MARS APPEARS PALE ORANGE IN THE NIGHT SKY. The Babylonians, Greeks, and Romans all named it after their gods of war. In reality Mars is a small planet-only half the size of Earth-but there are similarities. Mars, like Earth, has a 24-hour day, polar caps, and an atmosphere. Not surprisingly, Mars has always been the most popular candidate as a site for possible extraterrestrial life. Many scientists believe that some form of life - or at least evidence of past life - may remain within the planet, but no life could survive on the surface. The atmosphere is too thin to block out deadly ultraviolet rays. Mars is also farther from the Sun than Earth, making it much colder

AROUND THE PLANET MARS The Martian atmosphere is much thinner than that of Earth and is composed mostly of carbon dioxide. There is enough water vapor for occasional mist, fog, and clouds to form. Manner 9, the first spacecraft to orbit Mars, revealed a series of winding valleys in the Chryse region that could be dried-up river beds. Mars also has large volcanoes. One of them - Olympus is the largest in the solar system. There are also deserts, canyons, and polar ice caps Mars resembles a desert. Winds whip up the red dust and it becomes suspended in the atmosphere, giving the sky a reddish hue.

MARTIAN MOONS: Mars has two small moons, Phobos and Deimos, 28 and 16 km in diameter. Since the orbit of Deimos is only 14,580 miles (23,460 km) from the center of Mars, it will probably be pulled down to the surface with a crash in about 50 million years.