The mission, known as the Geophysical Instruments for Marius Lunar pit Investigation, or GIMLI, is led by Than Putzig, Associate Director and Senior Scientist at the Planetary Science Institute. PSI is partnering with Honeybee Robotics, a Blue Origin company, which will build much of the equipment and instrumentation and help integrate it onto a lander and rover supplied through the CLPS initiative. The effort will also be carried out in partnership with the Norwegian Space Agency, which is providing the mission’s ground-penetrating radar. Co-Investigators from Boise State University, Johns Hopkins University, the Lunar and Planetary Institute, and the University of Oslo round out a team that spans two continents and multiple disciplines.

The target of the investigation is the Marius Hills Pit, a large hole punched into one of the most volcanically diverse regions on the Moon. Like other lunar pits discovered by orbiting spacecraft, MHP may be a skylight, an opening into a subsurface cavity that formed during ancient volcanic activity. From orbit, scientists have gathered compelling evidence that caves and lava tubes may thread their way beneath the Moon’s surface, but orbital data alone cannot settle the question of what lies beyond the pit’s rim. GIMLI is designed to find out directly, by measuring the subsurface from the ground for the very first time at this site.

Putzig, who has spent much of his career probing planetary interiors with radar and geophysical methods, described the mission as the fulfillment of a long-held ambition. He noted that it has long been a desire of his to reintroduce intentional active-source seismic methods to planetary science, a technique that has essentially not been used since the Apollo astronauts conducted the first seismic surveys on the Moon more than five decades ago. Combining that method with ground-penetrating radar and gravity measurements, he explained, will allow the team to achieve a much better understanding of subsurface properties, including the anticipated detection of a lava tube extending away from the Marius Hills pit.

The technical approach is a masterclass in complementary geophysics. Ground-penetrating radar will transmit electromagnetic pulses into the regolith and record the echoes returned by buried boundaries between rock layers, revealing changes in composition and structure at shallow depths. Seismic sensors, energized by an active source rather than waiting for natural moonquakes, will measure how elastic waves travel through the ground, exposing voids and density contrasts that radar might miss. A gravimeter will detect the minute gravitational signature of an empty space beneath the surface, since a large cavity produces a measurable local deficit in mass. Cameras, meanwhile, will image the surface terrain and the exposed walls of the pit itself, tying the subsurface measurements to visible geology.

Together, these instruments will not only search for an underground void extending from the Marius Hills Pit; if such a void exists, they will also help determine its size. That distinction matters enormously for future human exploration. A cave large enough to shelter hardware and habitats would be a strategic asset for any long-term lunar presence, offering protection from radiation, micrometeorite impacts, and the roughly 300-degree Celsius temperature swings between lunar day and night. Confirming the dimensions and stability of such a space from the surface would transform it from an orbital curiosity into a mapped destination.

Honeybee Robotics will serve as the commercial partner to PSI, providing project management services and building the instrumentation for the active-source seismic system, the gravimeter, and the cameras. The company will also work to integrate all of the instruments onto the lander and rover and, together with PSI, will lead their operations on the lunar surface. The division of labor reflects a growing model in lunar exploration, in which government scientists team up with commercial aerospace firms to fly sophisticated payloads on robotic missions at a fraction of the cost of traditional flagship programs.

Crucially, the mission’s scientific value does not hinge entirely on finding a cave. Even if GIMLI fails to detect a lava tube beneath the surface, the data it collects could still resolve an important mystery: how did the pit form in the first place? Measurements of the surrounding subsurface will speak to the origin of MHP and provide a far better understanding of the geology and volcanic history of the site. The pit walls themselves expose layers of regolith and lava flows that are normally hidden underground, and studying those layers could reveal how lava once traveled across the Moon and whether long stretches of time separated successive eruptions.

The team is also looking beyond the pit itself. The Marius Hills region preserves a long history of volcanic activity, and the interiors of any potential underground spaces could hold a record of the processes that shaped the Moon’s volcanic plains. Gareth Morgan, PSI Senior Scientist and Deputy Principal Investigator on the GIMLI program, explained that confirming a substantial lava tube would give scientists insight into how volcanism operated on the Moon. Lava tubes are a common feature of basaltic volcanism on Earth, he noted, so identifying them on the Moon means researchers could apply knowledge of such terrestrial caves to better understand lunar history.

