Radioactive slab discovered under the Moon's surface that emits heat: what is it?
A large mass of granite, which is radioactive and slowly releases heat, has been discovered on the back of the Moon near the Compton and Belkovich craters. Scientists believe that this discovery confirms the theory that the side of the satellite facing away from the Earth once had active volcanoes.
This is stated in a study published in the scientific journal Nature. Scientists suggest that the granite formation was probably formed as a result of the cooling of magma that powered fiery eruptions of lunar volcanoes about 3.5 billion years ago.
Granite is not very common outside of Earth, so scientists were somewhat surprised to find it on the Moon. On our planet, it usually appears deep beneath volcanoes, where magma cools and crystallises. In fact, it is the result of water and plate tectonics, which create large areas of molten rock below the planet's surface.
"If you don't have water, you need extreme situations to form granite. So, here is this system without water and without plate tectonics - but you have granite. Was there water on the Moon - at least in this place? Or was it just too hot?" - said study co-leader Dr Matt Sigler of the Planetary Science Institute.
The discovery on the Moon was made by combining data from Chinese and American lunar orbiters.
"Using an instrument that operates in the microwave range (which is longer than infrared), we were able to map the temperatures beneath the lunar surface. We found that one of the probable volcanoes, known as Compton Belkovich, was absolutely glowing in the microwave range," Sigler said.
The scientist explained that the data obtained indicate that this place is hot and the heat source is not necessarily close to the surface.
"The only way to explain this is additional heat coming from somewhere deep in the lunar crust. So Compton Belkovich, which is considered a volcano, is also hiding a large heat source," he said.
According to the data, the silicon-rich 20-kilometre surface area is likely to be a caldera, a cirque-like depression formed by the collapse of the ancient volcano's summit. The temperature there is 10°C higher than around it. But the reason for this heat is not hot magma, as the volcano last erupted 3.5 billion years ago, but radioactive elements trapped in the rocks.
Sigler explained that the researchers believe the heat flow "comes from a granite body rich in radiogenic elements located beneath the caldera".
He also admitted that his wife, Rita Economos, who is a geochemist, helped him to unravel the cause of the thermal anomaly.
The presence of such a large deposit of granite in a place where you wouldn't expect it suggests that there may be other areas on the Moon where granite can be found. Perhaps the same applies to other places in the solar system.
Earlier, OBOZREVATEL also reported that life could exist on the Moon.