The millimeter-scale circles and irregular gray particles in this sample are formerly molten droplets ejected into space when a asteroid hit the Earth 2.63 billion years ago late in the Archean period. Credit: Bruce Simonson, Oberlin College and Conservatory. The sample was cut and polished in Bruce's lab in Ohio, where the photo was taken, but the sample itself came from a spherule bed in Australia. Copyright released with permission for public distribution.