NASA Funds Mission to Explore Possible Lunar Cave System Using Ground-Based Instruments

Mission Overview: GIMLI Takes Direct Approach to Lunar Cave Investigation

NASA has selected a proposal from the Planetary Science Institute to investigate whether a substantial underground cavern exists beneath a lunar pit opening. The selected project, called the Geophysical Instruments for Marius Lunar pit Investigation (GIMLI), will deploy scientific instruments to the Moon's surface through NASA's Payloads and Research Investigations on the Surface of the Moon (PRISM) program, which utilizes commercial lunar landers and rovers from the Commercial Lunar Payloads Services (CLPS) initiative. Led by PSI Associate Director and Senior Scientist Than Putzig, the mission marks a significant advancement in planetary science methodology by moving from orbital observation to direct surface-based investigation.

Scientific Instruments and Detection Strategy

GIMLI will employ a sophisticated multi-instrument approach to search for underground voids and map subsurface geology. The mission will combine ground-penetrating radar, active-source seismic sensors, and gravimetry measurements—techniques that represent a return to methods last employed during the Apollo missions' lunar surface work. Cameras will document the lunar surface and the exposed walls of the Marius Hill Pit (MHP), a large opening located within one of the Moon's most volcanically varied regions. These complementary instruments working together will allow researchers to detect potential underground structures, estimate their dimensions, and analyze subsurface properties that remain hidden from orbital surveys. The active-source seismic system represents a particularly ambitious component, as intentional seismic investigations have been largely absent from planetary science missions for decades.

Partnership Structure and Equipment Development

Honeybee Robotics, a Blue Origin subsidiary, serves as the primary commercial partner, providing project management and constructing much of the mission's critical instrumentation including the seismic system, gravimeter, and camera systems. The company will also integrate scientific instruments onto the delivery lander and rover, and will lead operational duties once the spacecraft reaches the lunar surface. The broader team includes investigators from Boise State University, Johns Hopkins University, the Lunar and Planetary Institute, and the University of Oslo, with the Norwegian Space Agency contributing the ground-penetrating radar system. This collaborative structure combines academic expertise with commercial aerospace capabilities.

Why Marius Hill Pit Matters

The Marius Hill Pit represents an ideal scientific target because orbital observations have revealed compelling evidence that caves and lava tubes could exist beneath the Moon's surface. The pit's location within a volcanically varied region provides multiple scientific opportunities. If a substantial lava tube exists, it would offer crucial insights into how the Moon's internal volcanic processes operated billions of years ago. The pit's opening could represent an entrance to underground structures created during ancient volcanic activity, similar to lava tubes found on Earth that form during basaltic eruptions. Beyond the potential cave itself, the pit's exposed walls reveal layers of regolith and ancient lava flows normally buried beneath the lunar surface, providing a natural cross-section of geological history.

Broader Scientific Returns

Even if researchers find no evidence of underground caverns, the mission promises significant scientific discoveries. Detailed subsurface measurements could help explain how the Marius Hill Pit formed in the first place, addressing a fundamental question about lunar geology. By examining the material composition and structure around and beneath the pit, scientists could trace the Moon's volcanic history and understand how eruptions were spaced across time. The exposed geological layers within the pit walls could reveal patterns of lava flow movement and provide clues about volcanic mechanisms that shaped the lunar landscape. These findings would enhance understanding of the Moon's thermal and geological evolution.

Practical Implications for Future Lunar Exploration

Beyond scientific curiosity, confirming a substantial lava tube would have practical implications for human exploration. Underground caverns could eventually provide astronauts with natural protection from intense cosmic radiation and the extreme temperature swings experienced on the lunar surface, where daytime temperatures exceed 120 degrees Celsius and nighttime temperatures plunge below minus 170 degrees Celsius. Such discoveries would inform planning for future long-duration lunar habitats and research stations. The knowledge gained about lunar lava tubes could be directly applied to terrestrial geology, since similar basaltic cave systems exist on Earth and studying their lunar counterparts could improve understanding of volcanic processes across worlds.