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MARS

Mars

Equatorial Radius3,393.4 km
Mean Density3.94 g/cm³
Sidereal Rotation24h37m22.662s
Sidereal Period686.95 days (1.88 years)

Sidereal Rotation=One full rotation(1 Earth day) / Sidereal Period=One revolution around the Sun

Mars has the largest known volcano in the solar system - Olympus Mons. Olympus Mons measures 600 km (372 miles) at the base and 25 km (15 miles) high. Just for comparison, Mount Everest is 8.85 km (5.5 miles) high. That means that Olympus Mons is approximately 3 time taller than Mount Everest. Another finding on Mars was a canyon that would stretch the entire length of the United States. This canyon, Calles Marineris, measures nearly 5000 km (3100 miles) in length. These discoveries were made by Mariner 9 in 1971.

Mars has seasons just as the Earth does, well almost. The temperatures on Mars range from -190°F to just over 80°F. During the Martian summers, the polar ice cap melts leaving only a small patch of ice. The ice caps were believed to be frozen carbon dioxide, or dry ice, but further studies have shown that the polar ice caps also contain water ice. This means that Earth is NOT the only planet in the solar system with water. The polar ice caps could be water ice covered by a layer of dry ice. Further studies are needed...GO Mars Lander!!!
Mars has two satellites, Phobos and Deimos.
PhobosPhobos has a crater measuring nearly 8 km across at one end of it that almost split this satellite into pieces.
DeimosDeimos is the larger of the two and is also heavily marked with craters, though not as drastic as Phobos.