NASA's Vault

"Inside the vault: A rare glimpse of NASA's otherworldly treasures":

Among the samples on display is the so-called “Genesis rock,” which appears to have been coated by powdered sugar. The crew of Apollo 15 had been tasked with searching for just such an anorthosite rock, and they found it near the Apennine Mountains. Dating to 4.1 billion years old, within a few hundred million years of the Solar System’s formation, the Genesis rock helped validate the theory that the Moon formed after a Mars-sized object collided with Earth in the very early Solar System.