Mineral pebbles on Mars. Close-up image of small spherules on the Martian surface near Fram Crater, photographed by the Opportunity rover. The area shown is 3 centimetres across. These objects, nicknamed blueberries , are haematite-rich concretions which provide further evidence for the presence of water in the ancient Martian environment. The Opportunity rover landed on Mars on 24 January 2004, and visited Fram crater during a journey from its landing site to a crater further east. This view comes from the microscopic imager on Opportunity's robotic arm, April 2004.