December 9, 2023

Using microwave instruments to probe deep beneath the surface of the moon’s far side, researchers have discovered a “hot spot” that they describe as a massive block of subsurface granite, suggesting the moon is more “Earth-like” than we thought.

Granite is common on Earth due to the planet’s abundance of water and tectonic plates, which help melt and recycle materials from the Earth’s crust. They are virtually absent elsewhere in the solar system, though. But now, a new study has made an unexpected discovery: a massive granite block on the far side of the moon.

The discovery was made using microwave instruments on China’s unmanned lunar spacecraft Chang’e-1 and Chang’e-2. The researchers supplemented the data from NASA’s Lunar Reconnaissance Orbiter (LRO) with older information collected from the Lunar Prospector, Gravity Recovery and Interior Laboratory (GRAIL), Chandrayaan 1, and Apollo missions. collected data.

“Using instruments at microwave wavelengths (longer than infrared) sent to the moon by China’s Chang’e-1 and 2 orbiters, we have been able to map the temperature below the surface,” said Matthew Sigler, lead author of the study. Siegler) said.

Because of the longer wavelength, microwave radiometry allows scientists to look deeper below the surface, measuring the physical temperature of the subsurface at about 1 foot to 18 feet (0.3 m to 5.6 m). Researchers have discovered a topographically unexplained “hot spot” between the ancient Compton and Berkovich craters on the moon’s mysterious far side. The only plausible explanation they could think of was that it was an enhanced underground geothermal source.

“We found extra heat at a location on the moon that was thought to be a long-dead volcano that last erupted 3.5 billion years ago,” Sigler said. “It was about 50 kilometers in diameter. (164 feet), the only solution we can think of to generate so much heat is a large block of granite, a type of rock that forms when the magma body (unexploded lava) beneath the volcano cools. Unlike the rest of the Moon’s crust Compared to other rocks, granite contains high concentrations of radioactive elements such as uranium and thorium, which lead to the heat we can feel on the surface of the moon.”

Arrows in (b) show the location of large granite blocks on the lunar far side.  (a) and (c) show the thermal gradient in granite between the Berkovich and Compton craters.
Arrows in (b) show the location of large granite blocks on the lunar far side. Images (a) and (c) show the thermal gradient in granite between the Berkovich and Compton craters.

Matthew Siegler/PSI

The researchers concluded that the large volcano was once powered by a larger granite magma chamber beneath it. The Apollo missions brought back small samples of granite material from the Moon, but not on this scale. The size of the feature suggests the moon is more like our planet than previously thought, the researchers said.

“It’s more Earth-like than we thought it would have been created on the Moon, which lacks the water and plate tectonics that help form granite on Earth,” Sigler said. “It also shows that remote sensing can pick up hidden features, which will lead to Helps to explore other planetary bodies in the solar system.”

Researchers will present their findings at the meeting Goldschmidt Conference The study appears in the journal Lyon, France, on July 12, 2023 nature.

source: Planetary Science Institute, Urik Alert!