PUNTARENAS, Costa Rica - Scientists set off from Costa Rica on Sunday to drill a hole deep under the sea and directly extract rocks from record depths that could add to the understanding of climate change.

The rocks dug up from the lower part of the Earth's crust in the coming weeks will be the closest anyone has come to the vast, churning part of the planet called the mantle, which lies between the crust and the core.

On a 140-meter ship that resembles an oil platform, the 30-member scientific team will bring back rocks from 2 kilometers beneath the sea off Costa Rica's Pacific coast.