Mars has two natural satellites, which are its two moons named Phobos and Deimos. The two moons of Mars orbit its atmosphere, just as Earth's moon orbits this planet. The discovery of the two Mars satellites dates back to the late 1800s, owing thanks to astronomer Asaph Hall, who observed the two moons through a telescope at the United States Naval Observatory in Washington, D.C.
The moons of Mars derive their names from horses of Ares, the ancient Greek god of war. The name Phobos translates to "fear," while Deimos translates to "panic." Despite classifying as moons, Deimos and Phobos contain surfaces and cores bearing many of the same materials as asteroids. Some astronomers believe the two satellites actually classify as asteroids, and became trapped in Mars's outer asteroid belt. Both Deimos and Phobos classify as minor satellites, having a small size in comparison to Mars. They have irregular shapes and surfaces covered with craters, appearing more like rocks circling Mars than full, rounded moons. Both satellites circle Mars at rapid rates; Phobos, the larger moon, follows an orbital path closer to Mars's surface. It completes an orbit around Mars in just seven hours, making three full orbits each day. Deimos exists farther from Mars and follows a longer orbital path, completing an orbit in 30 hours.