A phenomenon akin to a space-borne car wash has boosted the performance of one of the two NASA rovers probing the surface of Mars.
Layers of dust have been swept from the solar panels of the Mars Opportunity vehicle while it was closed down during the Martian night. The cleaning boosted the panels' power output close to their maximum 900 watt-hours per day, after at one stage dropping to 500 watt-hours because of the heavy Martian dirt.
"These exciting and unexplained cleaning events have kept Opportunity in really great shape," the London-based New Scientist magazine quoted NASA rover team leader Jim Erickson as saying.
The chief scientist for the rover missions, Cornell University's Steve Squyres, chuckled at the car wash reference. However, he acknowledged that Opportunity, unlike its twin Spirit rover on the other side of the Red Planet, has somehow been getting a thorough cleaning.
"Spirit’s pretty dirty," he told MSNBC.com. "Opportunity looks like it just came off the showroom floor. We do not understand the process well."
But alien-conspiracy theorists shouldn't get their hopes up quite yet.
"I think it's probably nothing much more mysterious than a few well-timed gusts of wind," Squyres said.
Even though Spirit's solar arrays are grimier, that rover "is actually doing very well, too," Squyres said. Its daily power output had at one point dropped to 380 watt-hours — close to the 280 watt-hours required to keep itself alive — but now the output was "well over 500 and trending upward," he said.
He said two factors were behind Spirit's resurgence: First of all, the depths of Martian winter have passed, and there are more hours of sunlight as spring approaches. Also, Spirit has been positioned to tilt northward on the north flank of Husband Hill.
"It tilts the arrays toward the sun, so that significantly improves the solar output," Squyres said.
Unless something goes awry, the rovers will begin their second year of operation on Mars in January — not bad, considering that the machines were built with a "warranty" lifetime of merely 90 days.