Mars, the fourth planet from the Sun, has two small moons named Phobos and Deimos. Unlike Earth’s moon, which is relatively large and spherical, the Martian moons are tiny and irregularly shaped, resembling asteroids more than typical moons.
Phobos
Characteristics:
- Size: Phobos is the larger of the two moons, with a mean radius of about 11 kilometers.
- Orbital distance: it orbits Mars at a distance of approximately 6,000 kilometers from the planet’s center, making it one of the closest moons to its planet in the solar system.
- Orbital period: Phobos orbits Mars very quickly, completing one orbit in just about 7 hours and 39 minutes.
- Surface: the surface of Phobos is heavily cratered and covered with a layer of dust and loose rocks. The most prominent feature is the large crater named Stickney, which measures about 9 kilometers in diameter.
Phobos is thought to be a captured asteroid, possibly a carbonaceous chondrite, which is a type of stony meteorite that contains organic compounds.
Phobos is gradually spiraling inward towards Mars due to tidal forces. It is expected to either crash into Mars or break apart and form a ring around the planet in about 30 to 50 million years.
Deimos
Characteristics:
- Size: Deimos is smaller than Phobos, with a mean radius of about 6 kilometers.
- Orbital distance: Deimos orbits Mars at a distance of approximately 20,000 kilometers.
- Orbital period: It takes Deimos about 30.3 hours to complete one orbit around Mars.
- Surface: like Phobos, Deimos is heavily cratered, but it has a smoother appearance due to a thick layer of regolith, which is loose, fragmented material covering solid rock.
Similar to Phobos, Deimos is also believed to be a captured asteroid. Its composition is thought to be similar to that of D-type asteroids, which are dark and carbon-rich.
Deimos is slowly drifting away from Mars at a rate of a few centimeters per year. Over a very long period, this could result in Deimos escaping Mars’ gravity altogether.
Exploration and scientific importance
Both moons of Mars have been the subject of numerous scientific studies and space missions due to their unique characteristics and the insights they can provide into the history of the solar system. The Soviet Union’s Phobos program in the late 1980s aimed to explore Phobos, although the missions were only partially successful. More recently, there are plans for future missions, including sample-return missions, to further study these intriguing Martian moons.
Phobos and Deimos continue to captivate scientists and astronomers, not only for what they can tell us about Mars and its history but also for their potential role in future manned missions to the Red Planet. Their low gravity and proximity to Mars make them interesting candidates for exploration bases or stepping stones for human missions to Mars.
