On Thursday NASA JPL held the Mars Exploration Rover 10-Year Anniversary Event to celebrate the 10 years of exploring Mars with the Opportunity, Spirit, and Curiosity rovers.
During the event Steve Squyres of Cornell showed this intriguing comparison of two images of the same spot near the Opportunity rover : Mystery Rock ‘Appears’ in Front of Mars Rover – Space.com
Credit: NASA/JPL-Caltech
Before you start believing in rock throwing Martians, this is most likely a piece of debris kicked up by one of the rover’s wheels.