide and was formed by a long-ago impact by a space rock on Martian surface.

The storm prompted NASA to put on hold plans to send the rover into the crater to examine rocks in its exposed walls.

"Not until the skies clear sufficiently and we have generous power margins would we consider driving the rover again and then entering the crater," Callas said.