"Mars keeps throwing stuff at us"
Ars Technica just reported that the Mars Rover had photographed a stone in its immediately vicinity that wasn't in the same space 12 (Martian) days earlier. It's showing its bottom side and looks like a jelly donut, with a reddish spot in the center. It could have come from some geological action but most likely was flipped out of its position, where it had been resting for several billion years, by passage of the Rover's wheels. A steering actuator that turns a wheel left or right is broken on Opportunity. When the vehicle turns, the wheel skids along the surface, possibly kicking up debris. "Mars keeps throwing stuff at us," said lead Rover scientist Steve Squyres of Cornell at a Rover anniversary event last week.