A kilometer-size asteroid slammed into Earth about 800,000 years ago with so much force that it scattered debris across a 10th of our planet's surface. Yet its impact crater remains undiscovered. Now, glassy remains believed to have come from the strike suggest the asteroid hit southeast Asia as our close ancestors walked the Earth... Aaron Cavosie, an astrobiologist and geochemist at Curtin University in Perth, Australia, and his colleagues examined the chemical composition of three tektites from Thailand. They searched for evidence of reidite, a rare mineral formed only by extreme pressures and temperatures, like those of an asteroid impact....