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Scientists have discovered an anomalous formation of radioactive granite that has been slowly releasing heat below the surface in a crater on the far side of the Moon.. This unexpected find could provide valuable clues about the history of our natural satellite.
Although it seems taken from a science fiction work, it is about ancient volcanism. It has long been known that the Moon had lava fields and eruptions in its past, but no evidence of a more conventional volcano, similar to those on Earth, has ever been found. However, astronomers have looked at what lies beneath the Compton-Belkovich craters and have come to a startling conclusion.
According to a new study published in the journal Nature earlier this month, A volcano that has been inactive for approximately 3.5 billion years is believed to be the source of this unusual chunk of granite.
ancient lunar volcanoes
“It is more Earth-like than we had imagined it could be on the Moon, which lacks the water and tectonic plates that help granites form on Earth,” the study’s lead author said in a statement. Matt Siegler of the Planetary Science Institute in Tucson, Arizona.
In his article, the researchers argue that the existence of granite below the surface suggests that the far side of the Moon, which has been less explored and has always remained opposite to Earth, hosted in its early past one or several volcanoes that erupted approximately 3.5 billion years ago.
“Any large mass of granite that we found on Earth used to feed a large group of volcanoes,” Siegler said.
Siegler and his colleague Rita Economos of Southern Methodist University discovered the heat with a new method that uses microwaves to measure ground temperatures via China’s Chang’E 1 and 2 lunar orbiters. They also used data from NASA’s Lunar Prospector and Lunar Reconnaissance orbiters.
“What we discovered was that one of these putative volcanoes, known as Compton-Belkovich, it was absolutely brilliant at microwave wavelengths,” Siegler said. “What this means is that it is hot, not necessarily on the surface, as you would see in the infrared, but just below the surface. The only way to explain this is that the extra heat comes from somewhere beneath the object, in the deeper lunar crust. So Compton-Belkovich, which is believed to be a volcano, also hides a large heat source underneath,” he added.
Radioactivity of the elements attached to the rocks
The data reveals the presence of an extensive silicon-rich area approximately 20 kilometers wide., which researchers identify as the caldera of the ancient volcano. This region shows a temperature that is 10 °C higher than its surrounding environment. However, this thermal disparity, according to the researchers, is not due to the presence of magma below the surface, but to the radioactivity of the elements attached to the rocks.
“We interpret this heat flow as coming from a radiogenic-rich granite body located under the caldera,” explains Siegler. “Honestly, we were a bit stumped when we found it: luckily, my wife, Dr. Rita Economos, is the family geochemist, so with her guidance, we were able to piece together the probable geological cause of the thermal anomaly. ”, he added.
Economos offers an explanation for this discovery, highlighting the presence of a batholith with a width of 50 km. Batholiths, he explains, are volcanic rock formations that are generated when lava rises in the earth’s crust but does not erupt on the surface. Known examples of similar granite boulders rising to the surface can be found at El Capitan and Half Dome in Yosemite, California.
Despite the fascinating findings, Scientists face a landscape with more questions than answers.
“If there is no water, extreme situations are needed to produce granite,” explains Siegler. “So here we have a system without water and without plate tectonics, but with granite. Was there water on the Moon, at least in this place? Or was it just too hot?
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