The Grand Canyon in Arizona is one of Earth's natural wonders, carved out over millions of years by the gradual erosion power of the Colorado River. Close to the moon's south pole are two canyons each comparable in size to the Grand Canyon that were born in a much different process.

The lunar canyons Vallis Schrödinger and Vallis Planck are extraordinarily deep, and scientists now know the valleys were carved by bullet-fast moon rocks.