The European Space Agency says it has begun training a new group of astronauts for the International Space Station -- by sending them deep underground.

Six astronauts from all over the world will descend into caves on the Italian island of Sardinia and work together to overcome the difficulties of working in a new environment performing a full scientific program with limited supplies, the ESA reported from its Paris headquarters Friday.

Astronauts from the United States, Canada, Russia, Japan and Europe will take part in a five-day above-ground preparation learning to explore dark uncharted areas, safely scale cave walls and move in three dimensions, then they will descend into the caves to a base camp, spending six days exploring and running experiments in complete darkness with only their helmet lamps for illumination, the agency said.

Living and working with isolation and loneliness are factors involved in space missions, and the astronauts underground will learn teamwork as a key to successful missions, it said.

The course aims to improve leadership, teamwork, decision-making and problem-solving skills in a multicultural environment, ESA officials said.

Those skills are needed underground, they said, since in an emergency astronauts in space could return to Earth faster than the so-called cavenauts can ascend to the surface.