Scientists at the SETI Institute and Purdue University have discovered that the only way to produce the unusually tilted moon Deimos orbit from Mars is for the Red Planet to have had a ring billions of years ago. While some of our solar system’s most massive planets have giant rings and numerous large moons, Mars only has two tiny, warped moons, Phobos and Deimos. Though small, these moons hide important secrets about their past in their peculiar orbits.
Scientists long believed that asteroids were captured from the two moons on Mars, discovered in 1877. Since their orbits are almost on the same plane as Mars’ equator, however, the moons must have formed simultaneously to Mars. Yet the orbit of the smallest and farest moon, Deimos, is tilted two degrees. “The fact that Deimos’ orbit isn’t exactly in the plane with Mars’ equator wasn’t considered important and no one cared to try to explain it,” says lead author Matija Cuk, a SETI Institute research scientist. “But once we had a brilliant new idea and were looking at it with new eyes, the orbital tilt of Deimos exposed its great mystery.”
These theories can undergo some serious testing in a few years, as the Japanese space agency JAXA plans to send a spacecraft to Phobos in 2024, which would collect samples from the moon’s surface and return them to Earth . Cuk is hopeful that this will give us firm answers about the dark past of the Martian moons: “I do theoretical calculations for a living, and they are good, but having them tested in the real world once in a while is even better” , he explains in a statement.