NASA to Probe Dark Pit on the Moon for Signs of Vast Hidden Tunnel

MARIUS HILLS, THE MOON — NASA has selected an investigation to determine what lies beneath one of the Moon's most curious openings, according to a report published by Above the Norm. The Marius Hills Pit, first identified in 2009 by Japan's Kaguya spacecraft, is believed to be an entrance to a subsurface void, probably a lava tube.

The report states that later images from NASA's Lunar Reconnaissance Orbiter showed part of the pit's floor extending beneath an overhanging roof, which it describes as confirmation that a hidden cavity exists. How far it runs remains unknown. The opening is put at roughly 65 metres across, though estimates vary.

The new project is called the Geophysical Instruments for Marius Lunar pit Investigation, or GIMLI. It is led by Nathaniel Putzig of the Planetary Science Institute, with Honeybee Robotics and other organisations taking part. It was chosen under NASA's PRISM programme, with delivery expected through the Commercial Lunar Payload Services initiative.

Rather than lowering a robot into the pit, GIMLI would probe the ground from above and around it. Ground-penetrating radar would look for boundaries between rock and empty space, seismic instruments would track vibrations, a gravimeter would seek missing mass, and cameras would study the pit walls. The article notes that agreement among all three methods would let researchers estimate the shape and extent of any cavity with greater confidence.

Earlier clues are cited. Researchers reported in 2017 that radar echoes from SELENE were consistent with an intact lava tube or other void, and gravity data from NASA's GRAIL mission showed apparently less mass at several suspect locations. The article cautions that the exact dimensions remain uncertain.

The article also stresses restraint. It says the work does not mean astronauts are preparing a base in the pit, though it notes that caves might one day offer shelter from radiation, temperature swings and micrometeoroids. The pit, it concludes, may prove only a local collapse, or the doorway to a vast tunnel sealed for billions of years.