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.