The cleaning had 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.
By contrast, the power output of the solar panels of Mars Spirit - on a different part of the Red Planet - had dropped to just 400 watt-hours a day, clogged by the heavy dust.
"These exciting and unexplained cleaning events have kept Opportunity in really great shape," the magazine quoted Nasa rover team leader Jim Erickson as saying.
By the adventuress on Thursday, December 23, 2004
Something -- or someone -- is regularly cleaning the US space rover on Mars, Opportunity.