Follow this truly international team of astronaut explorers deep under the surface during their ESA #CAVES2016 scientific expedition. br br NASA's Jessica Meir and Ricky Arnold, ESA's Pedro Duque, JAXA's Aki Hoshide, Roskosmos's Sergei Korsakov and CNSA's Ye Guangfu. ESA is preparing astronauts from all space agencies to become effective space explorers, taking them in expeditions in one of the last frontiers of exploration on Earth: its subsurface. br br CAVES, ESA's unique training programme for astronauts, takes place over a couple of weeks in Sardinia's Supramonte. Six astronauts spend two weeks deep in caves, in the dark and cold. They are separated from the outside world, doing scientific research and daily tasks together, as a group, just like in space. Moving in the cave system is also comparable to spacewalking with the use of harnesses and safety devices. br br Read more about CAVES (Cooperative Adventure for Valuing and Exercising human behaviour and performance Skills) on our dedicated website () and read more about the CAVES 2016 campaign in the blog ().