New research shows that when an asteroid slammed into the moon billions of years ago, it carved out a pair of grand canyons on the lunar far side. That's good news for scientists and NASA, which is looking to land astronauts at the south pole on

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.