One summer night in 1877, American astronomer Asaph Hall was looking through his telescope in Washington, D.C. Mars was at ...

Mars may have had a single moon before something smashed into it, tearing it asunder into the two moons we see today. In a study published Monday in Nature, scientists explained how they used the ...

Mars' two moons, Phobos and Deimos, are small, irregular, but orbit in the same equatorial plane as the red planet. Although they've long been thought to be captured asteroids, those orbits would ...

These six images from NASA's Mars rover Curiosity show the two moons of Mars moments before (left three) and after (right three) the larger moon, Phobos, occulted Deimos on Aug. 1, 2013.

Mars' moons are not easy to explain. Both are small — Phobos is 16 miles (26km) across at its widest point, Deimos is just 10 miles (16km) — and lumpy, which makes them look like captured ...

Our Solar System's two innermost rocky planets have no moons. Earth has an unusually large one, the product of a massive collision. And Mars' two moons, Phobos and Deimos, are... well, weird ...

Mars has two small, funky-looking moons with strange orbits, and they may suggest that the red planet once had rings, like some of the larger planets in our solar system. The two lumpy moons ...

These days, our neighbor Mars has just two moons: Phobos and Deimos. But according to a study published Monday in the journal Nature Geoscience, these little satellites may actually be the planet ...

Of Mars’s two moons, Phobos is slightly larger. Both are irregularly shaped, like potatoes. Phobos is about 27 km across on its longest side, and Deimos is 15 km across.

Mars' moons are not easy to explain. Both are small — Phobos is 16 miles (26km) across at its widest point, Deimos is just 10 miles (16km) — and lumpy, which makes them look like captured ...

Another hypothesis is that Phobos and Deimos formed very much like Earth's moon did — that an impact on the surface of Mars threw debris into orbit that eventually coalesced into the two moons ...