Mars
The fourth and the outermost rocky planet from the Sun, Mars is also called the red planet. Mars' surface contains abundant quantity of iron. The dampness and warmth in the atmosphere caused the rusting of iron. The rusted iron and the dusty red soil in the surface give reddish colour to the planet. The blood-red colour of Mars resembles war and so it was given the name of Mars, the Roman god of wars. Due to the residues of dust particles in the atmosphere the sky of Mars looks pink in colour. The atmosphere of Mars is much thinner than the Earth's, with icy caps at the north and south poles. Only a few clouds and morning mists can be seen. The atmosphere mainly contains carbon dioxide. It also contains small amount of water vapour, oxygen, nitrogen, carbon monoxide, neon, argon, xenon and krypton. Mars has many plains formed of volcanic lava, large craters, basins, channels, canyons and huge volcanoes. Olympus Mons, which is 25 kilometres high and 600 kilometres in diameter is the largest known volcano in the Solar System. The canyons were formed by the movements of the surface crest. The Valles Marineris is an enormous canyon system that stretches for about 4000 kilometres along the surface of the planet. Mars takes 687 earth days to revolve round the Sun and 24 hours and 37 minutes to rotate on its axis, which tilts 24° from the perpendicular. In the 19th century astronomers believed that there were signs of life on Mars. Later it has been proved that the canals and dark patches found out there, are optical illusions and blown off dust that covered the planet. The channels in Mars show that there was abundance of flowing water millions of years ago and now dried up. Phobos and Deimos are the two satellites of Mars found out by an American astronomer Asaph Hall in 1877.
Flights to Mars
In 1965 Mariner-4 the US spacecraft sent photographs of the surface of Mars towards
the Earth. Mariner-4 and Mariner-9 transmitted photographs detecting the meteor craters on the surface of the planet. Viking-I and Viking-2 of US landed on Mars during the year 1976 and sent to Earth close-up photographs of the surface features of Mars.
Mars
Distance from the sun in km.: 227.9 million Diameter at equator in km.: 6796
Mass with respect to the earth: 0.107 (earth=1)
Gravity with respect to the earth: 0.38
Period of revolution: 687 earth days
Period of rotation: 24 hours and 37 minutes
Density (g/cm³): 3.94
Temperature:-143°C to 17°C
Satellites: 2
