A big 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 results of cooling magma that fed fiery eruptions of lunar volcanoes around 3.5 billion years ago.
Finding the stays of volcanic activity on this region of the moon is not 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, nonetheless, is just how large this patch of cooled magma is, with an estimated width of around 31 miles (50 kilometers). The invention of this massive body of granite beneath the Compton-Belkovich volcanic complex could help scientists explain how the lunar crust formed within the moon’s early history.
Related: Space volcanoes: Origins, variants and eruptions
The invention 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 info produced by the orbiter allowed the team to measure temperatures below the surface of Compton-Belkovich. The info showed heat being generated that might only come from radioactive elements that only exist on the moon as granite — an igneous rock present in the “plumbing” of volcanoes as “batholith,” underground rock formations created when magma cools without erupting.
“Any big body of granite that we discover on Earth used to feed an enormous bunch of volcanoes, very similar to a big system is feeding the Cascade volcanoes within the Pacific Northwest today,” Siegler said in a press release. “Batholiths are much greater than the volcanoes they feed on the surface. For instance, the Sierra Nevada mountains are a batholith, left from a volcanic chain within the western United States that existed way back.”
The formation of granite on Earth is frequently the results 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 in consequence of the absence of each water and plate tectonics. Meaning this discovery could point toward the conditions locally or globally found on the moon when it was host to volcanic activity.
‘If you happen to haven’t got water, it takes extreme situations to make granite,’ Siegler said. “So, here’s this method with no water and no plate tectonics — but you will have granite. Was there water on the moon — at the very least on this one spot? Or was it just especially hot?”
Siegler will present the team’s research on 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 within the journal Nature.