NASA to Probe a Moon Pit for a Hidden Lava Tube

Summary:

NASA will send instruments to a pit in a volcanic plain on the Moon’s near side to find out whether it opens into a cave. The pit, in the Marius Hills complex within Oceanus Procellarum, is a steep-sided hole about 58 by 49 metres across (190 by 161 feet) and roughly 40 metres deep. Orbital measurements since 2017 have been read as consistent with a lava tube running beneath it — a drained channel left behind by flowing lava, tens of kilometres long — but nothing has been measured at the site itself.

The payload is the Geophysical Instruments for Marius Lunar pit Investigation (GIMLI), announced on 30 September 2026 as one of three selections under NASA’s Payloads and Research Investigations on the Surface of the Moon (PRISM) programme. It is led by Dr Nathaniel Putzig of the Planetary Science Institute (PSI), partnered with Honeybee Robotics and the Norwegian Space Agency, and carries an active-source seismic system, a gravimeter, a ground-penetrating radar and cameras. NASA’s release states that an underground space of this kind “could offer future astronauts ready-made protection from extreme temperatures and harmful radiation”, and that confirming one “could shift future habitat planning”.

NASA has named no launch date and no delivery provider. Its outpost planning remains directed at the lunar south pole.

Detailed Report

1. NASA Selects Three New Lunar Payloads: Two Aimed at the South Pole, One at a Volcanic Pit

NASA issued release 26-080, “NASA Adds New Science Investigations for Moon Base,” on 30 September 2026, naming three payload suites selected under the Payloads and Research Investigations on the Surface of the Moon (PRISM) programme. PRISM is how NASA picks science instruments for the lunar surface. The Commercial Lunar Payload Services (CLPS) initiative is how it delivers them, by contracting commercial companies to fly them to the Moon.

The Geophysical Instruments for Marius Lunar pit Investigation (GIMLI) will be deployed at the Marius Hills Pit, on the near side, to establish whether a lava tube lies beneath it. A tube would be the first confirmed by instruments on the lunar surface. It would also be an enclosed space, roofed by rock that blocks radiation and micrometeoroid strikes and holds a steadier temperature than the surface. That possibility has driven the study of the pit from orbit since its discovery in 2009.

The other two selections are directed at the lunar south pole, where NASA’s outpost planning is concentrated. The Lunar Environment Monitoring Station – South Pole (LEMS-SP), led by Dr Mehdi Benna of the University of Maryland, Baltimore County, will monitor micrometeoroid strikes, track volatiles drifting into the Moon’s thin outer layer of gases, and use a short-period seismometer to detect seismic events. The Depth Imager with Spectral and Color Optics (DISCO), led by Dr Ariel Deutsch of NASA’s Ames Research Center, will make the first direct surface measurements of ice held in lunar micro-cold traps and study how the ground responds to rocket exhaust and to vehicle traffic.

2. Seismic, Gravity and Radar: How the Mission Will Detect a Void Beneath the Pit

GIMLI is led by Dr Nathaniel Putzig of the Planetary Science Institute (PSI), which announced the partnership arrangements on 1 October 2026. Honeybee Robotics, a Blue Origin company, is building the active-source seismic system, the gravimeter and the cameras, and will integrate the instruments with the lander and rover. The company also provides project management and will lead surface operations jointly with PSI. The Norwegian Space Agency provides the ground-penetrating radar. Co-investigators are drawn from Boise State University, Johns Hopkins University, the Lunar and Planetary Institute and the University of Oslo.

The active-source seismic system generates seismic waves and records their passage through the ground; waves crossing an open void arrive differently from waves crossing solid rock. The gravimeter measures local variations in gravity, which fall slightly over a cavity because less mass lies beneath the instrument. The ground-penetrating radar transmits radio pulses into the subsurface and times the reflections, which return from boundaries between materials of differing density, including the roof and floor of a void. Together the three can establish whether a void extends from the pit and bound its size.

Putzig said in the PSI announcement:

“It’s long been a desire of mine to reintroduce intentional active-source seismic methods to planetary science, as it has essentially not been done since the Apollo astronauts conducted the first seismic surveys on the Moon. Combining that method with ground-penetrating radar and gravity measurements makes it all the more exciting, as these methods together will allow us to get a much better understanding of subsurface properties — including the anticipated detection of a lava tube extending away from the Marius Hills pit.”

