Could We Live in Caves on the Moon? Inside the Search for Lunar Lava-Tube Habitats

The question of whether humans could shelter inside the Moon's underground caves has moved from science-fiction speculation to an active NASA research program. On September 30, 2026, according to Astronomy.com, NASA selected a mission called GIMLI to investigate a specific hole in the lunar surface, the Marius Hills Pit, to determine whether it is the doorway to a vast hidden cavern.

Why this is in the news now

NASA has chosen a proposal led by the Planetary Science Institute (PSI) in Tucson, Arizona, called GIMLI — Geophysical Instruments for Marius Lunar pit Investigation — to probe the Marius Hills Pit in the Oceanus Procellarum region, according to PSI's own announcement. The principal investigator is Nathaniel 'Than' Putzig, with Gareth Morgan as deputy principal investigator.

PSI is partnering with Honeybee Robotics, a Blue Origin company, to build the instruments, while the Norwegian Space Agency will supply ground-penetrating radar. The payload will travel to the Moon through NASA's Commercial Lunar Payload Services (CLPS) program, funded under NASA's PRISM initiative (Payloads and Research Investigations on the Surface of the Moon), PSI said. No launch date has been confirmed yet.

According to PSI's announcement, the underground caves GIMLI will study 'may one day provide a safe haven for astronauts to escape the radiation and extreme temperature swings present at the lunar surface.' PSI's own text presents this as a description of the caves' potential rather than as Putzig's personal words.

What exactly is a lunar lava tube?

Billions of years ago, flowing lava on the Moon formed long underground channels. When the molten rock drained away or the surface crust cooled and collapsed, it sometimes left open tunnels — lava tubes — with occasional holes, or 'pits,' where the roof caved in, according to coverage from Astronomy magazine and Chile's BioBioChile. Japan's Kaguya (SELENE) orbiter photographed the Marius Hills Pit — in 2008 according to Astronomy.com, or 2009 according to BioBioChile — and the pit measures roughly 65 by 90 meters (213 by 295 feet) across, per PSI and Astronomy.com reporting.

A separate, already-confirmed example is the Mare Tranquillitatis pit, about 400 kilometers (250 miles) from the Apollo 11 landing site. Radar data from NASA's Lunar Reconnaissance Orbiter, analyzed by University of Trento researchers Leonardo Carrer and Lorenzo Bruzzone and published on June 15, 2024, showed the pit connects to an underground cave extending at least 40 meters wide, according to Wikipedia's summary of that study. The pit itself has an outer funnel 140–146 meters wide and an inner shaft about 88–100 meters across and roughly 105 meters deep.

Why a cave could be a better home than the open surface

The lunar surface has no atmosphere and almost no magnetic field, so it is bombarded by galactic cosmic rays, occasional solar particle storms, and micrometeorites, and it swings between extreme heat and extreme cold over each roughly month-long day-night cycle. A 2020 study published in the Journal of Radiological Protection quantified how much a lava tube would cut radiation exposure compared with the open surface.

A single solar energetic particle event, such as the one recorded in July 2000, could deliver about 2,190 millisieverts to an unshielded person on the surface, the same study found — a dose that underground rock would largely block. Separately, thermal modeling of the Mare Tranquillitatis pit cited on Wikipedia found that permanently shadowed sections of the cave stay near a stable 290 K (about 17°C). The same modeling found the pit itself ran about 100 K warmer than the surrounding surface at night and about 20 K cooler during the day — a narrower temperature range than the open lunar surface experiences, according to Wikipedia's summary of the study.

How scientists plan to confirm a hidden cave

GIMLI will not simply look into the pit — it will try to map what lies beneath and beside it. According to PSI and reporting by Astronomy magazine, the instrument package includes ground-penetrating radar, an active-source seismic system (described as the first intentional active-source seismic survey on the Moon since the Apollo missions), a gravimeter to detect low-density voids, and cameras to photograph the pit walls and surrounding terrain.

The team, which also includes researchers from Boise State University, Johns Hopkins University, the Lunar and Planetary Institute, and the University of Oslo, will use the combined data to estimate whether — and how far — a lava tube extends from the pit, and to study the exposed rock layers in the pit walls for clues about the Moon's volcanic past.

What remains unknown

No lunar cave has yet been explored by a robot or human, and GIMLI's own launch date and lander have not been finalized. Scientists do not yet know the exact size, stability, or accessibility of any cavity beneath the Marius Hills Pit, and even the confirmed Mare Tranquillitatis cave has only been mapped by orbital radar, not visited directly. Turning a lava tube into a livable habitat would still require engineering for air, pressure, lighting, and sealing entrances — steps not yet addressed by current missions, based on the available reporting.

Key points

• NASA selected the PSI-led GIMLI mission on September 30, 2026, according to Astronomy.com, to investigate the Marius Hills Pit, a 65-by-90-meter hole photographed by Japan's Kaguya orbiter in 2008 (Astronomy.com) or 2009 (BioBioChile).
• A 2024 study using NASA Lunar Reconnaissance Orbiter radar data confirmed a separate lava-tube cave beneath the Mare Tranquillitatis pit, near the Apollo 11 landing site.
• A 2020 radiation study estimated that a horizontal lava tube could cut annual cosmic-ray exposure from over 400 mSv on the surface to under 1 mSv.
• GIMLI will use radar, seismic sensors, a gravimeter and cameras, delivered via NASA's Commercial Lunar Payload Services program; no launch date is set yet.