Phoberus

Phoberus is a moon of the planet Mars. It is the smaller and more distant of the two Martian moons, the other being Deimos. Phoberus is irregularly shaped and orbits Mars in a highly inclined and eccentric orbit.

Discovery and Naming

Phoberus was discovered on August 18, 1877, by American astronomer Asaph Hall at the United States Naval Observatory in Washington, D.C., along with its companion moon, Deimos. Hall named Phoberus after Phobos, one of the sons of Ares (the Greek equivalent of the Roman god Mars) in Greek mythology. Phobos was the god of fear or panic.

Physical Characteristics

Phoberus is a small, dark, and heavily cratered object. It measures approximately 27 × 22 × 18 kilometers in diameter. Its surface is characterized by numerous craters, grooves, and ridges. The largest crater on Phoberus is Stickney Crater, which is approximately 9 kilometers in diameter and occupies a significant portion of the moon's surface. The presence of such a large crater suggests that Phoberus has experienced significant impacts in its history.

Orbit

Phoberus orbits Mars at an average distance of approximately 9,377 kilometers from the planet's center. It completes one orbit around Mars in approximately 7 hours and 39 minutes, which is faster than Mars rotates. This means that, as viewed from the surface of Mars, Phoberus rises in the west and sets in the east. Its orbit is decaying, and it is predicted that Phoberus will eventually either break apart and form a ring around Mars or impact the Martian surface in millions of years.

Composition

The composition of Phoberus is thought to be similar to that of D-type asteroids, which are common in the outer solar system. These asteroids are typically composed of carbonaceous chondrites, which are rich in carbon and organic compounds. The low albedo (reflectivity) of Phoberus supports this hypothesis.

Exploration

Several spacecraft have observed Phoberus from orbit around Mars. These include the Mariner 9, Viking 1 and 2 orbiters, Mars Global Surveyor, Mars Express, and Mars Reconnaissance Orbiter. These missions have provided valuable data about the moon's size, shape, surface features, and orbit. Future missions are planned to study Phoberus in greater detail, potentially including sample return missions to analyze the moon's composition.