Magnified view of the surface of the rock known as "Block Island", on the surface of Mars. The image was taken by the microscopic imager onboard NASA's Mars Exploration Rover Opportunity during the 1,963rd Martian day, or sol, of the rover's mission on Mars (1 August, 2009). The triangular pattern of small ridges seen at the upper right is characteristic of iron-nickel meteorites found on Earth. Block Island has been identified as an iron-nickel meteorite based on this surface texture and analysis of its composition by Opportunity's alpha particle X-ray spectrometer. At about 60 centimetres (2 feet) across, it is the largest meteorite yet found on Mars.
NASA / JPL-Caltech / Cornell University / USGS