Huge granite 'body' on far side of the moon offers clues to ancient lunar volcanoes

a photograph of the moon's far side as seen from space
This image of the moon was obtained in 1996 as NASA's Galileo spacecraft passed the Earth and was able to view the lunar surface from a vantage point not possible from the Earth. (Image credit: NASA/JPL)

A large formation of granite discovered beneath an ancient lunar volcano is further evidence that the far side of the moon once glowed with volcanic eruptions.

The granite was found under a suspected volcanic feature on the surface of the moon called Compton-Belkovich. This feature was likely formed as the result of cooling magma that fed fiery eruptions of lunar volcanoes around 3.5 billion years ago. 

Finding the remains of volcanic activity in this region of the moon isn't completely unexpected, as researchers have long suspected this area to be an ancient complex of volcanoes. What has come as a surprise to the team, however, is just how large this patch of cooled magma is, with an estimated width of around 31 miles (50 kilometers). The discovery of this large body of granite beneath the Compton-Belkovich volcanic complex could help scientists explain how the lunar crust formed in the moon's early history.

Related: Space volcanoes: Origins, variants and eruptions

The discovery of the granite body was made by a team of scientists led by Planetary Science Institute researcher Matthew Siegler using data collected by NASA's Lunar Reconnaissance Orbiter. The data produced by the orbiter allowed the team to measure temperatures below the surface of Compton-Belkovich. The data showed heat being generated that could only come from radioactive elements that only exist on the moon as granite  —  an igneous rock found in the "plumbing" of volcanoes as "batholith," underground rock formations created when magma cools without erupting.

Microwave data shows heat below a volcanic feature on the moon called Compton-Belkovich. (Image credit: NASA/Nature/Robert Lea)

"Any big body of granite that we find on Earth used to feed a big bunch of volcanoes, much like a large system is feeding the Cascade volcanoes in the Pacific Northwest today," Siegler said in a statement. "Batholiths are much bigger than the volcanoes they feed on the surface. For example, the Sierra Nevada mountains are a batholith, left from a volcanic chain in the western United States that existed long ago."

The formation of granite on Earth is usually the result of water and plate tectonics creating large areas of melted rock called melt bodies beneath our planet's surface. Though common on Earth, granites are much scarcer on the moon as a result of the absence of both water and plate tectonics. That means this discovery could point toward the conditions locally or globally found on the moon when it was host to volcanic activity.

'If you don't have water, it takes extreme situations to make granite,' Siegler said. "So, here's this system with no water and no plate tectonics  —  but you have granite. Was there water on the moon  —  at least in this one spot? Or was it just especially hot?"

Siegler will present the team's research at the Goldschmidt Conference, in Lyon, France, between July 9 and 14. The team's findings are also discussed in a paper published on July 5 in the journal Nature.

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Robert Lea
Senior Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

  • Broadlands
    " This feature was likely formed as the result of cooling magma that fed fiery eruptions of lunar volcanoes around 3.5 billion years ago. "

    There should be large amounts of coarse-grained pyroclastic rocks in the vicinity of these old volcanoes as there was no running water to erode them. These should be seen from space. Have they looked?
  • A. Wolfe
    Yes, please see:

    Explosive Volcanism Associated With the Silicic Compton-Belkovich Volcanic Complex:: Implications for Magma Water Content
  • Broadlands
    I was thinking more about these kinds of evidence...
    Larger fragments seen from space.
  • rod
    Looks like lunar catastrophism operating when life flourished during the Precambrian on Earth.

    Meteorites and volcanoes may have helped jump-start life on Earth,
    The story of abiogenesis on Earth continues to become more interesting I feel, as more and more catastrophism shows up for the early Earth and Moon.
  • Broadlands
    To "jump start" life anywhere there must be liquid water and protection from solar UV radiation . But also dry land for abiogenesis to form peptide and nucleotide bonds leading to DNA and proteins. Meteorites could provide the starting materials...amino acids. Liquid water the source of oxygen for ozone in the stratosphere. Hydrogen escaping to space.
  • rod
    Just my thinking here. The reports coming out now about so much violent catastrophism for the early Earth and Moon system, abiogenesis must avoid being destroyed at the start, and then taking place again, again, and again. I considered this after reading Charles Darwin letters on the warm little pond from 1871 and 1882.
    My note Charles Darwin hoped that someday evidence would be shown for life evolving from non-living matter but in his time, none was known that was *worth anything* and the *law of continuity* would provide this, also a general law of nature for abiogenesis. None of this in science is proven at present. There is no general law of abiogenesis seen operating in nature. So, here is a summary of four points in these letters that I learned.

    1. A warm little pond is postulated for the origin of life on Earth but Charles Darwin thought if abiogenesis operating in a warm little pond in his time, perhaps such life evolving from non-living matter would be quickly destroyed by existing life and eaten.

    2. No good evidence for abiogenesis taking place in Charles Darwin time seen in nature.

    3. The law of continuity is needed for abiogenesis to work apparently, and

    4. Someday a general law of nature developed to describe and show abiogenesis like other laws of nature, for example the laws of motion or law of gravity. Apparently all four I list here are missing in science today, even with natural law operating in nature in a uniform manner, i.e., *law of continuity*. When I consider point #1, it is good IMO to avoid catastrophism that wipes out abiogenesis creating life from non-living matter at the very beginning otherwise many abiogenesis events must be envisioned to replace the earlier efforts that failed. These are four points I learned by reading some of Charles Darwin letters on the warm little pond and origin of life on Earth and comparing to all the catastrophism documented now for the early Earth-Moon system.
  • Pogo
    The lunar Uluru (Ayers Rock)! Except that it’s granite, not sandstone.
  • Harry Costas
    Interesting thank you.