Billion-dollar drilling project aims for Earth's mantle

A Japanese-led project aims to drill to the Earth's mantle, a 3,000 kilometre-thick layer of slowly deforming rock between the crust and the core. In its early stages, the $US1 billion mission would deploy a drill just 30 centimetres wide to bore into the Earth's crust to bring back the first ever samples of fresh mantle rock. Jim Drury reports.