Dating craters: Wolfe Creek is younger, Meteor Crater older, than previously thought

How old are impact craters on Earth?

This is a hard question to answer, for a lot of reasons. For one thing, big impacts are rare, so craters don't get made very often. That's a good thing! But it means we don't have lots of examples, so it can be difficult to work with them.

For another, Earth is an active planet. Air, water, tectonics... these are all sources of erosion, and after a few hundred thousand — or hundred million — years, craters fade away. If it weren't for those factors, the sur...