Lunar Rille
Lunar Rille Rima Sharp on the Moon's near side is a rille—German for the "groove." This particular type of rille, a sinuous rille, is thought to have formed as the result of lava flows or collapsed lava tubes. Many sinuous rilles have crater-like features at their points of origin. NASA/GSFC/Arizona State University

"We're changing the world. Are you in?"
- CEO Bill Nye

Sign up for email updates