NASA selects GIMLI to scan Marius Hills Pit for lunar lava tube

NASA selected GIMLI, led by the Planetary Science Institute with principal investigator Nathaniel Putzig, on Sept. 30, 2026, as one of three PRISM payload suites for the Moon Base Program to scan beneath the Marius Hills Pit on the Moon for a lava tube.

GIMLI will be deployed at the Marius Hills Pit to scan below the surface and determine whether the pit leads into a large underground lava tube that could shelter astronauts from extreme temperatures and harmful radiation. NASA said the work aids understanding of fundamental lunar volcanic processes. EarthSky and Space Daily report that the suite combines a ground-penetrating radar supplied by the Norwegian Space Agency with a gravimeter, seismic sensors and cameras.

NASA said confirming such voids could shift planning for future habitats by offering natural shelters that keep temperatures stable and protect against radiation and micrometeoroid bombardment. Gareth Morgan, the suite’s deputy principal investigator, said confirming a lava tube would reveal how volcanism operated on the Moon, as lava tubes are common features of basaltic volcanism on Earth.

EarthSky reports that the Marius Hills Pit lies in the Marius Hills volcanic region in Oceanus Procellarum, a dark lava plain or lunar mare on the western edge of the Moon’s near side, and is about 295 feet (90 meters) across and approximately 164 feet (50 meters) deep.

Published depth estimates disagree: NASA’s orbiter image description lists about 34 meters, the Lunar Reconnaissance Orbiter Camera team’s 2017 update puts it at 40 meters, principal investigator Nathaniel Putzig estimates about 60 meters, and EarthSky gives approximately 50 meters. High-resolution Lunar Reconnaissance Orbiter images show overhanging walls above a subsurface void wider than the pit’s diameter, though the void’s size is unknown and it is unclear whether it stands alone or forms part of a larger cave system.

NASA’s PRISM program aims to minimize risks to astronauts and maximize agency goals by delivering science investigations and technology payloads to the lunar surface ahead of crewed missions. Nicky Fox, associate administrator for the Science Mission Directorate, said the selections will help minimize risks to astronauts while advancing the first lunar outpost in preparation for sending astronauts to Mars. The Sept. 30, 2026 NASA release said confirming such voids could change planning for future habitats by offering natural shelters that keep temperatures stable and protect against radiation and micrometeoroid bombardment.

The other two PRISM selections are LEMS-SP, led by Mehdi Benna of the University of Maryland, Baltimore County, to track micrometeoroids, volatiles and moonquakes near the south pole, and DISCO, led by Ariel Deutsch of NASA’s Ames Research Center, to measure ice in micro-cold traps. NASA selected all three suites through PRISM to fly via Commercial Lunar Payload Services as part of the Moon Base Program, each with a named principal investigator.

NASA’s Commercial Lunar Payload Services initiative will deliver the GIMLI payload to the lunar surface as part of the agency’s accelerated cadence of lunar missions. No launch date and no lander vendor have been named for the GIMLI delivery, even though the suite was announced on Sept. 30, 2026 as one of three PRISM payloads for Moon Base to fly on a commercial lander under CLPS.

NASA’s Lunar Reconnaissance Orbiter used radar in 2024 to investigate the Mare Tranquillitatis pit, and the data suggested a possible lava tube about 100 feet long. In 2017, researchers using the Lunar Radar Sounder aboard Japan’s Kaguya spacecraft detected echoes near the Marius Hills Pit and read them as signs of an intact lava tube; possible tube locations also match mass deficits in GRAIL gravity maps, but nothing proves the pit leads anywhere. Subsurface scanning of this kind has essentially not been done since the Apollo astronauts in the 1970s, according to principal investigator Nathaniel Putzig.

Scientists estimate lunar lava tubes could reach 1,260 feet (385 meters) across because of the Moon’s weaker gravity, compared with Earth tubes of about 100 feet (30 meters), and nearly 300 pits like Marius Hills Pit exist on the Moon. Many of those pits are potential candidates for subsurface lava tubes. Dr. Don Platt, director of the Spaceport Education Center at Florida Tech, said underground caves could shield astronauts from dangerous radiation and fast-moving micrometeoroids. “A cave could provide shelter or shielding if you will,” Platt said.

EarthSky says GIMLI takes its name from Gimli, the cave-loving dwarf in J.R.R. Tolkien’s The Lord of the Rings. NASA released its first PRISM call for proposals on Feb. 14, 2020. NASA’s PRISM program selected GIMLI as part of its broader Moon Base Program, which aims to establish a permanent lunar outpost and prepare for crewed Mars missions.