Enhanced-color image of Phobos from the Mars Reconnaissance Orbiter with Stickney crater on the right. Image source: [1]
Phobos is a moon from Mars and gets its name from one of Mars's helpers, the Roman god of war. Phobos is a dark body that appears to be surface composite by type C materials. It is similar to the type C asteroids that exist in the outer asteroid belt. Some scientists speculate that Phobos, and Mars' other moon, Deimos, are captured asteroids. However, other scientists point to evidence that contradicts this theory. Phobos presents striated spots that are probably fractures caused by the impacts that gave rise to the great craters of this moon.
Orbiting just 6,000 kilometers above the surface of Mars, Phobos is closer to its planet than any other moon in the solar system. The gravity of Mars is attracting Phobos, two meters every hundred years. Scientists expect the moon to crack within 30 to 50 million years.
Phobos always presents the same face to Mars, due to the tidal forces that the planet exerts on its satellite. In general terms, Phobos is a rocky block of irregular shape, about 27 km long on its longest axis. It has an orbital period of 7 hours and 39 minutes. Its surface has a large crater, which has been called Stickney.
Stickney crater, which measures 10 km in diameter, the surface of Phobos is plagued by shallow furrows, which have a width between 100 and 200 meters, and a depth of 20 or 30 meters. The small moats with raised edges, aligned in parallel formations, could be points in which the gas escaped of the underground ice through fissures.
More details here: Phobos
The impact crater Stickney imaged by the Mars Reconnaissance Orbiter in March 2008. Image source: [2]