Space and Time
Size: Diameter 6792km
Mass: 6.42x10(exp23)kg
Composition: Small iron core
Mean temperature: -23 °c
Distance from Sun: 228 million km
Atmosphere/weather: Thin carbon dioxide atmosphere
Moon/satellites: Two
Orbital length: 687 days
Length of day: 24hours, 37 mins
Distance from Earth: Max 378 million km, min 78 million km
Mars is the fourth planet from the Sun. It is one of the brightest objects in the night sky to us on Earth. It is sometimes called the 'Red Planet' because of its red soil. It is red because it contains large amounts of iron oxide.
Mars is a small rocky body once thought to be very Earth-like. Like the other 'terrestrial' planets - Mercury, Venus, and Earth - its surface has been changed by volcanism, impacts from other bodies, movements of its crust and atmospheric effects such as dust storms. |
A view of the Martian surface taken from the Viking 1 spacecraft, which landed on Mars in 1976
Mars has polar ice caps that grow and recede with the change of seasons. Areas of layered soil near the Martian poles suggest that the planet's climate has changed more than once. This is possibly caused by a regular change in the planet's orbit. Martian tectonism - the formation and change of a planet's crust - differs from Earth's. Earth tectonics involve sliding plates that grind against each other or spread apart in the seafloors. Martian tectonics, however, seem to be vertical, with hot lava pushing upwards through the crust to the surface. Periodically, great dust storms engulf the entire planet. The effects of these storms are dramatic, including giant dunes, wind streaks and wind-carved features.
Olympus Mons, the largest volcanic mountain in the solar system
Scientists believe that 3.5 billion years ago, Mars experienced the largest known floods in the solar system. This water may even have pooled into lakes or shallow oceans. There is evidence of water erosion on the planet's surface. The source of this water and what happened to it is a mystery.
In 2002, scientists announced the discovery of a key piece in the puzzle: the Mars Odyssey spacecraft had detected large quantities of water ice close to the surface. The ice is mixed into the soil only a meter (about 3 feet) below the surface of a wide area near the Martian south pole.
Deimos
Mars has some remarkable geological characteristics. This includes the largest volcanic mountain in the solar system, Olympus Mons (27km high and 600km across). Volcanoes in the northern Tharsis region are so huge they deform the planet's roundness. There is also a gigantic equatorial rift valley, the Valles Marineris. This canyon system stretches a distance equivalent to the distance from New York to Los Angeles, right across North America. Arizona's Grand Canyon could easily fit into one of the side canyons of this great chasm.
Phobos
In January 2004, NASA landed two robots on Mars. These have sent back amazing images of the planet's surface, as well as carrying out important research into the geology of Mars. They may even discover if there wa ever any life on the now barren world. You can find out more about this mission on the NASA project web-pages [opens new window].
Mars also has two small moons, Phobos and Deimos. Although no one knows how they formed, they may be asteroids snared by Mars' gravity.
Mars is the Roman god of war (Ares in Greek legend). The planet probably got this name due to its red colour. The name of the month March derives from Mars. The two moons are named after the horses that pulled the chariot of Ares. Phobos means 'fear' and Deimos means 'panic'.
Images, information and videos courtesy of NASA.