On Friday, six astronauts will descend 800 meters into the rich subterranean cave system of Sardinia, Italy. They will remain deep underground for six nights, collecting data, performing experiments, and generally adjusting to the reality of life in an otherworldly environment. The expedition, called CAVES (Cooperative Adventure for Valuing and Exercising), aims to prepare astronauts for the physical and mental challenges of spaceflight.
"It really is a psychologically transforming experience," said astrobiologist Penelope J. Boston in a video about the project. "When you explore caves and you are in for many days, your sensory abilities are different. This really is like entering an alien world. It's like going on an expedition to another planet."
Indeed, the 2016 team—which includes Pedro Duque of Spain, Aki Hoshide of Japan, Ye Guangfu of China, Sergei Korsakov of Russia, and Jessica Meir and Richard Arnold of the United States—will have to operate in extremely dark, isolated environments without the circadian cues of day and night.
Scaling cave walls will give them a sense of what it's like to conduct a spacewalk, while communicating across linguistic and cultural barriers provides the groundwork for the kind of cosmopolitan collaboration required aboard the International Space Station (ISS).
"We are very pleased to include the first female astronaut and first 'taikonaut' in this CAVES course, creating an even better mix of cultures and experience to put the astronauts' behaviour to the test," said mission director Loredana Bessone in a statement. ("Taikonaut" is the term for a Chinese astronaut).
In addition to providing a crash course for the daily rigors of off-Earth living, caves are also a valuable resource in the search for extraterrestrial life. The ecosystems within them are notorious for producing evolutionary weirdos, intricately adapted to their unusual surroundings. Astrobiologists can use these organisms as a metric for projecting the habitability of worlds beyond Earth.
What's more, the fact that many caves have been discovered on other planets raises the possibility of interplanetary spelunking. Indeed, if humans were to invest in a long term base on the Moon or Mars, caves might come in handy as a natural protective habitat as well as an obvious place to hunt for alien life.
"The potential exists for future human exploration in these kinds of structures," Boston said. "The rock over a cave is very good at helping to screen out very high energy-ionizing radiation. These natural features, because they already exist in these environments, provide us with an ability to actually modify those for human use with much less payload penalty than if we had to take all that structure and radiation protection with us."
While exploring alien caves sounds like the premise for a space horror flick, it would be useful for humans to gain any edge in any alien environment. In short: Let's all go live in Moon caves.