Monday, March 05, 2007


Mars is the fourth planet from the Sun and is known as the Red Planet due to its reddish look as seen from Earth. The planet is named after Mars, the Roman god of war. A terrestrial planet, Mars has a thin atmosphere and surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of Earth. It has the peak mountain in the solar system, Olympus Mons and the largest canyon, Valles Marineris. Mars' turning period and seasonal cycles are also related to those of the Earth.
Mars has two tiny natural moons, Phobos and Deimos, which orbit very close to the planet and are attention to be captured asteroids.
Both satellites were discovered in 1877 by Asaph Hall, and are named after the characters Phobos (panic/fear) and Deimos (terror/dread) who, in Greek mythology, accompanied their father Ares, god of war, into battle. Ares was known as Mars to the Romans.
From the surface of Mars, the motions of Phobos and Deimos appear very different from that of our own moon. Phobos rises in the west, sets in the east, and rises another time in just 11 hours. Deimos, being only just outside synchronous orbit—where the orbital period would match the planet's period of rotation—rises as expected in the east but very slowly. Despite the 30 hour orbit of Deimos, it takes 2.7 days to set in the west as it slowly falls behind the rotation of Mars, then just as long once more to rise.
Because Phobos' orbit is under synchronous altitude, the tidal forces from the planet Mars are slowly lowering its orbit. In about 50 million years it will either crash into Mars' surface or break up into a ring structure around Mars.

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