Formation of granite uncovered beneath an ancient lunar volcano

Evidence of a large granite formation beneath the ancient lunar volcano called Compton-Belkovich has provided further support for the theory that the far side of the moon experienced volcanic activity in the past.

Geologists have discovered granite beneath the suspected volcanic feature on the moon’s surface, which is believed to have formed as a result of cooling magma from lunar volcanoes approximately 3.5 billion years ago.

For a long time, researchers have suspected that this area could be an ancient complex of volcanoes. However, the size of the cooled magma patch beneath Compton-Belkovich, estimated to be about 31 miles (50 kilometers) wide, surprised the team.

This unexpected finding of a large body of granite beneath the Compton-Belkovich volcanic complex has the potential to provide insights into the early formation of the lunar crust.

Led by Matthew Siegler of the Planetary Science Institute, a team of scientists made the discovery using data collected by NASA’s Lunar Reconnaissance Orbiter.

The data obtained from the orbiter allowed the team to measure temperatures beneath the surface of Compton-Belkovich, which revealed the presence of heat generated by radioactive elements unique to the moon and associated with granite.

Siegler explained that on Earth, large bodies of granite are typically associated with volcanic systems, similar to how the Cascade volcanoes are fed by a large system in the Pacific Northwest. Batholiths, which are underground rock formations created when magma cools without erupting, are larger than the volcanoes they feed on the surface.

The rarity of granites on the moon makes their discovery significant in understanding the formation of the lunar crust. Granites on Earth are usually formed through the involvement of water and plate tectonics, but the moon lacks these factors. Siegler raised the question of whether water was present in that specific spot on the moon or if other extreme conditions led to the formation of granite.

Siegler and his team will present their research at the upcoming Goldschmidt Conference in Lyon, France, from July 9-14.