In the Matese mountains of the Italian Apennines, four explorers are preparing to descend into total darkness. For four days, they will live and work together in a pitch-black cave, cut off from the outside world.

Their mission: to explore the unknown, document their findings, and return safely.

During their expedition, the team of ‘cavenauts’ will discover a new world, face challenging situations, and discover new things about themselves and each other. 

ESA’s CAVES training programme offers space explorers the unique opportunity to experience the psychological extremes of real exploration as a multinational crew to better prepare them for the challenges of spaceflight.

Participants in the seventh CAVES edition are ESA astronaut Marco Sieber, NASA’s Jasmin “Jaws” Moghbeli, Makoto Suwa from Japan’s space agency JAXA and Mohammad Al Mulla from MBRSC, the Emirati space agency.

The caves 2025 crew during cave familiarisation training. From left to right, Marco Sieber (ESA), Jasmin Moghbeli (NASA), Mohammad AlMulla (MBRSC) and Makoto Suwa (JAXA). Credits: ESA/V. Crobu

Why caves for space?

The cave environment imposes isolation, confinement, technical challenges and limited supplies – just like in space.

NASA’s Jasmin Moghbeli, who spent 199 days on the International Space Station as Crew-7 commander, is finding many analogies to space conditions throughout the training. “Here, like on the Space Station, you have to constantly focus on where every piece of equipment is, keep situational awareness at all times, communicate effectively with the ground and carefully manage your supplies,” explains Jasmin. 

After putting on their caving equipment, astronauts Jasmin Moghbeli (NASA) and Makoto Suwa (JAXA) perform the buddy check, a safety procedure where explorers inspect each other’s gear and confirm it’s in good working order. ESA / V. Crobu

A spacewalker herself, the training highlights “how important it is to handle your tethers and equipment carefully, and to stay securely attached when climbing or descending walls inside the cave. If you don’t do it right, the risk is real.”

The crew must carry all their gear and food in rucksacks, and navigate sloping, uneven terrain with only the narrow field of view provided by their headlamps.

Preparing for the underworld

Before entering the cave, the crew received a mix of technical lectures, outdoor training and lessons on how to perform effectively as a team to prepare them for the challenges ahead. 

The astronauts learnt about cave mapping, how to perform scientific experiments and the best ways to communicate with each other. They also develop rope climbing skills to move through the cave.

“We trained the crew to be very autonomous in preparing their own expedition, taking care of adjusting their daily plans, packing their equipment, organizing its transport into the cave and deciding on the setup of the campsite. Despite hardly knowing each other before, they quickly bonded and became a very cohesive team,” explains Loredana Bessone, CAVES course director.  

The crew works together to pack and choose their food rations. Credits: ESA/V. Crobu

“I am really curious to explore the unknown and discover new parts of the cave,” says ESA astronaut Marco Sieber. 

The team must organise into roles and elect two commanders. “We are two pilots, a medical doctor and a climate scientist in the team. I want to put my leadership skills to the test with these extraordinary people,” says starting CAVES commander Mohammad Al Mulla. 

Initially, Makoto is campsite manager, while Marco and Jasmin are the survey and communications team in charge of mapping the cave, choosing the best path and reporting their progress to the ground. All roles are swapped halfway through the expedition. “We all lead in a way or another,” adds Mohammad. 

ESA astronaut Marco Sieber prepares the ropes before descending a rock cliff in La Cundra area. Credits: ESA/V. Crobu

Into the deep

CAVES became reality on 24 September as the astronauts descended underground.

Above ground, mission control tracks their progress with a 3D map generated with inputs from the crew as they explore the cave. Scientists can locate the astronauts’ observations paired with pictures, and send their comments back to the cave. 

Just as Hansel left a trail of breadcrumbs to be able to come back home, the crew can leave virtual markers and retrieve them on the Electric Field Book app to understand where they are and pinpoint science locations.

NASA astronaut Jasmin Moghbeli places the communication cable that connects to the phone line along the walls of the cave. Credits: ESA/V. Crobu

The crew can establish contact with the teams outside the cave twice a day using a rudimentary phone line cabled by themselves.  

Just like astronauts, ‘cavenauts’ travel light. They explore the cave wearing a helmet, a harness, two headlamps and carry supplies and various instruments and scientific tools. Their diet mainly consists of dried and tinned foods. A toothbrush and baking soda are part of the basic hygiene kits. 

At base camp the team is left to set up the tents and organise themselves. From that moment, the campsite becomes their ‘home’ for four dark days.

ESA astronaut Marco Sieber takes photographs of the cave to document the environment. Credits: ESA/V. Crobu

The team’s elected commander must organise the group and plan for logistics needs. “We are two pilots, a medical doctor and a climate scientist in the team. I want to put my leadership skills to the test with these extraordinary people,” says CAVES commander Mohammad Al Mulla. 

Makoto is campsite manager, while Marco and Jasmin are the survey and communications team in charge of mapping the cave, choosing the best path and reporting their progress to the ground. All roles are swapped halfway through the expedition. “We all lead in a way or another,” adds Mohammad. 

Cave life

The crew will monitor the ever-changing cave environment. They will perform science experiments include taking swabs in the search of microbes, monitoring radon and carbon dioxide levels and observe the flow of water.

The field scientist in Makoto acknowledges the pressure of sampling with scientific accuracy while managing fatigue during the long days of exploration wrapped in darkness. “It’s not an easy environment, so you have to reserve your energy and stay focused,” says Makoto. 

JAXA astronaut Makoto Suwa takes several measurements of the water in the cave and records them in the Electronic FieldBook. Credits: ESA/V. Crobu

Microbiological contamination from the caving activities is also checked. “Like in space exploration, we are reminded that we might reach places where no one else has been before. We have the duty to preserve it and avoid polluting it,” says Marco. 

“The crew responded brilliantly to all the challenges presented during the training phase. They were focused and disciplined, yet also friendly and open with each other and with the support team. Now, as they take the lead in the expedition, they will put theory into practice and quickly discover, both as individuals and as a team, how to perform effectively under difficult circumstances,” says Samuel Payler, CAVES deputy course director.

Follow their cave expedition on this blog, CAVES Flickr gallery and on ESA’s social media platforms.