For the Planetary Science Institute, the selection marks a milestone in its evolution from an organization known primarily for orbital data analysis to one leading surface operations on another world. PSI Director and CEO Amanda Hendrix called GIMLI the type of ambitious planetary science that PSI was built to pursue, saying that Putzig and his team have taken a scientific question the institute has been studying from orbit and developed a way to investigate it directly on the Moon. She expressed excitement about partnering with NASA and Honeybee Robotics to learn more about the Moon and its volcanic past. If the instruments perform as designed, humanity may soon peer, for the first time, into the hidden architecture beneath one of the Moon’s most enigmatic openings, and perhaps take an early step toward making a lunar cave humanity’s first off-world shelter.

Subject of Research: Investigation of a potential lunar lava tube at the Marius Hills Pit using surface geophysical instruments under NASA's PRISM program

Article Title: PSI-led team selected for NASA PRISM program to explore potential lunar cave

Article References: PSI-led team selected for NASA PRISM program to explore potential lunar cave. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Moon, lunar caves, lava tubes, Marius Hills Pit, NASA PRISM, CLPS, Planetary Science Institute, Honeybee Robotics, ground-penetrating radar, seismology, gravimetry, lunar volcanism

The case for concern rests on the peculiar character of both the Moon and its soil. The lunar surface combines an almost total vacuum, one-sixth of Earth’s gravity, extreme temperature swings between day and night, intense ionizing radiation, electrostatic charging driven by solar wind and ultraviolet light, and continuous micrometeoroid bombardment. These conditions have shaped regolith into a material unlike anything quarried on Earth: highly angular, poorly sorted, and cohesive in ways that make it reluctant to flow. Prior studies have shown that the sharp particle shapes produce poor flowability that could jam hoppers and silos, while solar-wind charging combined with weak charge dissipation in vacuum can levitate fine particles, creating dust clouds that contaminate optics, abrade seals, and threaten astronaut health. Apollo-era experience with lunar dust, which degraded camera lenses, thermal surfaces, and spacesuits, offers a cautionary preview of what awaits full-scale mining and processing hardware.

Earth-based experiments currently fill the gap as best they can. Researchers use parabolic flights and drop towers to approximate reduced gravity, thermal vacuum chambers to approximate the exosphere, and increasingly sophisticated regolith simulants to stand in for the real thing, while Discrete Element Method, or DEM, computer simulations model particle-by-particle behavior numerically. But the authors point out a fundamental circularity: none of these approaches has ever been validated against actual lunar regolith handled under actual lunar conditions, because no such dataset exists. Existing simulants were largely developed for spectroscopic or chemical-process work, and their material handling characteristics were rarely a design priority. There is, the authors note, no standardized record of basic handling parameters such as flow functions in simulant property databases. The result, documented in international gap assessments, is a substantial risk that equipment designed on Earth will fail or underperform the first time it digs into the real thing.

To address this, the team proposes a pragmatic rather than purely scientific strategy. Instead of measuring fundamental material properties with laboratory precision, the payload would demonstrate and observe eight practical handling processes expected in a future lunar economy: excavation, conveying, sorting, dynamic handling, static handling, electrostatic separation, pile forming, and compaction. The reasoning is that watching real regolith move through machinery that resembles future flight hardware yields both the validation data that Earth-based simulations need and a direct de-risking of the mechanisms themselves. Each subsystem doubles as a technology demonstration, raising the technology readiness level of components that future missions will depend on, while simultaneously generating video observations from which fundamental flow parameters can be derived.

The proposed architecture arranges these eight subsystems in a single cascading sequence, with the output of each process feeding the next, a choice made to minimize mass and volume within the envelope of commercial lunar landers. The sequence begins with a continuous bucket-wheel excavator mounted on a deployable arm, chosen over discrete diggers for its steady material flow and predictable scaling behavior. Excavated regolith is lifted by a two-stage screw conveyor, selected for mechanical simplicity and tolerance of gravity variations, to the top of a gravity-fed stack. There the material first passes through a vibratory sieve carousel, which can either size-separate particles or be bypassed, then into a transparent-walled rotating drum with adjustable speed for studying dynamic flow regimes, next into a wedge hopper with adjustable wall angles and outlet width for static handling tests, past a pair of planar electrodes that generate electric fields across the falling regolith stream, and finally onto a flat plate where pile formation is recorded and a linear actuator applies controlled compression, mimicking brick-making and foundation compaction.

