Lunar scientists have announced the discovery of a 50-kilometer-wide piece of rock beneath the surface of the lunar sides and is made of something commonly found in kitchens.
The team detailed their startling discovery on Thursday, days before presenting the work at the Goldschmidt geochemistry conference in Lyon, France. A series of satellites has detected a heat source near the site of an ancient lunar caldera, a depression formed when magma empties from a collapsing volcanic chamber. Satellites noted that this spot was about 10 degrees Celsius hotter than its surroundings. They suspect it comes from a giant slab of granite.
We discovered extra heat escaping from the ground at a location on the moon thought to be a long-dead volcano that last erupted over 3.5 billion years ago, said Matt Siegler, lead researcher and senior scientist at Planetary Science. Institute in Arizona. in Thursday’s announcement. A paper detailing the work was published in the journal Wednesday Nature.
This diagram shows the location of the granite on the far side of the Moon. On the left, the arrow indicates the position of the large piece of granite, called a basolith, in an overall view of the Moon. In the center, a box shows the location and thermal gradient of the granite on a map of the lunar surface. At right, a side view shows the heat gradient.
Siegler et al, Nature, July 2023
It is about 50 km in diameter, and the only solution we can think of that produces that much heat is a large body of granite, a rock that forms when a body of magma, the unerupted lava under a volcano, cools, he added.
Why is there granite on the moon?
According to the announcement, granite is almost absent in the Solar System except on Earth, and only small grains of granite have been found in rock samples from the Apollo Moon.
On Earth, granite forms when water interacts with tectonic plates in the crust. According to the National Park Service, granite rocks are found on continents around the world near active or past plate boundaries. Granite forms when magma rises close to the surface, but does not erupt, and then slowly cools underground. Granite can become visible on the surface when the volcanic rock on top erodes over time. Yosemite National Parks El Capitan and Half Dome are good examples of granite slabs. Their enormous size earns them the title of batholith.
But the Moon has no water or plate tectonics in the traditional sense. However, it has undergone some volcanism and has pockets of water ice near its poles. Whether granite exists on the moon is still a little puzzled. This is more Earth-like than we had imagined could be produced on the Moon, which lacks the water and plate tectonics that help granite form on Earth, Siegler said.
A view of El Capitan as snow blanketed California’s Yosemite National Park on February 22, 2023.
Anadolu Agency/Anadolu Agency/Getty Images
Siegler goes on to thank his wife Rita Economos, a geochemist and associate professor at Southern Methodist University in Texas, pointing out that despite the lunar position, the spacecraft’s observations were picking out the granite.
To tell the truth, we were a little perplexed when we found it: luckily my wife, Dr. Rita Economos, is the family geochemist, so with her guidance we were able to reconstruct the probable geological cause of the thermal anomaly, he said Siegler.
Explore the Solar System
The new work came about thanks to the surveying capabilities of four lunar spacecraft: China’s Change 1 and 2 lunar orbiters, NASA’s Lunar Prospector and its Lunar Reconnaissance Orbiter. The work shows that remote sensing can detect features hidden beneath the surface of extraterrestrial terrain, Siegler says.
This will be useful in exploring other planetary bodies in the Solar System, he adds.
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