Deputy Principal Investigator Gareth Morgan said:

“It has long been speculated that lava tubes, which on Earth are remnants of drained lava flows, exist on the Moon, but this has never been definitively confirmed. GIMLI will enable us to address this for the first time.”

The cameras will image the surface and the exposed pit walls. Those walls expose stacked lava flows and layers of regolith, the loose fragmented material covering the lunar surface, which elsewhere lie buried. Imaging that sequence gives the timing and style of the eruptions that built the region.

3. Marius Hills Pit: A 40-Metre-Deep Opening in the Ocean of Storms

The Marius Hills Pit lies in the Marius Hills volcanic complex, within Oceanus Procellarum, the “Ocean of Storms” and the largest of the dark basaltic plains on the lunar near side. The complex is an ancient volcanic region containing domes, cones and sinuous rilles, the winding channels cut or roofed by flowing lava. The pit is a steep-sided, circular-to-oval opening that sits within one of those rilles. Later measurements by the LRO Camera team, taken from images at higher Sun elevations, put it at about 58 by 49 metres across (190 by 161 feet) and about 40 metres deep (131 feet), revising earlier and larger estimates.

Japan’s SELENE spacecraft, the Selenological and Engineering Explorer, also known as Kaguya, identified the pit in 2009 in images from its Terrain Camera. NASA’s Lunar Reconnaissance Orbiter (LRO) imaged it at higher resolution with its Narrow Angle Camera, showing overhanging walls and layered structure inside the opening. A pit of this form is consistent with a skylight, a point where the roof of a lava tube has collapsed and left an opening into the space below. The interior beyond the walls has not been directly observed.

4. Orbital Radar and Gravity Data Are Consistent With a 50-Kilometre Tube

SELENE’s Lunar Radar Sounder returned echoes near the pit showing a sharp drop in signal power followed by a second peak. A 2017 paper in Geophysical Research Letters by Kaku and colleagues reported that the pattern was consistent with an intact lava tube roughly 50 kilometres long (31 miles). A companion paper by Chappaz and colleagues, using gravity maps from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission, identified mass deficits aligned with the candidate tube locations, the signature a long underground void would produce. LRO thermal observations reported in 2022 found that the interiors of lunar pits, Marius Hills among them, hold more stable temperatures than the exposed surface.

Radar has since produced direct evidence of a conduit at a different lunar pit. A 2024 paper in Nature Astronomy by Carrer and colleagues reported that a reanalysis of LRO radar data showed an accessible conduit extending from the Mare Tranquillitatis Pit, a separate site on the near side. The result establishes that the method can resolve such a structure.

At Marius Hills the evidence remains interpretation of orbital data, dependent on the models applied to the radar echoes and the gravity anomalies. The existence, extent and continuity of any tube there are unconfirmed.

5. What a Confirmed Lava Tube Would Mean for Lunar Habitat Planning

NASA’s release states that if the pit leads to a large underground space, such spaces “could offer future astronauts ready-made protection from extreme temperatures and harmful radiation,” and that confirming them “could shift future habitat planning.”

A tube at Marius Hills would not compete with the south pole for the current outpost. The pole was selected for near-continuous sunlight and proximity to water ice, neither of which the Marius Hills region offers. What confirmation would supply is the first surface-based evidence that natural shelter exists on the Moon, for use well beyond the present programme.

The shelter case itself remains untested. The roof thickness, structural integrity, radiation environment and thermal conditions inside any tube at the site are unknown, and no surface measurement has yet confirmed that a tube is there.

NASA has named no launch date and no CLPS provider for GIMLI. A report by Aerospace America on 21 October 2026 states that plans call for launching a rover in 2031.

Conclusion

GIMLI is the first funded surface investigation of the Marius Hills Pit, and the first lunar mission to carry active-source seismic equipment since Apollo. Its instruments can establish whether a void extends from the pit and bound its size; they cannot establish whether any such space is structurally sound or usable.

A result either way settles a question that has stood since 2009. Confirmation would make Marius Hills the first lava tube confirmed by measurements taken on the surface and give habitat planners a measured example of natural shelter to work from. A negative result would close a well-studied candidate identified from orbit and return the search to the other pits catalogued on the near side.