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"
Unusual Bright Soil on Mars
06/04/2006
What is this bright soil on Mars? Several times while rolling across Mars, the treads of the robotic rover Spirit have serendipitously uncovered unusually bright soil. Spirit uncovered another batch unexpectedly last month while rolling toward its winter hibernation location on McCool Hill. The physics and chemistry instruments on Spirit have determined the soil, shown above, contains a high content of salts including iron-bearing sulfates. A leading hypothesis holds that these salts record the presence of past water, with the salts becoming concentrated as the water evaporated.