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NASA selects a PSI-led team to sound for a lava tube beyond the Marius Hills pit
NASA picked a Planetary Science Institute team to test whether the Moon's Marius Hills pit opens into a lava tube, with a commercial lander and rover. PSI says such a cave could one day shelter astronauts from radiation and extreme temperature swings.
The Scientist · Science desk
What happened
- The Marius Hills pit is a large hole in one of the Moon's most volcanically diverse regions and may open into spaces formed by ancient volcanism.
- Than Putzig, an associate director and senior scientist at PSI, leads the project, called the Geophysical Instruments for Marius Lunar pit Investigation, or GIMLI.
- Honeybee Robotics, a Blue Origin company, is building the seismic system, gravimeter and cameras, integrating them, and will run surface operations with PSI.
- The Norwegian Space Agency is a partner in the work and is supplying the ground-penetrating radar.
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Why it matters
- capability Seismic, radar and gravity readings taken at the pit can confirm a void and estimate its extent, a size figure that any argument for sheltering crews there would have to start from.
- decision NASA has backed a payload whose scientific return survives a null result, because the same subsurface data bear on how the pit formed.
- precedent A working active-source survey at Marius Hills would give later lunar surface missions a tested way to image the ground beneath a landing site.
The case for a cave at Marius Hills rests so far on observations from lunar orbit. PSI calls them "compelling evidence" that caves and lava tubes may exist beneath the Moon's surface [9]. That evidence establishes a possibility. Whether a potentially large void actually extends beyond the pit's opening is the question NASA selected GIMLI to answer [1]. "Than and his team are taking a scientific question we've been studying from orbit and have developed a way to investigate it directly on the moon," said Amanda Hendrix, PSI's director and CEO [8].
The survey looks underground three ways [1]. One is an active-source seismic system, in which the team generates the seismic signal on purpose. The others are ground-penetrating radar and a gravimeter, while cameras image the surface and the pit walls [14]. The aim is to find a void extending from the pit and, if one exists, to help determine its size [14]. Putzig said the methods together "will allow us to get a much better understanding of subsurface properties" [12].
He also spoke of "the anticipated detection of a lava tube extending away from the Marius Hills pit" [13].
The seismic method has a history on the Moon. "It's long been a desire of mine to reintroduce intentional active-source seismic methods to planetary science, as it has essentially not been done since the Apollo astronauts conducted the first seismic surveys on the moon," Putzig said [11].
If no cave turns up, measurements of the surrounding subsurface could still help explain how the pit formed and the geology and volcanic history of the site [15]. The pit walls expose layers of regolith and lava flows that are usually hidden underground. The team will study them for how lava traveled and whether long periods separated eruptions [16]. A confirmed tube would add a comparison with Earth. "Lava tubes are a common feature of basaltic volcanism on Earth, so identifying them on the moon means we could use knowledge of such terrestrial caves to better understand lunar history," said Gareth Morgan, a PSI senior scientist and the program's deputy principal investigator [17].
Even a clean detection would not show whether the cave could make a workable shelter. PSI's wording is that such a cave "may one day" provide a safe haven [2]. The announcement did not disclose what size of void would qualify, the lander provider, a launch date or a cost [4].
What to watch
- NASA naming the CLPS provider and a delivery date for the lander and rover carrying GIMLI.
- First results from the seismic, radar and gravity survey on whether a void extends from the pit, and how large it is.
- Whether the team states what void size would make a cave at Marius Hills useful as crew shelter.