MARS: THE RED PLANET

The time it takes Mars to rotate once on its axis is called a Martian Day. It is about a half an hour longer than an Earth day. Mars' year , or the time it takes to revolve around the sun, is close to two Earth years long. Mars has two moons, Phobos and Deimos, which are named after the dogs of the Roman god Mars. They are tiny, heavily catered, dark chunks of rock. Some researchers and scientists believe that they might be asteroids captured by the gravitational pull of Mars. Phobos orbits Mars once in less than one Martian day, so it appears to rise in the west and set in the east, usually twice a day. Deimos has the more ordinary habit of rising in the east and setting in the west.

From Earth, Mars appears as a fairly bright, starlike object. It moves through Earth's sky rapidly. Mars appears to move backwards in the sky for a short time around opposition because of the relative movements of Earth and Mars around the sun. As Mars and Earth orbit the sun, the distance between them varies from about 75 million km at opposition to about 375 million km when the planets are on opposite ends of the sun.

When Mars is viewed through a telescope, it looks like a red and orange disk. People can easily see white ice caps at the north and south poles of Mars. The darker areas of Mars' surface may look greenish to the observer, but this is an optical illusion caused by the contrast in color between the dark patches and brighter areas. Scientists believe that the darker areas are regions of unweathered bare rock, while the bright areas are regions with deposits of weathered material, especially fine dust.

Scientists believe that Mars' interior consists of a crust, mantel, and core like Earth's interior, but they do not know the relative sizes of these Because no spacecraft has ever brought instruments that can study Mars' interior, the only real information that scientists have are its mass, size, and the structure of the grovity field. From the data scientists can learn some things about density in different parts of the planet.

Mars does not have plate tectonics, or a crust made up of separate sections that move about and sometimes crash into each other. Because Mars is so much smaller than Earth, it cooled quickly after formation and the crust thickened, forming one solid piece and eliminating any possibility of plate tectonics as is seen on the Earth.

Three types of channels on Mars may have been formed by the action of water. These channels may date from a time early in Mars' history when the atmosphere was thicker and liquid water could flow on the surface. Ares Vallis, where the Mars Pathfinder spacecraft was scheduled to land, is one of these outflow channels.

The atmosphere of Mars is 95% carbon dioixde, nearly 3% nitrogen, and nearly 2% argon with tiny amounts of oxygen, carbon monoxide, water vapor, and other gases. The Earth's atomosphere is mostly nitrogen and oxygen. The pressure of Mars' atmosphere ranges from 6 to 10 millibars.

Most scientists today believe that there is no life on Mars. Conditions there are hostile as we know it. Because of the thin atmosphere, harmful radiation can destroy living matter. It is so cold that liquid water cannot exist on the surface during the night. However, it is not impossible that some from of life could exist on Mars today.

This page was written by MELISSA N. ARNOUX in the Astronomy Class of BCC/Broward County. July 1998