MARS

Mars, the fourth planet from the Sun and neighbor to Earth, catches our interest and imagination in scientific fact and fiction. Long popular in novels and movies as home to a sophisticated civilization, recent images paint a truer, and perhaps more exciting, picture. Satellite views taken by the Mars Global Surveyor show dried gullies, which may indicate that Mars had streams and shallow seas millions of years ago. Since scientists consider water a key ingredient to the formation of life, possible signs of ancient water lead researchers to hunt for clues that microbial life, invisible to the human eye, may have once existed on the planet.

NASA's Mars Odyssey spacecraft, launched in April 2001, is on a mission to map the martian surface and learn about its minerals and elements, detect water and shallow buried ice, and study the radiation environment. The global mapping will provide information on the structure of the red planet and about the geological processes that have formed it.

Besides the significance of its surface elements, the small, rocky planet has some impressive geological features. It boasts the largest volcano in the solar system, Olympus Mons, which stands 25 km (16 miles) high and 624 km (374 miles) wide. A giant canyon, Valles Marineris, stretches a length close to the distance between Los Angeles and New York--4000 km (2500 miles) long and as deep as 7 km (4 miles).

Mean Distance from Sun	227,936,640 km (1.42 x 10⁸ miles) or 1.52 astronomical units
Diameter	6,794 km (4,221.6 miles)
Volume (Earth = 1)	0.149
Mass	6.42 x 10²³ kg (0.023 x 10²⁷ ounces) or 0.108 (Earth = 1)
Density	3.94 gm/cm³
Surface gravity	0.38 (Earth = 1)
Rotation period (length of day in Earth days)	1.026
Revolution period (length of year in Earth days)	686.98 (Earth days)
Mean surface temperature	-5.15 - -87.15 C (22.73 - -124.87° F)
Natural satellites	Phobos and Deimos

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