The Martian moon Phobos has just a short time left in this solar system. In 30 to 50 million years, it will be gone for good. Terry Hurford of NASA Goddard Spaceflight Center presented the results at the American Astronomical Society's 2015 meeting.
The problem lies in the moon's distance from Mars, just 3,700 miles above its surface. This causes Phobos to move closer to Mars by 6.6 feet every year. As it comes closer in, tidal forces between Mars and Phobos will slowly rip apart the smaller, "rubble pile" like object. In fact, Mars appears to be already well on its way to destroying one of its two moons.
The evidence comes from deep grooves in Phobos' surface, which were once thought to have come from a collision with another solar system body. But the location doesn't radiate out from a crater as once thought. Instead, it seems that tidal forces are creating the grooves, with the pull between Phobos and Mars creating stress fractures in its loose surface.
The likely fate of Phobos will involve the moon getting ripped apart by Mars at the Roche limit, the point in an orbit around a body where an orbiting satellite can be shielded from violent tidal forces ripping it apart. It will then create a temporary ring around Mars that will slowly fall into the atmosphere of the planet. While it'll be far after all of us are dead, our descendants (whatever species they may be) will live in a world without a Phobos. Deimos, Mars' other moon, seems safe for now.
All of this also means that someday, humans may land on a solar system body that will later be destroyed, should NASA opt for a Phobos-first mission to Mars.
Source: NASA
