NASA Selects GIMLI Mission to Probe Lunar Cave as Potential Artemis Base Site

NASA has chosen a mission to answer a question that has lingered since astronauts last walked the Moon fifty years ago: what lies beneath the surface? The Geophysical Instruments for Marius Lunar pit Investigation, or GIMLI, will descend to the Moon's Marius Hill region to probe a hole in the ground—a skylight, as scientists call it—and determine whether a vast underground cave system extends beyond what orbital cameras can see.

The mission sits at the intersection of two urgent needs. NASA's Artemis program aims to establish sustained human presence on the Moon, not brief visits but long-duration operations that require infrastructure, habitats, and protection from the harsh surface environment. Simultaneously, space agencies recognize that caves and lava tubes could provide exactly that: natural shelters from radiation and temperature extremes, places where astronauts might live and work safely. Orbital observations have long suggested these spaces exist—sinuous rilles marking collapsed lava tubes, and pits like Marius Hill that may open into stable chambers formed billions of years ago when the Moon was still volcanically active. But suggestion is not certainty. GIMLI will move from inference to evidence.

The mission is led by Than Putzig, an associate director and senior scientist at the Planetary Science Institute, working alongside the Norwegian Space Agency and Honeybee Robotics, which will build much of the robotic equipment. NASA will provide the lander and rover through its Commercial Lunar Payload Services program, with funding flowing through the Payloads and Research Investigations on the Surface of the Moon initiative. The collaboration reflects how lunar exploration has become a distributed enterprise, drawing expertise and resources from multiple nations and private firms.

What makes GIMLI distinctive is its toolkit. The mission will carry ground-penetrating radar to image subsurface structures, seismic sensors to detect vibrations traveling through rock and regolith, a gravimeter to measure subtle variations in gravitational pull that hint at voids below, and cameras to document the pit walls and surrounding terrain. This combination of methods—particularly the seismic component—marks a return to techniques last employed by Apollo astronauts more than fifty years ago. Putzig has long wanted to revive active-source seismic surveying for planetary science, and GIMLI offers that opportunity. The instruments working together will reveal not just whether a lava tube exists, but its dimensions, composition, and structural integrity.

The Marius Hill Pit sits in Oceanus Procellarum, one of the Moon's most volcanically diverse regions. Even if GIMLI fails to confirm an extended cave system, the data will illuminate how the pit formed and what the surrounding geology reveals about the Moon's volcanic past. The pit walls themselves will expose layers of regolith and lava flows invisible to orbiters or rovers, a stratigraphic record written in stone. And if subsurface spaces are found, their interiors may preserve evidence of the volcanic processes that shaped the Moon itself—a geological archive sealed for billions of years.

Gareth Morgan, a senior scientist at PSI and deputy principal investigator for GIMLI, frames the stakes plainly: confirming a substantial lava tube would reshape understanding of how volcanism operated on the Moon. Lava tubes are common features of basaltic volcanism on Earth; finding them on the Moon means terrestrial knowledge can illuminate lunar history. But the practical implications run deeper. A confirmed, stable lava tube would fundamentally alter how NASA designs habitats and infrastructure for Artemis. Instead of building surface structures that must withstand radiation and temperature swings, engineers could work with natural architecture—caves that already exist, already endure, already shelter.

The mission represents the kind of work the Planetary Science Institute was built to pursue: taking a scientific question studied from orbit and developing a way to investigate it directly on the ground. GIMLI will land, deploy its instruments, gather data, and transmit findings back to Earth. The results will either confirm what orbital observations have suggested or reveal that the Moon's subsurface holds different secrets than expected. Either way, the data will inform the next phase of lunar exploration—one in which humans do not simply visit the Moon, but build there, live there, and use what the Moon itself provides.