Here are the main facts and figures about our red-orange neighbour:
Orbit: 227.9 million kilometres mean distance from the Sun, about half as much again as the distance between the Sun and Earth.
Diameter: 6794km. By comparison, Earth’s diameter is 12,756km, so Mars about half the size of our planet.
Martian day: 24 hours 37 minutes and 22 seconds.
Martian year: 669 martian days (687 Earth days).
Temperature: Mars is much colder than Earth. Average:
-55C (-67F). Minimum: -133C (-207.4F), at the poles in winter. Maximum temperature: 27C (80.6F) in summer on equator.
Atmosphere: Unbreathable for us humans. Composition 95.32% carbon dioxide (CO2), 2.7% nitrogen, 1.6% argon, 0.13% oxygen. Pressure at surface is less than 1/100th Earth’s atmospheric pressure.
Landscape: Rocky, dusty and dry, although some scientists speculate water lurks close to surface. Northern hemisphere is smooth and flat, southern hemisphere is deeply cratered, rugged highlands. North pole has a large, permanent cap of what is believed to be mainly water ice. South pole has a small cap, which may be frozen carbon dioxide (CO2) and almost disappears during the Martian summer.
Major features: Olympus Mons, at 26,000 metres, the highest known volcano in the solar system; Tharsis Dome, a mysterious bulge 10km high and 4000km across; Valles Marineris, a canyon 4000km long and up to seven kilometres deep.
Moons: Phobos, diameter 22km, orbit 5981km from surface; Deimos, diameter 12km, orbit 20,062km from surface.