Mystery rock spotted on Mars - CNN.com

Did Mars rover Opportunity order a jelly doughnut?
Not quite, but scientists are baffled by a white rock with a dark red low spot in the middle that "just plain appeared at that spot" on the planet where the rover is situated, says Steve Squyres, lead scientist of the Mars Exploration Rover mission.
In recent weeks, Opportunity took photos of the same spot on Mars, 12 days apart. The rover's panoramic camera showed only barren bedrock on mission day 3528 (in Mars time), but on day 3540, a photo of the same scene revealed the mysterious, doughnut-shaped rock.
Heard this on the radio on the way to work this morning. Just had to have a google for it