NASA's GIMLI Mission Will Hunt for a Hidden Cave Beneath a Moon Pit

There is a hole on the moon roughly the length of a football field across. For years, scientists have studied it from orbit and wondered what lies beneath it. Now NASA has chosen a mission to go and find out.

The mission is called GIMLI, and its target is the Marius Hills Pit, a steep sided opening in one of the moon's most volcanic regions. This piece draws on NASA's announcement, the Planetary Science Institute's release and reporting this month from Astronomy magazine and EarthSky.

What NASA Announced

On September 30, 2026, NASA announced three new science investigations selected through its Payloads and Research Investigations on the Surface of the Moon program, known as PRISM. The payloads will travel to the lunar surface on commercial landers through the agency's CLPS initiative as part of its Moon Base Program.

GIMLI stands for Geophysical Instruments for Marius Lunar pit Investigation. NASA lists Dr. Nathaniel "Than" Putzig of the Planetary Science Institute in Tucson as principal investigator. According to the institute, Honeybee Robotics will build much of the instrumentation and help integrate it onto a lander and rover, while the Norwegian Space Agency will provide the ground penetrating radar.

The team also includes researchers from Boise State University, Johns Hopkins University, the Lunar and Planetary Institute and the University of Oslo. As Astronomy pointed out, the name is a nod to the cave loving dwarf Gimli from The Lord of the Rings. EarthSky reported that no official launch or arrival date has been announced yet.

A Pit in the Ocean of Storms

The Marius Hills Pit sits in Oceanus Procellarum, the Ocean of Storms, a vast dark lava plain on the western side of the moon's near side. Astronomy describes the opening as roughly 65 by 90 meters, or about 213 by 295 feet. EarthSky puts its depth at around 50 meters and notes it is one of nearly 300 such pits found on the moon so far.

On Earth, lava tubes form when the outer surface of a lava flow cools and hardens while molten rock keeps moving underneath. When the lava drains away, it leaves a hollow tunnel behind. Scientists think the Marius Hills Pit could be a skylight, an opening into the roof of a tunnel like that.

There is already reason for hope. EarthSky reports that radar data from Japan's Kaguya orbiter and gravity measurements from NASA's GRAIL mission have pointed toward a void beneath the surface in this area.

How GIMLI Will Look Underground

GIMLI will not climb into the pit. Instead, it will study the ground around it with a set of tools: ground penetrating radar, seismic sensors, a gravimeter that measures tiny changes in gravity, and cameras to image the surface and the exposed pit walls. Together, the institute says, these instruments will search for an underground void and help estimate its size if one exists.

The seismic work is a return to an old idea. In the institute's announcement, Putzig said this kind of active source seismic method has "essentially not been done since the Apollo astronauts conducted the first seismic surveys on the Moon."

Even if there is no cave, the mission still has a job to do. The team says its measurements could help explain how the pit formed, and the layered walls could reveal how lava traveled across the moon and whether long stretches of time separated its eruptions.

Why a Moon Cave Matters

The open lunar surface offers no shelter from radiation, falling micrometeoroids or extreme swings in temperature. NASA says a confirmed lava tube could give future astronauts ready made protection and could shift how habitats are planned.

There is a science prize as well. "Confirming a substantial lava tube would give us an insight into how volcanism operated on the Moon," Gareth Morgan, the mission's deputy principal investigator, said in the institute's release. NASA's other two PRISM selections, a lunar environment monitoring station and an imager called DISCO, will help the agency study hazards, moonquakes and hidden ice as it plans a base near the lunar south pole.

What I Take From It

I love stories like this one. Scientists have looked at this pit from orbit for years, gathering clues and building a case. At some point, the only way to answer the question is to go and look closely.

That is a lesson worth keeping in our own lives. Research and planning matter, but there comes a moment when you have to put your instruments on the ground. I will be watching for updates on GIMLI. Share this with someone who loves space, and come back to josephbonner.com for more stories worth your time.