A 300-mile-wide crater has been found in the Wilkes Land region of East Antarctica, south of Australia. Based on the satellite measurements of gravity fluctuations that led to its discovery, the crater is thought to be around 250 million years old, coinciding with the biggest mass extinction in Earth's history. The Permian-Triassic extinction wiped out 90 percent of life on Earth. Scientists believed a meteor impact could have caused such devastation, but an impact crater of the right age and size had not yet been found. According to the discovery team, the Wilkes Land crater is a good candidate: the meteor that caused it would have been up to 30 miles in diameter--four or five times as big as the Chicxulub meteor thought to have killed the dinosaurs 65 million years ago. Above, a combination of radar and satellite imagery highlights the rim of the crater in red and blue. The team presented its preliminary results at the recent American Geophysical Union Joint Assembly meeting in Baltimore.