Stephen Green, age 13, of Watertown, N.Y., for his question:
WHY IS MARS CALLED THE `RED PLANET'?
Mars has been called the red planet because it has a reddish color. It was named by the ancient Romans after the bloody red god Mars.
If you were to study Mars through a telescope, you would discover that it has bright orange sections and darker, less red areas that change with the Martian seasons.
The reddish areas are a result of Mars' heavily oxidized, or rusted, surface. The dark sections are rocks much like basalts that have been weathered and oxidized.
The bright sections of the Martian surface appear to be similar to the dark but even more oxidized and weathered.
Scientists also tell us there is evidence of much fine, dust sized bits of material on the Martian surface.
Bright caps apparently made of ice can be seen at Mars' polar areas. Each autumn, bright clouds develop over the appropriate pole and they dissipate in spring. The cap gradually recedes as summer sunlight evaporates part of the frost. The following autumn the frost builds up again.
Three types of clouds can be seen on Mars: pink clouds of dust, thin blue clouds of ice crystals and white clouds thought to be water vapor.
At its closest approach to the earth, Mars is 35 million miles away. Venus is the only planet that comes closer. Mars has a diameter of about 4,200 miles, which is a little over half that of the earth.
Mars has two moons: Phobos and Deimos. Each is heavily cratered and appears to have been caught by Mars early in its history. Both moons are small: Phobos is 13 mi„Les across while Deimos is only about 7.5 miles.
Scientists tell us that the surface conditions found on Mars are more like the conditions found on earth than any other planet But, even so, our planet and animals wouldn't be able to live on Mars because of the cold temperatures and thin atmosphere. The atmosphere on the red planet is 95 percent carbon dioxide, 2.7 percent nitrogen and 1.6 percent argon with traces of oxygen and water.
Between 1964 and 1976 six missions were carried out by unmanned spacecraft from the United States. Mariner IV gave us our first close view of Mars in 1964. In 1969 Mariner VI and Mariner VII came to within 2,000 miles of the planet.
Mariner IX was the first Mars orbiter. In 1971 and 1972 it circled Mars at a distance of about 1,000 miles. It sent back details of Martian dust storms, information on the planet's surface and fine pictures of the two moons.
Viking I landed on Mars on July 20, 1976. It selected a desertlike section near the planet's equator. On Sept. 3 the same year, Viking II landed a bit farther north. Both craft sent back excellent pictures of Mars' surface. The two Viking missions also sent back information on Mars' atmosphere and soil. There was no proof returned from Mars that there is life on the red planet.
For the latest information on Mars go to the JPL internet site.