Researchers Say They’ve Solved the Puzzling Mystery of the Moons of Mars

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Researchers Say They've Solved the Puzzling Mystery of the Moons of Mars:

Mars's two moons, Phobos and Deimos, have puzzled researchers since their discovery in 1877. They are very small: Phobos's diameter of 22 kilometers is 160 times smaller than that of our Moon, and Deimos is even smaller, with a diameter of only 12 kilometers. "Our moon is essentially spherical, while the moons of Mars are very irregularly shaped - like potatoes," says Amirhossein Bagheri, a doctoral student at the Institute of Geophysics at ETH Zurich, adding: "Phobos and Deimos look more like asteroids than natural moons."

This led people to suspect that they might in fact be asteroids that were captured in Mars's gravity field. "But that's where the problems started," Bagheri says. Captured objects would be expected to follow an eccentric orbit around the planet, and that orbit would be at a random inclination. In contradiction to this hypothesis, the orbits of the Martian moons are almost circular and move in the equatorial plane of Mars. So, what is the explanation for the current orbits of Phobos and Deimos? To solve this dynamic problem, the researchers relied on computer simulations.

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