Tycho is a crater on the moon that has a little "island" peak in its center. If you're feeling immature, it looks a bit like a breast. With that analogy in mind, what you're looking at here is a close-up of the nipple—the very tip-top of Tycho's central peak. The photo was taken by NASA's Lunar Reconnaissance Orbiter.
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.