From caves to the cosmos | Space photo of the day for Oct. 14, 2025

Many parallels exist between being high above the Earth and deep underground. Both environments are covered in darkness, isolated from the rest of humanity and demand resilience, discipline and trust in one’s team.

In each setting, explorers carry their own light and equipment to places where no one can survive unaided. For astronauts belonging to the European Space Agency, traversing underground caves can be a helpful simulation for the challenges of space exploration.

What is it?

Deep within the Italian Apennines, ESA astronaut Marco Sieber paused in a narrow passageway of a vast cave. For four days, he and an international crew had traded the sky for subterranean darkness as part of the ESA’s CAVES training program.

The simulation demanded constant vigilance. The team traversed steep and uneven ground, overcame vertical drops of up to 60 feet (20 meters) using rope techniques and transformed a small underground site into a temporary base. In this confined home, they prepared food, rested and shared their experiences.

Where is it?

This photo captured a 2 mile (3.5 kilometer) long cave in the Italian Apennine mountains.

Why is it amazing?

Sieber was joined by NASA astronaut Jasmin “Jaws” Moghbeli, JAXA (Japan Aerospace Exploration Agency) participant Makoto Suwa and Mohammad Al Mulla from the Mohammed Bin Rashid Space Center of the United Arab Emirates.

The four team members show just how international astronaut training simulations can be as the few monitored environmental changes, sampled microbial life and tracked radon and carbon dioxide level, mirroring the kind of data collection and monitoring vital to long-duration space missions.

Siber shared his thoughts about the simulation on a recent episode of ESA’s “Astro chat” podcast.

Want to learn more?

You can learn more about astronaut trainings and the European Space Agency.