Mars (Courtesy to Microsoft Encarta for this photograph.)

People have always gazed at Mars and other planets and stars in the sky, but about one hundred years ago astronomers thought that they saw straight lines in the surface of Mars. Because straight lines were only made by intelligent life forms, they were thought to be canals. These canals were seen to be lead straight from the polar ice caps at the northern and southern areas of Mars. As Mars goes through its various seasons, its ice caps melt during different times. These canals were thought to collect the water and then brought down to the equator. Later missions to Mars found that there were no lines, but they found a whole new world to explore.

Mariner 9 and later Viking missions discovered that Mars is very similar to Earth. For example, other than Earth, Mars is the only Inner Planet that has moons. Mars has two asteroid-like moons named Phobos (13 miles) and Deimos (7.5 miles). Scientists think that early in Mars' history, these two asteroids were attracted by Mars' gravity and went into orbit around Mars. Also Mars might have water and Mars is filled with canyons, mountains, volcanoes, and other land formations. The Solar System's largest volcano is found on Mars. It is known as Olympus Mons and is twice as tall as Mount Everest. Olmpus Mons is located on the Tharsis Plateau, a plateau that would cover from New York to Los Angeles. On the east side of the Tharsis Plateau, a rift valley called the Valles Marineris starts. It circles around one-third of Mars' surface. Just one of the branches of the rift valley is as large as the Grand Canyon in Arizona.