Martian rock research. Holes drilled and photographed by the Mars Exploration Rover 'Opportunity'. Image of seven holes in a crater on Mars (centre, continuing towards top). Opportunity's Rock Abrasion Tool, RAT, was used to drill 4.5 centimetre diameter holes in Martian rock to obtain geological information. The tailings around the holes show evidence for red haematite. Photographed looking towards the rim of Endurance Crater, Mars.