Mars has been on a lot of people’s minds lately, with the Curiosity rover and other exploratory vehicles finding all kinds of cool things on the Red Planet. But two scientists at the University of California Berkeley, have some mixed news for the planet: it’s going to lose one of its moons, Phobos, but it will gain a ring, like Saturn.
That’s because Phobos, which is much, much smaller than our own moon, is slowly falling towards the planet, a few centimeters a year. Eventually, as it gets closer to the planet, gravitational forces will tear it apart, because Phobos is already porous and fractured. It will effectively shatter and the parts will spread out in the orbit of the plant, forming a ring, just like Saturn, Jupiter, Uranus, and Neptune all sport.
When is this going to happen? Not soon, at least for humans. The destruction of Phobos is expected to happen sometime in the next 20 to 40 million years, so none of us will see it. Over time, between 1 and 100 million years, all those old moon chunks will fall out of the sky, leaving just Deimos, Mars’ other moon, in orbit around it.
The researchers who figured this out, Benjamin Black and Tushar Mittal, were interested in studying how moons interacted with planets when the solar system was young. One of the going hypotheses for how the largest planets in our solar system got their rings is that they once had more moons which were torn apart. Only one other moon in the solar system, Neptune’s largest moon Triton, is falling towards it’s planet. Ours is actually moving away from us.
This new information could help us better understand the formation of planets, about 20-30% of which are estimated to acquire moons early on, which subsequently fall to their doom on the planet’s surface, or circling it like a ring.