As NASA's Mars rovers keep rolling past all expectations of their useful lives, scientists have a happy mystery: For some reason one of the vehicles has actually gained power recently.
Opportunity recently experienced an unexplained rejuvenation from what can so far be described only as two or three significant "cleaning events," said Jim Erickson, the rover project manager at NASA's Jet Propulsion Laboratory in Pasadena.
"Now we're assuming they're cleaning, but all we can really say is that overnight the solar panels produced between 2 and 5 per cent additional power immediately," he said.
"We're surmising that for some reason dust is being removed from the solar panel and that's increasing the efficiency of the sunlight being converted to electricity."