The small inner planets may have had rings in the past and may have rings again in the future. One prevalent theory says that ring systems are much younger than the age of the Solar System, and as such, may come and go with time. If Earth had rings in the past — for example, from the breakup of a comet or asteroid that came too close — then those rings may have spread out and disappeared long ago. Earth might have a ring in the future if a comet or asteroid passes Earth in just the right orientation to be broken apart by Earth’s gravity rather than disintegrating in Earth’s atmosphere. Our Moon is too distant to provide material for a future Earth ring; however, the Moon may have formed from a huge, very short-lived ring of material encircling Earth. Such a ring would have been formed if a huge body — the size of Mars or larger — hit Earth, spewing huge amounts of debris into orbit around our planet. In a very short time, this debris would gather together to form the Moon.