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Mars is the fourth planet from the sun at about 228 million-km (141 million miles) and the last terrestrial planet from the sun. The next five planets in order from the sun are gaseous. Mars follows closely behind Earth but is comparatively smaller, with about h ....

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.... southern hemisphere is strewn with ancient craters of all sizes and is also elevated by a several kilometers creating a visible boundary. On the opposite end the northern hemisphere consists of a wider variety of geological features, but is obviously smoother and much younger. There are large volcanoes, a great rift valley, and a variety of channels. Volcanism is a geological process that occurs on Earth today, and has on many planetary bodies throughout the history of the solar system. No volcanism is occurring on the surface of Mars today. In the past, however, volcanism was one of the main forces creating and reshaping the surface of the plane ....