Earth may have had a ring
Impact craters from this period cluster suspiciously near the equator — as if debris rained from a ring.
- When
- Known to
- ± 3 million years
- Era
- Ordovician, Paleozoic
Twenty-one Ordovician impact craters all sit within thirty degrees of the equator, despite most of the suitable land at the time lying elsewhere. A 2024 study proposes that an asteroid passing within Earth's Roche limit was torn apart into a debris ring, which then decayed onto the equator over millions of years. The ring's shadow could also have cooled the planet, offering a mechanism for the icehouse that follows. It is a striking hypothesis rather than an established fact.