Kaguya Discovers a Lava Tube on the Moon

Article written: 25 Nov , 2009
Updated: 24 Dec , 2015


Future lunar astronauts may want to brush up on their spelunking skills: the first lava tube has been discovered on the moon.

In a recent paper published in Geophysical Research Letters, Junichi Haruyama and colleagues report that they have discovered a mysterious hole in the lunar surface in high resolution images from the Kaguya spacecraft. The hole is 65 meters in diameter and is located in the volcanic Marius Hills region on the near side of the moon, right in the middle of a long sinuous rille. Sinuous rilles are thought to be formed by flowing lava, either on the surface or in enclosed lava tubes.

Of course, there are a lot of ways to form a hole in the surface of the moon. The most obvious is with an impact: the moon has literally been battered to pieces over the years by rocks from space. Couldn’t this hole be a fresh impact crater? Nope. Haruyama’s team observed the hole nine separate times, at various illumination angles, and even when the sun was almost directly overhead it looked mostly black, suggesting that it is very deep. They calculate a depth of around 88 meters, so the hole is deeper than it is wide. No impact crater is like that.

Four different views of the lava tube skylight at varying sun angles. Arrows indicate the direction of incident sunlight (I) and the viewing direction (V). Image credit: JAXA/SELENE

Four different views of the lava tube skylight at varying sun angles. Arrows indicate the direction of incident sunlight (I) and the viewing direction (V). Image credit: JAXA/SELENE

Another possibility is that the hole is due to some sort of volcanic eruption, but there is no sign of volcanic deposits like lava flows or ash emanating from the hole. The hole is isolated, so it isn’t likely to be due to a fracture in the lunar crust either – you would expect such a fracture to form a chain of holes.

Haruyama’s team concluded that the most likely explanation is that the hole that they discovered is a “skylight” – a location where the roof of a lava tube collapsed, either when the lava filling the tube flowed away, or later in the moon’s history due to an impact, moonquake, or tidal forces from the Earth. If it is a lava tube, their calculations based on the multiple images of the hole show that the tube could be 370 meters across.

Lava tubes are important in understanding how lava was transported on the early moon, but they are not just a scientific curiosity: they may also provide valuable refuges for future human explorers. The surface of the moon is not protected from the harsh radiation of space by a magnetic field or a thick atmosphere, so a long term human presence would be most feasible if astronauts could spend most of their time shielded underground. Digging a hole large enough to fit an entire moon colony in it would be a huge engineering challenge, but lava tubes could provide ready-made locations for a well-shielded base, making future astronauts the most technologically advanced cave-dwellers in history.

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12 Responses

  1. J. Major says

    They better clear out all the horta eggs first.

  2. Member
    Aqua says

    No apparent mountain ranges nearby? Fairly smooth terrain on the approach?

    I see a Thanksgiving Dinner being served in a classy hotel inside a volcanic tube on the Moon. Puts a whole new spin on the concept of accompanying the meal with ‘sparkling wines’ or other carbonated beverages? Interesting 1/6 G bubbles anyway.. takes fewer to ‘get you there’?

    Prosit! And Happy Thanksgiving! USA!

  3. Member
    Aqua says

    And special thanks to the Kaguya team! Domo origato.. Hai!

  4. Savino says

    The same already was found on mars, if I not wrong.
    Probably we can find others lava-tubes in the outer-solar system bodies, like Ganimedes or Io (not that someone would like to stay some hours in a old sulfur-lava-tube on Io)

  5. Jon Hanford says

    Sounds like an invitation for a 21st century update of Welles’ “The First Men In The Moon” 🙂

  6. geokstr says

    Sorry to waylay this thread, but there seems no other way to contact Nancy Atkinson, the local pro-AGW alarmism advocate on this site. I was just wondering why she has not posted anything about THE CRU data dump that appears to show where exactly this “consensus” the alarmists have been bragging about comes from. Namely, an orchestrated conspiracy to prevent any anti-AGW research from passing the so-called “peer review” process by excluding them without bothering to review them at all. Plus the strong inferences that data has been “massaged” to give the correct results, and other data subject to Freedom of Information laws that they claimed has been “lost” has actually been deliberately deleted.

    Perhaps she, like the major “so-called” media, is either waiting for the official talking points to be developed, or are holding her hands over her ears while shouting “NA NA NA, I CAN’T HEAR YOU.”

  7. Nexus says

    they have indeed found similar caves on Mars. Exciting stuff.

    I think this tube on the Moon would be a good place to look for water. As I understand it, one of the things that tends to destroy water on the Moon is photodissociation by sunlight- but since the cave is so dark and deep that is not going to be as much of a problem.

  8. Nexus says


    what on Earth does stupid anti-science denialism have to do with caves on the moon?

  9. Member
    Jon says

    Heh, let’s talk first about the geological stability of that tube before getting ahead of ourselves here. Although, less gravity = less chance you could get crushed by moon rubble?

  10. Dominion says

    The moon IS made of cheese! And apparently it is Swiss…

  11. Dave Finton says

    Has anyone mentioned that “Moon Tubes” would be a great name for a band?

  12. gypkap says

    Just so you know, the geological study of caves (on Earth or on the Moon or Mars) is called speleology. Cave scientists are called speleologists, and amateurs are called cavers. The term “spelunker” was abandoned sometime in the late 1950s.

    That said, the lava tube entrance that was found on the Moon is impressive. There are skylights in many lava tubes on Earth. Existing lava tubes are a feasible place to build the first dwellings on the Moon, and maybe Mars.

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