Most planets that orbit a parent star will also have one or more moons that in turn orbit the world in question itself. Mars, the fourth plant from the sun in this solar system, happens to have two such moons. They are named Phobos and Deimos.
These names stem from Greek mythology. Deimos was said to be one of the sons of the god Ares (Mars) and the goddess Venus (Aphrodite). Phobos, the character for which Mars’ other moon is named, was Deimos’ brother. In the Greek language, Phobos means fear while Deimos means panic.
An American astronomer named Asaph Hall is credited with discovering these two moons of Mars back in 1877. Unlike conventional moons that hold more or less a spherical shape, Deimos in particular resembles a deformed potato! At all of 12.6 kilometers (about 7.8 miles) in diameter, Deimos is also one of the smallest known moons in this solar system. Needless to say, discovering such an object with the available telescopes of 1877 must have proved to be quite a feat.
Deimos is the outermost moon of Mars with a mean orbit of some 23, 459 km (14,571 miles). Both Deimos and Phobos contain carbon-rich rocks, ice and lots of craters. Deimos orbits Mars every 30 hours.
How these two objects became moons of Mars is the subject of debate, but considering that the surface material of these moons is made up of the same compounds as asteroids, it is believed that both Deimos and Phobos were originally a part of the Asteroid belt. Astronomers have theorized that both original orbits of these objects around the sun were affected by Jupiter’s gravitational pull and eventually captured by Mars’ gravity.
The surface of Deimos is smoother than that of Phobos. Lots of craters suggest that the surface was once bombarded with meteorites. When a meteorite strikes a body’s surface, it usually results in ejected debris that falls back to the surface and surrounds the newly-formed crater. However, this debris is absent around the craters on Deimos. This was likely caused by the moon’s low gravity, which allowed the ejected surface material to escape into space. However, some of this material appears to have been moved downward on slopes. In addition, regolith, a collection of dust, loose rock, and other pulverized, transported material can be found on the surface. In places, it is believed to be as thick as 100 meters in depth.
Viking I, an unmanned spacecraft launched in the mid-1970s to land and gather data on Mars, also took pictures of Deimos and Phobos. Sadly, due to budget cuts in space exploration, plans for any future manned missions to Mars and/or its unusual moons remains anyone’s guess.