NASA picks surface geophysics mission to probe for cave beneath lunar pit

NASA has selected a proposal led by the Planetary Science Institute to find out whether a large underground cave extends beyond the opening of a lunar pit. A cave of that kind could one day shelter astronauts from the radiation and extreme temperature swings at the lunar surface. The project will be funded through NASA's Payloads and Research Investigations on the Surface of the Moon (PRISM) program, which sends scientific instruments to the Moon on spacecraft supplied by Commercial Lunar Payload Services (CLPS) providers.

The selected project is the Geophysical Instruments for Marius Lunar pit Investigation, or GIMLI, led by PSI Associate Director and Senior Scientist Than Putzig. PSI is partnering with Honeybee Robotics, which will build much of the equipment and instrumentation to be carried on a CLPS lander and rover. The PSI work will be carried out in partnership with the Norwegian Space Agency.

PSI Director and CEO Amanda Hendrix said GIMLI is the kind of ambitious planetary science the institute was built to pursue, and that Putzig and his team have taken a question studied from orbit and developed a way to investigate it directly on the Moon.

Observations from lunar orbit have provided strong evidence that caves and lava tubes may exist beneath the Moon's surface. GIMLI will focus on the Marius Hills Pit (MHP), a large hole in one of the Moon's most volcanically diverse regions. Like other lunar pits, MHP may be an opening to underground spaces that formed during ancient volcanic activity.

GIMLI will allow scientists to investigate MHP directly from the lunar surface.

Putzig said he has long wanted to bring intentional active-source seismic methods back to planetary science, and that combining the method with ground-penetrating radar and gravity measurements makes the project more exciting still.

The mission will use ground-penetrating radar, seismic sensors and a gravimeter to look beneath the surface, with cameras imaging the surface and the pit walls. Together the instruments will search for an underground void extending from MHP and, if one exists, help determine its size.

Honeybee Robotics, a Blue Origin company, will serve as PSI's commercial partner, providing project management and building the instrumentation for the active-source seismic system, the gravimeter and the cameras. It will also integrate all instruments onto the lander and rover and, together with PSI, lead their operations on the lunar surface.

Even if GIMLI finds no cave or lava tube, its data could still help answer how the pit formed. Measurements of the surrounding subsurface could shed light on the origin of MHP and improve understanding of the geology and volcanic history of the site.

The team will also look beyond the pit itself. The area has a long history of volcanic activity, and the walls of MHP expose layers of regolith and lava flows that are usually hidden underground. Studying those layers could show how lava traveled on the Moon and whether long periods separated eruptions.

Lunar pits are of interest for more than the geology preserved in their walls. The interiors of any underground spaces could also preserve a record of the volcanic processes that shaped the Moon.

PSI Senior Scientist and Deputy Principal Investigator Gareth Morgan said confirming a substantial lava tube would give insight into how volcanism operated on the Moon. He noted that lava tubes are a common feature of basaltic volcanism on Earth, so identifying them on the Moon would allow knowledge of terrestrial caves to be used to better understand lunar history.

Beyond PSI and Honeybee Robotics, the team includes co-investigators from Boise State University, Johns Hopkins University, the Lunar and Planetary Institute and the University of Oslo, with the ground-penetrating radar provided by the Norwegian Space Agency.

CONTACT: Samantha Riestenberg, Planetary Science Institute, [email protected]