What's so hot? Two moon craters are hiding an ancient volcano that last erupted 3.5 billion years ago

Scientists have found a mass under two craters of the Moon emitting heat, hinting at the presence of an object that is very rare outside of Earth. Volcanism has been identified on the lunar surface, with lava fields and eruptions common billions of years ago. However, these volcanoes were different from the ones found on Earth. But then one such was identified, with signs present beneath the Compton and Belkovich craters on the far side of the Moon. The object found on the Moon is granite, hardly ever found anywhere else but on Earth. The process of its formation involves a volcano where magma can cool down and crystallise, besides water and tectonics.

To see what lay beneath these craters and was emitting heat, the researchers used data from Chinese and American lunar orbiters. This led them to a volcanic process never seen before on the Moon, IFL Science reported. Co-lead researcher, Dr Matt Siegler, of the Planetary Science Institute, said in a statement, that an instrument on both the Chinese Chang'E 1 and 2 orbiters helped the team map temperatures below the surface. “What this means is that it is hot, not necessarily at the surface, as you would see in infrared, but under the surface," he added. This means that there is extra heat coming from somewhere below the feature within the deeper lunar crust. "So Compton-Belkovich, thought to be a volcano, is also hiding a large heat source below it," Matt said.

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Warmer surface exposed a volcanic area

This volcanic surface spans 20 kilometres, is rich in silicon and is believed to be the caldera of this ancient volcano. The last eruption supposedly happened 3.5 billion years ago, yet this portion is 10 degrees Celsius warmer than the nearby areas. Scientists think this heat is from radioactive elements that got stuck in the rocks. "We interpret this heat flux as resulting from a radiogenic-rich granite body below the caldera," Dr Siegler said.

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His wife, Dr Rita Economos, a geochemist, explained that what they have found is a "50km wide batholith". It is a "type of volcanic rock that forms when lava rises into the earth's crust but does not erupt onto the surface." This discovery of granite in one region on the Moon opens the possibility of finding it in other lunar areas, and even on more cosmic bodies.