NASA Mars: Rover Opportunity Image of Chocolate Hills rock

Picture: AFP / NASA / JPL

The Chocolate Hills rock on Mars. NASA's Mars Exploration Rover Opportunity took the image showing a strange coating that one researcher has called a "blueberry sandwich."

The coating appears blue because of the false-colour effect used to highlight details

Image Credit: NASA/JPL-Caltech/Cornell University

Opportunity's microscopic imager took this detail view of the coating on "Chocolate Hills," on which a layer of peppercorn-size spheres nicknamed "blueberries" are packed densely.