Seeing the light: Astronauts "cave crew" returns to Earth

Space may be the final frontier but the road to the future sometimes requires astronauts to take very terrestrial detours.

For instance, an international team participating in a European Space Agency training program recently spent six days in a dark cave on the island of Sardinia to simulate real exploration conditions. Why Sardinia? According to ESA, the island is chockablock with "isolated mountains and forest areas, rugged and savage."

For six days they lived and worked in the island's complex cave systems - some of them unmapped or unexplored. "Even for astronauts, life in the dark, cool, humid underground environment can be a completely new situation with interesting psychological and logistical problems," according to Loredana Bessone, an astronaut trainer at the European Astronaut Centre in Cologne, Germany.

The caving team after return to the surface September 21: (clockwise from left) Randolph Bresnik from NASA, Sergey Ryzhikov from Russia, ESA astronauts Thomas Pesquet and Tim Peake, and Norishige Kanai from Japan in front.

The astronauts spent six days living and working in the island's network of cave systems. The idea is that the experience would duplicate the environment they will encounter in space where isolation, confinement, and minimal privacy is the norm. In this image, a view of the valley of the CAVES course during the 'dry run' preparations.

Thomas Pesquet on the second day of exploration during the CAVES 2011 course.

ESA's Thomas Pesquet recalled the most exciting moments as the times "when we were in unknown passages and had to make decisions on how to proceed and how to organize ourselves. We encountered underground lakes, had to decide if we used ropes or an inflatable boat...should we continue together or divide into small groups...and so on."

Here's a shot of a cave during the preparatory training of the CAVES 2011.

The scientific work schedule included mapping, photography, monitoring air flow, temperature and humidity, and taking geological and microbiological samples.