Today it was announced that Phobos was formed in a giant explosion, similar to how the Moon was formed. Phobos is actually coming closer to Mars every year, and has an expected 10 million year lifetime. It seems highly unlikely that Phobos could have been formed billions of years ago, and yet we first see it just a few million years before it's death.
My question is, is this even possible? Namely, if an object orbits just inside the geostationary belt of said object, which is the point at which it will come either closer or further away, could it survive in orbit for billions of years?