Underground astronauts preparing for space

We usually send them 400 km up, but next week ESA will be sending six astronauts 800 m underground into the rocky caves of Sardinia, Italy. The caving course recreates aspects of a space expedition with an international crew and has become an essential part of ESA's astronaut training. This year's participants are ESA astronaut Pedro Duque, NASA astronauts Jessica Meir and Richard Arnold, Japanese astronaut Aki Hoshide, Chinese astronaut Ye Guangfu and cosmonaut Sergei Korsakov.