Tl;dr maybe an asteroid was passing nearby, got wrecked, all the little bits turned into a ring a la Saturn, during the Ordovician (right after Cambrian), then the bits slowly fell to earth.
Tl;dr maybe an asteroid was passing nearby, got wrecked, all the little bits turned into a ring a la Saturn, during the Ordovician (right after Cambrian), then the bits slowly fell to earth.