Martian rock 'Mimi'. This rock (centre) was examined by the Mars Exploration Rover Spirit on 14 February 2004, as possible evidence for water on Mars. Mimi, which is in an area of the Gusev Crater named Stone Council, looks very different from other rocks seen so far. It has a flaky appearance that may have been caused by one of several geological processes. The rock could have been formed by pressure from overlying rocks, or due to a meteorite impact. Alternatively, it could have been part of a sandy dune that was cemented into layers, a process that may have involved water. Photographed by Spirit's panoramic camera.