One summer night in 1877, American astronomer Asaph Hall was looking through his telescope in Washington, D.C. Mars was at its closest point to Earth in its orbit, and Hall had one question on his ...

Mars, the fourth planet from the Sun, is a subject of fascination for astronomers. Though significantly smaller than Earth, ...

See stunning photos of Phobos and Deimos, the small moons of Mars, as seen by spacecraft on and orbiting the Red Planet. Phobos is the largest moon of Mars, with Deimos as a smaller satellite.

Billions of years ago, Mars suffered from numerous big impacts, and the resulting backwash ultimately scarred the surface of Phobos, one of the Red Planet's two tiny moons, researchers say.

Mars' largest moon, Phobos, is slowly falling toward the planet, but rather than smash into the surface, it likely will be shredded and the pieces strewn about the planet in a ring like the rings ...

Phobos is very close to its planet Mars, but the intimacy of that relationship also means destruction for the moon, NASA says this week.

Mars’ closest moon moves closer to Mars by about six feet every hundred years, and as Phobos gets closer to the planet’s surface, the gravitational pull increases. Soon these stresses will be ...

Mars actually has two moons: Phobos and Deimos. They might more properly be called satellites, however, because they are extremely small, only a few kilometers in diameter.

Previously unpublished photos of Mars' moon Phobos hint that the mysterious satellite may actually be a trapped comet — or perhaps just a piece of one, along with its twin moon Deimos.

A new study has revealed that the weird parallel grooves on the surface of Mars' largest moon Phobos could be a sign that the Red Planet's gravity is ripping the satellite apart.

Phobos, a tiny moon with a potato-like shape, has puzzled researchers for decades, and now some of those answers might be coming to the surface.