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
22/10/2007

Scroll right to see the largest crater yet visited by a rover on Mars. Reaching the expansive Victoria Crater has been a goal for the robotic Opportunity rover rolling across Mars for the past two years. Victoria crater has about five times the diameter of Endurance Crater, which Opportunity spent six months exploring. Opportunity reached Victoria last year, and was cautiously probing the edges of the stadium-sized crevice while waiting for large dust storms to clear. A safe path was found, and Opportunity has slowly entered into Victoria Crater. It is hoped that Victoria Crater will show a deep stack of layers uncovered by the initial impact, and hence new clues into the ancient surface history of Mars. Visible in the distance in the above mosaic is the far rim of Victoria Crater, lying about 800 meters away and rising about 70 meters above the crater floor. The alcove in front has been dubbed Duck Bay. A new APOD RSS feed is available here, or from the link line below.