Mars is the nearest planet to Earth after Venus, and it is the only planet to have either an atmosphere or a daytime temperature close to ours.
Mars is called the red planet because of its rusty red color. This comes from oxidized (rusted) iron in its soil.
Mars is the fourth planet out from the Sun, orbiting it at an average distance of 227.9 million km. It takes 687 days to complete its orbit.
Mars is 6786 km in diameter and spins round once every 24.62 hours – almost the same time as the Earth takes to rotate.
Mars’s volcano Olympus Mons is the biggest in the Solar System. It covers the same area as Ireland and is three times higher than Mount Everest.
In the 1880s American astronomer Percival Lowell was sure that the dark lines he saw on Mars’ surface through his telescope were canals built by Martians.
The Viking probes found no evidence of life on Mars, but the discovery of a possible fossil of a micro-organism in a Mars rock (see life) means the hunt for life on Mars is on. Future missions to the planet will hunt for life below its surface.
The evidence is growing that Mars was warmer and wetter in the past, although scientists cannot say how much water there was, or when and why it dried up.
Mars’ surface is cracked by a valley called the Vallis Marineris — so big it makes the Grand Canyon look tiny. 92 Planets
Mars has two tiny moons called Phobos and Deimos. Phobos is just 27 km across, while Deimos is just 15 km across and has so little gravity that you could reach escape velocity riding a bike up a ramp!
Mars is the best known planet besides Earth, studied by countless astronomers through powerful telescopes, scanned by orbiting space probes, and landed on more times than any other planet. All this effort has revealed a planet with a surface like a red, rocky desert — but there is also plenty of evidence that Mars wasn’t always so desert-like.
The 1997 Mars Pathfinder mission showed that many of the rocks on Mars’ surface were dumped in their positions by a huge flood at least two billion years ago. 93 Pavonis Mons volcano Arsia Mons volcano Ascraeus Mons volcano
In the 1970s the US Vikings 1 and 2 and the Soviet Mars 3 and 5 probes all reached the surface of Mars. Mars 3 was the first probe to make a soft landing on Mars, on 2 December 1971, and sent back data for 20 seconds before it unexpectedly fell silent. Viking 1 sent back the first colour pictures from Mars, on 26 July 1976. The aim of the Viking missions was to find signs of life, but there were none. Even so, the Viking landers sent back plenty of information about the geology and atmosphere of Mars. On 4 July 1997, the US Mars Pathfinder probe arrived on Mars and at once began beaming back ‘live’ TV pictures from the planet’s surface. Mars Pathfinder used air bags to cushion its landing on the planet’s surface. Two days after the Pathfinder landed, it sent out a wheeled robot vehicle called the Sojourner to survey the surrounding area. The Sojourner showed a rock-sterwn plain which looks as if it were once swept by floods. Pathfinder and Sojourner operated for 83 days and took more than 16,000 photos. Missions to Mars early in the 21st century may include the first return flight after 2010.