Plate Nº 11 · recorded October 16, 2026
Space & AstronomyReported finding
NASA's GIMLI mission will probe a lunar pit for hidden caves
NASA selected the GIMLI mission on September 30, 2026, to land at the Marius Hills Pit and search for a lunar lava tube that could shelter future astronauts and reveal the moon's volcanic past.
By Priya Raman3 min read683 words
In brief
- NASA selected the GIMLI mission on September 30, 2026.
- The Marius Hills Pit is roughly 90 meters across and 50 meters deep.
- Nearly 300 pits like Marius Hills have been cataloged on the moon.
- Lunar lava tubes could reach 1,260 feet (385 meters) wide, scientists estimate.
- PRISM solicited its first proposals on February 14, 2020.
NASA selected a new lunar mission on September 30, 2026, to test a hypothesis that has lingered since the Apollo era: do caves lie beneath the moon's surface?
The lander, named GIMLI (Geophysical Instruments for Marius Lunar pit Investigation), will touch down beside the Marius Hills Pit. The opening is a steep-walled circle roughly 90 meters (295 feet) across and 50 meters (164 feet) deep, set in Oceanus Procellarum, the dark basalt plain that dominates the western edge of the moon's near side.
Mission planners named the spacecraft after Gimli, the cave-faring dwarf in J.R.R. Tolkien's "The Lord of the Rings."
What will GIMLI actually do at the pit?
GIMLI will not descend into the opening. It will station itself at the rim and sweep the interior with instruments, searching for a hollow chamber below.
The payload includes a Norwegian Space Agency ground-penetrating radar, a gravimeter (a device that measures tiny local variations in gravitational pull), seismic sensors, and cameras. Than Putzig, GIMLI's principal investigator at the Planetary Science Institute, noted that this style of subsurface probing has essentially not been done on the moon since the Apollo astronauts of the 1970s.
How do lava tubes form, and why might one lie here?
On Earth, lava tubes form when the outer skin of a flowing lava stream cools and hardens while molten rock continues to move beneath it. When the lava supply stops and the channel drains, a hollow tunnel remains.
Scientists have long suspected that similar tunnels, sometimes marked at the surface by a "skylight" collapse, lie beneath the lunar crust. The pit at Marius Hills is one candidate skylight.
What is the existing evidence for lunar caves?
Researchers have cataloged nearly 300 pits like Marius Hills on the moon.
Early hints at Marius Hills came from radar data gathered by Japan's Kaguya orbiter and gravity measurements from NASA's GRAIL mission, both of which suggested a void below.
In 2024, NASA's Lunar Reconnaissance Orbiter used radar to examine a pit in Mare Tranquillitatis and reported evidence of a tube about 100 feet (30 meters) long.
On Earth, lava tubes rarely exceed 100 feet (30 meters) across. Under the moon's weaker gravity, scientists estimate lunar tubes could balloon to 1,260 feet (385 meters) wide, wide enough to enclose a small city block.
Why does confirming a lava tube matter?
Two reasons drive the mission, one practical and one scientific.
A confirmed tube could shelter future astronauts from cosmic radiation, micrometeoroids, and the brutal cold of the two-week lunar night. Shaded pits already offer mild temperatures: the floor of one pit in Mare Tranquillitatis holds steady at about 63 degrees Fahrenheit (17 degrees Celsius).
For geologists, a lunar lava tube would archive the history of ancient volcanic eruptions. Gareth Morgan of the Planetary Science Institute explained the stakes: "Confirming a substantial lava tube would give us an insight into how volcanism operated on the moon." He added that the find would let researchers apply knowledge of terrestrial (Earth-based) basalt caves to reconstruct lunar history.
What did NASA pick alongside GIMLI?
GIMLI is one of three investigations NASA selected under the Payloads and Research Investigations on the Surface of the Moon (PRISM) program, which first solicited proposals on February 14, 2020.
The other two selections:
- LEMS-SP, an autonomous south-pole station that will track micrometeoroids, volatiles (substances that easily vaporize), and moonquakes.
- DISCO, a depth imager designed to search for ice in permanently shadowed cold traps and to study how rocket exhaust and rover traffic disturb the regolith (the loose layer of dust and rock blanketing the moon).
Nicky Fox, associate administrator of NASA's Science Mission Directorate, framed the trio as groundwork for crewed outposts. She said: "NASA Science is building the ultimate interplanetary survival guide to ensure that science goes first to the lunar surface."
The agency has not announced a launch date for GIMLI.
Even if GIMLI finds no cave, it will still map the pit's structure and the volcanic past that carved it.
via subscribe.earthsky.org (Original)
More from Priya Raman
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Senior reporter covering people, launches and day-to-day practice in general science news at SciBeat.
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