This approximate true-color image suggests that the plains beyond the small crater where the Mars Exploration Rover Opportunity now sits are littered with the same dark grey material found inside the crater in the form of spherules or "blueberries." Because Mars orbiters have observed the iron-bearing mineral hematite across these plains, scientists hypothesize that the blueberries are also made up of this mineral. This image was taken by the rover's panoramic camera on the 17th martian day, or sol, of its mission. Data from the camera's red, green and blue filters were combined to create this image.
Image credit: NASA/JPL/Cornell