A lava tube entrance near the Moon’s north pole?

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Philolaus Crater near lunar north pole

In reviewing Lunar Reconnaissance Orbiter data scientists think they have discovered several skylight entrances into a lava tube that is located near the Moon’s north pole.

The new pits were identified on the northeastern floor of Philolaus Crater, a large, 43 mile (70 km)-diameter impact crater located at 72.1oN, 32.4oW, about 340 miles (550 km) from the North Pole of the Moon, on the lunar near side. The pits appear as small rimless depressions, typically 50 to 100 feet across (15 to 30 meters), with completely shadowed interiors. The pits are located along sections of winding channels, known on the Moon as “sinuous rilles,” that crisscross the floor of Philolaus Crater. Lunar sinuous rilles are generally thought to be collapsed, or partially collapsed, lava tubes, underground tunnels that were once streams of flowing lava.

“The highest resolution images available for Philolaus Crater do not allow the pits to be identified as lava tube skylights with 100 percent certainty, but we are looking at good candidates considering simultaneously their size, shape, lighting conditions and geologic setting” says Pascal Lee, planetary scientist at the SETI Institute and the Mars Institute who made the new finding at NASA’s Ames Research Center in Silicon Valley.

…Prior to this discovery, over 200 pits had been found on the Moon by other researchers, with many identified as likely skylights leading to underground lava tubes associated with similar sinuous rilles. However, today’s announcement represents the first published report of possible lava tube skylights in the Moon’s polar regions.

The floor of the crater as a lot of rilles, and a close look at that crater floor reveals to me a lot of possible sky light entrances, more than indicated by the images at the llink. (Go here, click on projections and pick “Orthographic (North Pole).” Then zoom in on the crater indicated by the yellow X in my image on the right above.)

The key here is that caves or lava tubes provide a good place to cheaply and quickly establish a lunar colony. While it is suspected that water might survive in permanently shadowed regions near the poles, up until now no one had found any good underground locations there. If this suspected skylight entrances prove true, this crater then becomes prime real estate on the Moon.



  • Tom Billings

    This is outstanding news! The closer to the poles, the better the chance of an ice cave. What is now needed is an orbiting ground-penetrating radar, to detect and characterize the size of lava tubes on the Moon, in lunar polar orbit. A multi-bandwidth radar might do better at distinguishing ice inside a cave, given the lower electrical contrast between ice and rock than between water and rock.

    When I talked with Dr. Brown ( who ran the Apollo Lunar Sounder experiment on Apollo 17) about such an orbiter in 1990 he said it would cost a billion dollars for such a mission. Today, that is no longer the case, and the price is dropping. The Sood, Melosh, Howell proposal of a year ago (https://www.researchgate.net/publication/298529224) is the latest I’ve seen for such a probe of the Moon.

    In spite of the recent political interest in lunar work, I would far rather see such a mission done privately, to avoid the academic/political complications of NASA’s projects. That is not yet probable, but is becoming increasingly possible as new companies announce their focus on lunar development yearly.

  • wodun

    It is tough to tell what might be there and what is just shadows. While Tom Billings has a very rational and knowledgeable suggestion above, it would also be nice to be able to just send some people over to check things out. One day!

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