Mars
Mars is the fourth planet from the Sun and the seventh largest in the Solar System. A cold, dusty desert world with a thin atmosphere (mostly CO₂), the planet features extinct volcanoes, deep canyons, polar ice caps, and seasons. Mars has two small moons (Phobos and Deimos), a day just over 24 hours long, and a year lasting about 687 Earth days. It is a prime focus of robotic exploration and studies about past water and habitability.
Source: science.nasa.gov
APODs including "Mars"
A Close-Up of Martian Soil
18/01/2004
Make your background the closest image of Mars yet. The Spirit Rover currently rolling on Mars has taken the highest resolution image to date of another planet. The above black and white image spans only about 1.5 centimeters across, with details smaller than 1/10 of a millimeter visible. A microscope attached to the Spirit rover's instrument arm took the image. Up close, the Martian soil appears to planetary geologists to have clumping properties similar to cocoa powder. As more images come in and as the Spirit Rover continues to explore Mars, more information about the unusual floor of Gusev Crater are likely to emerge.