You probably haven’t heard much about them recently, but those little Rovers are still going strong. Eighteen months after they touched down on the surface of Mars. A Martian day is known as a ‘sol’ and so far these robots have soldiered on, way passed their expected ‘Use By’ date. Opportunity is 434 sols over her ‘warranty’ and Spirit is 454 beyond hers. Powered by solar arrays utilising triple layer Gallium Arsenides solar cells, the Rovers have survived much longer than their earthbound team ever imagined. Aided in part by the Martian windstorms, which remove accumulated dust from the surface of the panels. The solar arrays were initially able to produce about 900 watt-hours of energy per martian day, or sol, charging two 8-amp-hour lithium batteries. Even now they can still manage 410 watt-hours per martian sol. Even though these sun driven vehicles have proven robust beyond anyone’s wildest dreams, it seems the next Rovers might be nuclear powered. Progress, huh? Get more technical guff over at the Jet Propulsion Lab. Or, for a neat little backgrounder, try the online copy of the July 05 issue of ::National Geographic.