Geophysicists are returning to Earth's most famous cosmic bullseye. Today, from a drill-ship off the coast of Yucatán, Mexico, they will start to penetrate the 200-kilometre-wide Chicxulub crater, which formed 66 million years ago when an enormous asteroid smashed into the planet. The aftermath of the impact obliterated most life on Earth, including the dinosaurs. The expedition is the first to directly probe one of Chicxulub's most striking features — its 'peak ring', a circle of mountains that rises within the crater floor. Scientists have yet to fully explain how peak rings form, even though they are common in big impact craters across the Solar System. At Chicxulub, researchers will look for evidence to explain how a 14-kilometre-wide asteroid could have punched a hole that pushed rocks from the surface down some 20–30 kilometres. Flowing like liquid, the rocks then rebounded towards the sky — reaching as far as 10 kilometres above the original ground level — and finally splattered down to form a peak ring. http://www.nature.com/news/geologists-to-drill-into-heart-of-dinosaur-killing-impact-1.19643
