Mars is the fourth planet from the Sun. Of all the planets Mars is the most similar to the Earth. At one time, many people believed that extra-terrestrial life would be found there. It is also known as the red planet.
Mars is easily recognizable at first sight because of its red color. For this reason, it was associated with warfare by the Babylonians, the Greeks and the Romans; it is named after the Roman god of war. The planet has two small dark moons that are covered in craters. The satellites of Mars are called Deimos and Phobos. They were probably captured by the gravity of Mars.
Details of the surface of Mars are only visible through a telescope. It features white polar caps, dark spots and lines, which the Italian Schiaparelli described as canals in 1887. Mars is most clearly visible from Earth when it is directly opposite the Sun. This is known as the opposition and the planet is visible all night during such periods.
Mars has a diameter of 6786 kilometers. Its mean distance from the Sun is 227 million 600,000 kilometers. Because of its highly eccentric orbit the distance from the Earth varies between a minimum of 55,700,000 kilometers and a maximum of 399 million kilometers.
Temperatures on Mars range from minus 100 to plus 20┬░ Celsius. 95% of the atmosphere is made up of carbon dioxide, the remainder consisting of nitrogen, argon and traces of water vapor, carbon monoxide and other gases. It is one hundred times less dense than the Earth's atmosphere.
The northern polar cap consists of frozen water, the southern cap of frozen carbon dioxide. Great sandstorms, which are even visible from Earth as orange colored spots, sometimes occur on Mars. White clouds of water or carbon dioxide ice crystals can also be observed.
