Newly selected NASA mission will hunt for caves on the Moon

Once the flow stops and the lava drains away, the hollow channel remains as an underground tunnel. Scientists have long theorized that this process likely unfolded over the course of lunar geological history as well. Where terrestrial lava tubes top out at about 100 feet (30 meters) wide, studies suggest that under the Moon’s weaker gravity, tubes could reach 1,260 feet (385 m) across.

RELATED: Lunar lava tube could shelter a future Moon base No one knows for sure whether such tubes exist on the Moon, but scientists have proposed them since the Apollo era and recent evidence leans in their favor. In 2008, Japan’s Kaguya mission photographed the Marius Hills Pit, which scientists believed to be a skylight — an opening where part of a lava tube’s roof collapsed.

Since then, nearly 300 lunar pits have been identified. A 2024 analysis of a pit in Mare Tranquillitatis used radar data from NASA’s Lunar Reconaissance Orbiter to find that it might lead to an underground cavern around a hundred feet long, the first evidence of an accessible lava tube on the Moon.

And a 2017 study of the Marius Hills Pit, which paired radar data from the Kaguya orbiter with gravity measurements from NASA’s GRAIL mission, found strong evidence for a void beneath the surrounding surface, marking it as an area of interest for future exploration. What GIMLI will do Without actually entering Marius Hills Pit, GIMLI will combine a variety of instruments to search below the surface of the area around the opening and characterize what hides there, collecting the first-ever on-the-ground measurements of a lunar pit.

Pulses from the Norwegian Space Agency’s ground-penetrating radar will map subsurface objects. A gravimeter will look for missing mass where an empty chamber might sit. And seismic sensors will measure the movement of sound waves through the ground — an approach Putzig said “has essentially not been done since the Apollo astronauts” ran the Moon’s first seismic surveys.

Additionally, cameras will document what they can see of the surface and the pit’s walls. If a void exists, the combined data should help the team determine its shape and size. A confirmed lava tube would pay off on two fronts.

For future crews, it would offer protection from harmful radiation and micrometeoroids, and shield them from the Moon’s extreme temperatures. For scientists, the tube’s interior could hold its own record of the volcanic activity that carved it. As Gareth Morgan, PSI senior scientist and GIMLI’s deputy principal investigator explained, “Confirming a substantial lava tube would give us an insight into how volcanism operated on the Moon.

Lava tubes are a common feature of basaltic volcanism on Earth, so identifying them on the Moon means we could use knowledge of such terrestrial caves to better understand lunar history.” The Gimli of Tolkien lore discovered a sprawling cave system which he described to his elven companion as, “chamber after chamber, Legolas; hall opening out of hall, dome after dome, stair beyond stair.” It’s far too soon to know whether PSI’s GIMLI will find such a cavernous complex beneath Marius Hill Pit, but a null result wouldn’t be a bust.

Even with no cave, the measurements could still uncover how the pit formed and provide the team with a more detailed understanding of the geologic and volcanic history of the Moon. Other PRISM picks GIMLI shares the PRISM selection with two other mission proposals . Lunar Environment Monitoring Station – South Pole (LEMS-SP), led by Mehdi Benna of the University of Maryland, Baltimore County, is an unmanned hazard-monitoring station that will log micrometeoroid strikes, track the amount of volatiles in the Moon’s lunar exosphere, and listen for moonquakes with a seismometer — data meant to keep future Moon Base hardware safe.

Depth Imager with Spectral and Color Optics (DISCO), led by Ariel Deutsch of NASA’s Ames Research Center, will make the first in-situ measurements of ice in the Moon’s micro cold traps (the smallest but most abundant permanently shaded regions of the Moon, measuring 1 kilometer or less in size) — data that will eventually help NASA turn lunar ice into a usable resource.

DISCO will also conduct tests on the lunar surface, investigating how it reacts to rocket exhaust and how firm it is for rovers. The announcement comes as NASA is ramping up its focus on the Moon with the Artemis program and plans for a permanent Moon base . The latter, now in the first of three phases , has several missions on the immediate horizon.

Moon Base I will send Blue Origin’s Blue Moon Mark 1 lander to the Shackleton Connecting Ridge near the south pole to study how engine plumes disturb lunar soil. Moon Base II will deliver Astrolab’s FLIP rover to Mons Mouton aboard a Griffin lander. And Moon Base III will carry Lunar Vertex , the first payload awarded under PRISM, to the lunar swirl at Reiner Gamma on Intuitive Machines’ Nova-C lander.

All three missions were originally targeting launch in 2026, but NASA has yet to release any firm launch windows. Brooks Mendenhall is a staff writer at Astronomy, based in Chattanooga, Tennessee, fueled by an unending curiosity about the universe. A former classroom teacher, he has a knack for breaking down complex concepts for a wide audience.