Mysterious Hole on the Moon May Lead to a Giant Lunar Cave

The project will receive funding through NASA’s Lunar Payloads and Research (PRISM) program. PRISM missions send scientific instruments to the lunar surface aboard spacecraft supplied by providers participating in the Commercial Lunar Payload Services (CLPS) initiative.

GIMLI will investigate the Marius Hills Pit

The selected project, called the Geophysical Instrument for Marius Lunar Pit Investigation (GIMLI), is led by Tan Putzig, PSI’s associate director and senior scientist. PSI is working with Honeybee Robotics, which will build much of the mission’s equipment and instrumentation. The instruments will travel aboard landers and rovers provided through the CLPS initiative. PSI is also partnering with the Norwegian Space Agency.

“GIMLI represents the ambitious planetary science that PSI was founded to pursue,” said PSI Director and CEO Amanda Hendricks. “Tan and his team have taken scientific questions that we have been studying from orbit and developed a way to investigate them directly on the Moon. We are thrilled that PSI will be leading this effort and partnering with NASA and Honeybee Robotics to learn more about the Moon and its volcanic past.”

Scientists studying the Moon from orbit have found strong evidence that caves and lava tubes may lie beneath its surface. GIMLI will focus on the Marius Hills Pit (MHP), a large opening in one of the Moon’s most volcanically diverse regions. Like other lunar holes, the MHP could provide access to underground structures formed by ancient volcanic activity.

GIMLI will allow researchers to study the Marius Hills Pit directly from the lunar surface instead of relying solely on observations from orbit.

Radar and seismic sensors will search for lunar lava tubes

“It has been a long-standing desire of mine to reintroduce intentional active-source seismology to planetary science; it has essentially not been done since the Apollo astronauts conducted the first seismic surveys on the Moon,” Putzig said. “Combining that method with ground-penetrating radar and gravity measurements makes it even more exciting, because these methods combined will allow us to better understand subsurface properties, including the anticipated detection of lava tubes extending from the Marius Hills Pit.”

To investigate what lies beneath the surface, GIMLI will combine ground-penetrating radar, seismic sensors and gravimeters. A camera will also photograph the lunar surface and the exposed walls of the pit. Together, these instruments will help scientists investigate whether underground cavities extend from the MHP and estimate their dimensions if they are found.

Honeybee Robotics, a commercial partner of PSI and a Blue Origin company, will provide project management services and build active seismic systems, gravimeters and camera instrumentation. The company will also help integrate the scientific instruments into landers and rovers. PSI and Honeybee Robotics will jointly lead equipment operations after the spacecraft reaches the lunar surface.

GIMLI could reveal new details about lunar geology

Even if researchers do not find caves or lava tubes, the mission could still produce important discoveries. Its measurements could help answer a major question: How did the Marius Hills Pit form?

Studying the materials surrounding and beneath the MHP could provide new clues about the pit’s origins, as well as the geology and volcanic history of the wider region.

The research team also plans to examine other possible underground structures. The surrounding area has a long history of volcanic activity, and the walls of the MHP expose layers of regolith and lava flows that are normally buried. Studying these layers could reveal how lava once moved across and beneath the Moon’s terrain, and whether individual eruptions were separated by long intervals.

The Marius Hills Pit is valuable not only because its walls expose hidden geology. Any underground spaces connected to the pit could also preserve evidence of the volcanic activity that helped shape the Moon.

A window into the Moon’s volcanic past

“Identification of substantial lava tubes would provide insight into how volcanic activity occurred on the Moon,” explained Gareth Morgan, a senior scientist at PSI and co-principal investigator of the GIMLI program. “Lava tubes are a common feature of basaltic volcanism on Earth, so identifying lava tubes on the lunar surface means we may be able to use knowledge of such terrestrial caves to better understand the Moon’s history.”

In addition to PSI and Honeybee Robotics, the GIMLI team includes collaborators from Boise State University, Johns Hopkins University, the Lunar and Planetary Institute and the University of Oslo. The Norwegian Space Agency will provide the ground-penetrating radar.