The Satellite Phobos
Phobos [FOH-bohs] (fear) is a moon of Mars and in Greek mythology, Phobos is one of the sons of Ares and Aphrodite. It is the largest moon of Mars and is closer to the planet than Deimos. The moon seems to be comprised of a C-type material (a carbon compound) that is most likely mixed with ice due to its low density. On the surface, Phobos has a layer of dust on the surface, indicating heavy collisions by other small bodies
Phobos was discovered in August 12, 1977 by Hall and closely photographed almost a hundred years later by the Mariner 9 in 1971. It lies a distance of about 6000 km from the surface of Mars and has a diameter of 22.2 km. Its mass in scientific notation is 1.08 x 10^16 kg and is one of the smallest moons in the solar system. Other theories speculate the Phobos was caught into Mars' orbit long ago.
Like many other heavenly bodies, Phobos has a distinguishing feature. A large crater named Stickney lies in one of the moon's sides. This crater seemed to have been the result of a powerful collision that nearly shattered the moon as evidenced by the long streaks running down the sides from the crater. Phobos is also on a collision course with Mars. Since it is orbiting below the synchronous orbit radius, forces will lower the moon closer and closer to Mars (current rate at about 1 meter per century) that in about 50 million years, Phobos will collide into the planet.
Besides the Mariner 9, a series of other spacecraft have also visited Phobos. In 1971, Viking 1 came to close proximity to the moon as well as the soviet Phobos 2 in 1988. To collect data, Phobos carried an on-board video spectrometric system (VSK) designed to observe the surface of the moon by spectral analysis. The system was created by an international cooperation of many scientific and industrial facilities from the USSR, Bulgaria and GDR. During its trip, Phobos 2 had detected outgassing from the surface but before it could determine the source, it disappeared without a trace. The other Phobos probe satellite successfully took pictures with the VSK system in three spectral bands.
Both Phobos and Deimos are suspected to be captured asteroids either from our own asteroid belt or another part of our universe. In the future, scientists plan to use Phobos as a means of studying Mars by mounting space stations on the surface. The main reason behind this is that Phobos orbits Mars twice a day and is extremely close to the planet's surface, making it very easy to see the surface on Mars.