The Virgin Galactic SpaceShipTwo, or VSS Enterprise, glides toward Earth on its first test flight after release from the mothership, WhiteKnightTwo, also known as VMS Eve, over the Mojave, Calif., area in 2010. SpaceShipTwo is undergoing rigorous testing before it can carry tourists to space.
PHOTO: Clay Observatory for Virgina Galactic, Mark Greenberg/AP/File
