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  3. Mars
  4. Moons

Moons of Mars

Mars has 2 known natural satellites.

About Mars's Moon System

Mars has two small, irregularly shaped moons: Phobos and Deimos. Both were discovered in 1877 by the American astronomer Asaph Hall. Phobos, the larger of the two at roughly 22 km across, orbits extremely close to Mars at just 6,000 km above the surface -- closer than any other known moon to its parent planet. It completes an orbit in only 7 hours and 39 minutes, rising in the west and setting in the east twice per Martian day. Deimos, with a mean radius of about 6 km, orbits much farther out at 23,460 km. Both moons are thought to be captured asteroids, though their near-circular, equatorial orbits have led some scientists to propose they may have formed from debris created by a large impact on Mars.

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