Observation throughout relies on non-contact optical imaging rather than distributed sensor networks. Up to eight cameras, potentially supplemented by a single hyperspectral camera for chemical and mineralogical context, would record every process, an approach the authors argue simplifies development and directly de-risks the video-based process control techniques that full-scale lunar plants will eventually need. Crucially, the payload would also carry roughly five samples of terrestrial regolith simulants, each a few hundred grams, dispensed from a carousel into the processing chain. Watching familiar simulants behave, or misbehave, beside real lunar material under real lunar conditions is what turns the payload from a demonstration into a calibration instrument: any divergence between simulant and native regolith tells modelers exactly how much to trust their Earth-based results. The carousel also provides redundancy, since if excavation fails, the mission can still proceed using delivered samples.

Order-of-magnitude engineering suggests the concept is feasible with current commercial capabilities. The vertically oriented payload is estimated at 79 kilograms with a maximum dimension of 1.6 meters, a peak power draw of 95 watts per experimental cycle, and a data budget dominated by video: roughly 655,000 megabits per full run of eight cameras, compressible below 108,000 megabits and downloadable in about three hours at 10 megabits per second. As a delivery case study, the team examined Firefly Aerospace’s Blue Ghost lander, which offers 150 kilograms of payload capacity at an estimated cost of around one million dollars per kilogram to the lunar surface. Accommodating the payload’s tall gravity-fed stack and its surface-reaching excavator requires combining two of Blue Ghost’s payload bays, but the study’s indicative computer-aided design shows the configuration fits.

Mission planning assumes a static lander at low to mid latitudes, designed to survive the lunar night, operating across six lunar days. A single day of operations proved too little to return meaningful data, so the baseline plan divides the mission into phases: commissioning during the first day, then repeated 96-hour experimental cycles in which each four-hour sample-handling sequence is followed by downlink, ground analysis, and refinement of the next run. Over six lunar days, the payload could complete sixteen experimental cycles, processing sixteen samples in an iterative fail-fast loop that mirrors the agile development philosophy the authors advocate for the payload’s construction. Landing site selection involves a trade-off between the scientifically compelling but poorly characterized lunar south pole, where future ISRU activity will concentrate, and previously visited regions where existing ground-truth regolith data would allow direct comparison, and future variants could add fetch rovers to sample across kilometer scales.

Beyond validation, the study identifies three collateral payoffs: practical knowledge of dust generation, transport, and mitigation, including testing wipers, electrostatic repellers, and optical coatings on the cameras themselves; early measurement of mechanical wear on handling hardware in the abrasive lunar environment, using wear indicators, power monitoring, and vibroacoustic sensing; and the elevation of technology readiness for a suite of components future missions would otherwise fly unproven. The authors present the paper explicitly as a conversation starter, inviting the community to debate the approach, refine the design, and pursue laboratory breadboards of the subsystems for testing in vacuum and parabolic-flight facilities. If the concept survives that scrutiny, it could split into smaller sub-payloads distributed across multiple lander missions. Either way, the argument lands squarely: before humanity mines the Moon, it should first learn how the Moon’s dust actually moves, and the cheapest way to find out is to ship a small factory’s worth of handling hardware to the surface and watch.

Subject of Research: In situ validation and calibration of lunar regolith granular materials handling for future lunar in-situ resource utilization.

Article Title: Outline case for a payload and mission scenario to perform in situ de-risking, validation and calibration of lunar granular materials handling

Article References: Pratnekar, M., Cilliers, J. J., Crawford, I. A., Hadler, K., Hartlieb, P., Joy, K. H., Patel, M. R., Saydam, S., Sureda, M., Bardaux, M., Castagnaro, D. B., Diakonikolis, M., Fossey, J., Gee, M. J., Jhamb, E., Kanda, B., Marechal, Q., Monteiro, N., Ray, T., … Cullen, D. C. (2026). Outline case for a payload and mission scenario to perform in situ de-risking, validation and calibration of lunar granular materials handling. Space and Planetary Resources, 2(1), Article 1. https://doi.org/10.1007/s44461-026-00006-x

Image Credits: AI Generated

DOI: 10.1007/s44461-026-00006-x

Keywords: lunar regolith, in-situ resource utilization, granular materials handling, reduced gravity, lunar lander, payload design, discrete element method, regolith simulants, lunar dust, CLPS, Blue Ghost, lunar ISRU