This set of images shows the results from the rock abrasion tool from NASA's Mars Exploration Rover Opportunity (left) and the drill from NASA's Curiosity rover (right). Note how the rock grindings ... more 

This set of images shows the results from the rock abrasion tool from NASA's Mars Exploration Rover Opportunity (left) and the drill from NASA's Curiosity rover (right). Note how the rock grindings from Opportunity are brownish red, indicating less