The hole is the Mare Tranquillitatis pit, a steep-sided opening on the Moon’s Sea of Tranquility. Radar data suggest it may lead to an underground passage tens of metres long—but scientists have not directly explored the passage or established its full size.
Where is the hole on the Moon?
The Mare Tranquillitatis pit lies in the Moon’s Sea of Tranquility, about 230 miles northeast of the first human lunar landing site, according to NASA’s 2024 summary. The visible pit is an opening in the surface; the possible cave is a separate feature inferred below it.
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What evidence suggests there is a cave?
A 2024 study in Nature Astronomy reanalyzed radar images collected in 2010 by Mini-RF, an instrument aboard NASA’s Lunar Reconnaissance Orbiter. The researchers found reflections consistent with a subsurface conduit extending tens of metres from the pit. Their work supports the presence of a cave-like passage, but it is not a photograph or a direct survey of the underground feature. Read the study in Nature Astronomy.
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NASA describes the inferred segment as extending more than 200 feet from the pit’s base. That figure is not the cave’s measured total length: its full extent remains unknown. LRO project scientist and NASA Goddard Space Flight Center scientist Noah Petro said, “Now the analysis of the Mini-RF radar data tells us how far these caves might extend.” NASA’s report presents the result as evidence about how far a passage might reach, not a complete map.
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What is known—and what remains uncertain?
- Observed: A steep-sided pit at Mare Tranquillitatis.
- Inferred from radar: A cave-like conduit tens of metres long, including a segment NASA describes as more than 200 feet from the pit base.
- Not established: The passage’s total length, shape, volume, structural condition, or whether a rover or people could safely enter it.
The distinction matters: evidence for a passage does not establish that the entire cave is “giant,” accessible, or suitable for habitation. The radar finding is a reason to investigate further, not proof of a ready-made shelter.
How might the pit and passage have formed?
One plausible explanation is that the pit formed when part of a lava-tube roof collapsed. Lava tubes can develop as molten rock flows beneath a cooled crust and later drains away, leaving a hollow passage. A roof collapse could expose part of that hollow from the surface.
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This is a possible mechanism, not a confirmed account of this pit’s history. NASA’s 2014 overview of lunar pits cautions that images alone provide little basis for determining the cause of an individual pit. That overview cataloged more than 200 pits at the time; the figure is historical, not a current census.
Could a lunar cave provide shelter?
Subsurface cavities are scientifically interesting and could matter to future exploration, but the evidence does not show that this particular passage is habitable or ready for a crewed base. NASA’s 2022 thermal analysis modeled the Mare Tranquillitatis pit at approximately 100 metres deep and found its permanently shadowed reaches stay near 17°C. Those figures describe the pit and its modeled shadowed areas—not a direct temperature measurement inside the inferred cave. A cave extending from the pit might have a similarly stable environment, but that remains conditional.
Whether the conduit could provide practical shelter would depend on questions not answered by the radar interpretation, including its structural stability, access, and radiation conditions. The cited findings establish none of those for this specific passage.
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