A study funded by the U.S. space agency suggested oxygen existed in Earth's atmosphere much earlier than thought. Two separate teams of astrobiologists found evidence of oxygen in the Earth's oceans and atmosphere approximately 2.5 billion years ago by analyzing a nearly 1-mile-long drill core from Western Australia. "We seem to have captured a piece of time during which the amount of oxygen was actually changing -- caught in the act, as it were," said Arizona State University-Tempe Associate Professor Ariel Anbar, who led one of the research teams. The other research group was led by Alan Kaufman of the...