Phobos (moon)

Phobos colour 2008

Phobos is one of the two moons of Mars, alongside its smaller counterpart, Deimos. It is the larger and closer of the two, making it a significant subject of study in astronomy and planetary science. Phobos orbits closer to Mars than any other moon in the Solar System orbits its planet, which leads to unique characteristics and phenomena.

Discovery and Naming

Phobos was discovered on August 18, 1877, by Asaph Hall, an American astronomer. The discovery was made at the United States Naval Observatory in Washington, D.C., using the 26-inch refractor telescope. Hall also discovered Deimos a few days later. The name "Phobos" is derived from Greek mythology, representing fear and panic, and is a fitting companion to "Deimos," which symbolizes terror and dread. Both names were suggested by Henry Madan, based on their association with the god Mars in ancient mythology.

Physical Characteristics

Phobos is an irregularly shaped object with dimensions of approximately 27 × 22 × 18 kilometers. Its surface is covered with craters and grooves, a testament to its history of impacts. The most prominent feature on Phobos is the Stickney crater, a large impact crater that measures about 9 kilometers in diameter. The surface of Phobos also exhibits a network of grooves and streaks, which are believed to be caused by structural failure from the impact that created Stickney.

The moon's composition is thought to be similar to that of C-type asteroids, with a mixture of rock and ice. However, its density is too low to be entirely made of rock, suggesting significant porosity or a composition of lightweight materials.

Orbit and Rotation

Phobos orbits Mars at a distance of only about 6,000 kilometers from the planet's surface, closer than any other known planetary moon. It completes an orbit around Mars in approximately 7.6 hours, which is faster than Mars rotates on its axis. This means that Phobos rises in the west and sets in the east on Mars, unlike most other moons in the Solar System.

Due to tidal forces, Phobos is gradually spiraling inward towards Mars. It is estimated that it will either crash into Mars or break up into a ring system in 30 to 50 million years.

Exploration

Phobos has been the subject of several space missions, primarily flybys conducted by missions to Mars. The Soviet Union's Phobos program in the late 1980s was the first dedicated effort to study Phobos, though it ended in failure. More recently, missions like Mars Express and Mars Reconnaissance Orbiter have provided detailed images and data on Phobos. There are also proposals for future missions specifically aimed at exploring Phobos, including sample return missions.

Significance

The study of Phobos is significant for several reasons. Understanding its composition and structure can provide insights into the early Solar System and the processes that formed the moons of Mars. Additionally, Phobos could serve as a base or waypoint for human exploration of Mars, due to its low gravity and proximity to the planet.

See Also

• Deimos
• Mars
• Astronomy
• Planetary science