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Explorations of the Universe. Mars. Mars. About half the size of Earth Rotates in 24.5 hours Ranges from 207 to 249 million km (129 to 155 million miles) from Sun Period: 687 days Two tiny satellites. The Surface of Mars. Thin carbon dioxide atmosphere about 1/150 as dense as Earth’s
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Mars • About half the size of Earth • Rotates in 24.5 hours • Ranges from 207 to 249 million km (129 to 155 million miles) from Sun • Period: 687 days • Two tiny satellites
The Surface of Mars • Thin carbon dioxide atmosphere about 1/150 as dense as Earth’s • Surface temperatures -20 to -200 C • Polar caps of ice and frozen carbon dioxide • Large rift valley (Vallis Marineris) • Huge Shield Volcanoes (Olympus Mons) • Evidence for former liquid water
Modern Imaging Technology Improves Earth-Based Views of Mars Greatly
How to Lose an Ocean • If water is exposed to solar UV and particles, it breaks down to H + O (photo-dissociation) • Happens if water gets into upper atmosphere • Planet gets hot (Venus) • Planet loses atmosphere (Mars) • Oxygen combines with iron and other elements, on Mars may also have escaped