Groundbreaking Discoveries: Chang’e-6 Unveils Recent Volcanic Activity on the Moon’s Far Side

The first soil samples from the far side of the moon show signs of dramatic volcanic activity near the moon’s south pole. Two separate studies of lunar rocks taken by China’s Chang’e-6 spacecraft show that the rocks formed from magma cooling relatively recently, about 2.8 billion years ago. , according to papers published on November 15, 2024 in Science and Nature. The measurements could help solve the mystery of why the far side of the moon is so different from the far side, but also raise new questions about the history of volcanism on the moon.

The two sides of the moon are like night and day, with different topography, chemical composition, crater density and evidence for volcanism. Large solid lava pools called mare cover nearly a third of the short side. But only about 2 percent of the back shows signs of lava flows. “The remarkable asymmetry between the front and back of the Moon … is a long-standing, unsolved puzzle,” geochemist Qiu-Li Li of the Chinese Academy of Sciences in Beijing and co -works writing in Nature. Until recently, all the rocks brought back from the moon came from the nearby side. Samples from the Apollo and Luna missions in the 1960s and 1970s suggested that the more volcanically active moon about 4 billion years ago and that it had largely cooled about 3 billion years ago.Rocks from the Chang’e-5 mission in China showed more recent volcanism, about 2 billion years ago back. But the volcanic history of the West was a complete mystery until China’s Chang’e-6 mission returned the first soil samples ever collected from the region Earth with nearly two kilograms of lunar rocks from the South Pole-Aitken Basin, the oldest and largest crater and source of most of the volcanic material on the far side of the moon.

“Imagine you have rock samples from maybe 10 places in North America, and that’s all you know about Earth,” said planetary scientist Stephen Elardo of the University of Florida in Gainesville, who was not involved in the work. new. “Then all of a sudden you get your first stones from South Africa or Australia. Now you get that as another data point to learn about the whole planet. That’s basically what this is for the moon.” Two groups examined the rocks using radiometric data, a technique for estimating an object’s age based on the relative amounts of certain radioactive elements it contains. The geochemist Le Zhang from the Chinese Academy of Sciences in Guangzhou and colleagues studied 35 pieces of volcanic rock called basalt and found that their age was about 2.830 billion years, the researchers said in Science. Li and colleagues examined 108 pieces of basalt and found a similar age: 2.807 billion years, the team reports in Nature.

“That’s much younger than I expected for that region of the moon,” Elardo says. This is due to another feature that both groups found in the soil samples. The rocks lack heat elements such as potassium, rare earth elements (such as uranium and thorium) and phosphorus, collectively known as KREEP. Alternatively, KREEP’s decaying elements could have kept the Moon’s mantle warm enough to sustain volcanism until 2 billion years ago. But without these elements, it is not clear how the back could have been melted for so long, Elardo says. The results also indicate long-term volcanism. Li’s team found one rock in particular that stood out: an aluminum-rich fragment dating back to 4.2 billion years ago. The only known lunar rock that is older is a meteorite, which does not know where the moon came from. Together with the younger samples, the rocks show that volcanism on the far side of the moon lasted at least 1.4 billion years.

Given the known differences between the moon’s hemispheres, it’s not surprising that the first soil samples from the far side look so different from those from the front, says sample keeper Ryan Zeigler Apollo ground at the Johnson Space Center in Houston. But the data is still encouraging. “I think this is just step one,” Zeigler says. “I think with more time they will spread more ways to these grains. And I think there will be more amazing things to come.”

Source: Science News