Martian soil. Micrograph of a patch of soil on Mars. This was taken by the microscopic imager instrument on the Mars Exploration Rover Spirit after it left its lander on 18 January 2004. The upper left corner is illuminated by direct sunlight. At first, scientists thought that the soil was dust-like, but investigations showed that it hardly moved when pressed. Scientists will use equipment on board Spirit to further investigate the texture of the soil. They will also analyse the composition of Martian rocks in a search for evidence of water on the planet. Magnification: x3.3 when printed 10cm wide.