Martian Moons

Mars and Earth are the only terrestrial planets with moons. As we have said, the earth’s moon is remarkably large, comparable in size to some of the moons of Jupiter. The moons of Mars, colorfully named Phobos (Fear) and Deimos (Panic), after the horses that drew the chariot of the Roman war god, were not discovered until 1877. They are rather unimpressive as moons go, resembling large asteroids. They are small and irregularly shaped (Phobos is 17.4 miles long 12.4 miles [28 km 20 km] wide, and Deimos is 10 miles 6.2 miles [16 km 10 km]). They are almost certainly asteroids that were gravitationally captured by the planet and fell into orbit around it.