Mars is the fourth of the Sun’s nine planets – the next in order from the Sun after Earth itself. It is the planet that most resembles Earth and although now dry, Mars was once probably awash with water. Mars has two tiny moons, Phobos and Deimos, which may be captured asteroids.
Key facts about Mars
Mean distance from Sun: 228,000,000 km/141,700,000 miles (1.524 AU)
Diameter: 6,792 km (4,220 miles)
Length of year: 687 days
Rotation period: 24 hr 37 min
Mean orbital velocity: 24.14 km/sec (15 miles/sec)
Key facts about Phobos
Mean radius: 11 km (6.8 miles)
Distance from Mars: 9,380 km (5,830 miles)
Period of Rotation: 0.3188 days
Key facts about Deimos
Mean radius: 6.2 km (3.9 miles)
Distance from Mars: 23,460 km (14,580 miles)
Period of rotation: 1.2625 days
Fun facts about Mars
Mars represented the god of war for the Vikings, the Greeks and the Romans. In Assyria, it was known as the “Shedder of Blood”.
The surface area of Mars is around the same as the land area of Earth. Its red colour is due to oxidised iron minerals in the surface rocks – in other words rust!
Mars was at its closest for centuries in 2003 and will not come as close again until 28 August 2287. But in 1924 it was only 12,500 miles (20,000 km) farther away.
Since 2003, a silly email has been doing the rounds warning that Mars will appear as big as the Moon in the sky. Ignore it!
English author Jonathan Swift eerily described the existence of two moons around Mars in his 1726 masterpiece Gulliver’s Travels – more than 150 years before Phobos and Deimos were discovered in 1877.
The idea of intelligent life on Mars inspired H G Wells to write his classic novel The War Of The Worlds.
Quick on the draw
As data slowly dribbled back from Mariner 4 as a stream of numbers, impatient NASA scientists used it to scribble out rough images of the pictures on a grid.
The string of failed missions to Mars in the 1980s and 1990s led wags to suggest that there was a jinx at work.
As well as the famous face, some have seen ancient monuments on Mars including pyramids on spaceprobe photos – but closer study reveals them to be tricks of the light like patterns in the clouds.
Olympus Mons is the largest volcano in the Solar System, standing 26km across and 600km across. By contrast Hawaii’s Mauna Loa is ‘only’ 8km high.
Several meteorites found on Earth have been identified as coming from Mars. Asteroid impacts millions of years ago blasted a lot of Mars rock into space. It floated around the Solar System before colliding with Earth 13,000 years ago.
Antarctica acts as a giant deep freeze, preserving meteorites that fall from space. Many have been found lying in the snow thousands of years after they fell.