Out of Place Hemisphere Anomaly on Mars Rover Photo

A photograph taken by the Opportunity Mars Rover shows an object like half of a sphere and it looks like it is floating.

The object looks out of place and seems to be reflecting the immediate surroundings. I don’t know what it is, but if it is a rock then it is certainly very unusual in shape.

Given the clear markings of the top soil it appears the rover spent a fair amount of time excavating the general area around the object before the image of the object was taken.