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30th Anniversary of The Planetary Society
  

Space Topics

Mars


Mars, the fourth planet from the Sun, is more like Earth than any other body in our solar system. It has mountains and valleys, polar ice caps, and dry riverbeds. It has seasons, an atmosphere with clouds, winds and dust storms, and a solid rocky surface. Its days and seasons are similar. Compared to all the other known planets besides our own, Mars also has a moderate climate -- summertime temperatures at the Martian equator during the daytime are comparable to those of winter in Antarctica! For these reasons, Mars is one of the few places in the solar system that humans can think realistically about exploring on foot.

The differences between Mars and Earth, however, are many. Mars is only half as large as our planet. Its thin atmosphere is comprised of about 95 percent carbon dioxide. The sunlight that reaches Mars is only about half as intense as that on this planet. Its two moons, Phobos and Deimos, are tiny little rocks. Its many volcanoes seem extinct, and its riverbeds dry. Is Mars a dead world, with an interesting past, but a dull future? Or does Mars have more surprises in store for us?

Mars is currently being explored by a fleet of spacecraft: Mars Exploration Rovers Spirit and Opportunity, 2001 Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter.

Mars Numbers
Size: 7th largest planet - 6,794 kilometers - 0.533 Earths
Orbit: 227,920,000 kilometers - 1.524 Earth orbits
Axial tilt: 25.19 degrees (only 1.74 degrees more than Earth's)
Number of moons: 2