The rock suddenly appeared on photographs taken by Opportunity Mars rover on Sol (Martian day) 3540 or January 8 Earth time, according to NASA’s website.
The rock that appears to be missing in a earlier Opportunity panoramic camera SOL 3536 Photo appears in a later SOL Photo 3540.
The discovery sparked debate among bloggers with various suggestions of the rock’s origin. Among some of the suggestions was the theory that it’s a meteorite, and it literally fell from the sky and landed next to the rover. More believable theories said the rock was something kicked up by Opportunity on its Sol 3540 turn.
But is it a rock? Here is an extreme close up of a part of the rock -- Living Fossil?
Link to Sol 3540
Link to Sol 3536