China’s first lunar rock ignites a research boom


Scientists in China have had the opportunity to analyze moon rocks for the first time.Credit: Ren Hui/VCG/Getty

Until recently, chronological geologist Li Xian-Hua’s research focused on molten rocks on Earth. But when a Chinese spacecraft delivered the country’s first moon rocks in December 2020, Li focused on studying them. “I’m a new person working on extraterrestrial rocks,” says Li, who works at the Institute of Geology and Geophysics (IGG) at the Chinese Academy of Sciences in Beijing.

Li is one of several planetary scientists in China who have had the opportunity to study lunar rocks for the first time. The samples, collected by the Chang’e-5 spacecraft, are the first to have been returned to Earth since the NASA and Luna missions of the Soviet Union more than 40 years ago. They are examined to gain insight into the evolution of the moon.

These studies are beginning to yield exciting results. About six research papers on Chang’e-5 samples have been published in the past six months. And last week, at the Planetary and Lunar Science Conference in Houston, Texas, a session on Chinese missions to the moon featured nearly a dozen studies.

“There are a lot of young Chinese researchers involved,” says Clive Neal, a geologist at the University of Notre Dame in Indiana who worked on the Chang’e-5 samples with collaborators in China. Several researchers and postgraduate students presented work on lunar samples at the conference in Houston, he says. The rocks are exciting because they “represent a window into a completely different era of lunar magma” compared to those collected earlier, says Neal.

smallest rocks

The Chang’e-5 mission recovered 1.7 kilograms of loose volcanic material called basalt from a vast lava plain, known as Oceanus Procellarum, in the northern region of the Moon. The site was chosen in part because it may contain newer volcanic material from the areas visited by the Luna and Apollo missions. The hope was that a younger site would provide insight into when the moon began to cool but was still volcanically active.

Last July, the China National Space Administration released the first samples to scientists across China. Approximately 17.5 grams of fine-grained, hard-rock powder were distributed to 31 science projects selected from 85 applications. This was followed by several more rounds of applications for working with lunar samples.

The first teams scrambled to date the moon rocks. On October 7, one team reported an age of 1.96 billion years (more or less 57 million years) for basalt1. Less than two weeks later, another team, including Lee, corroborated those dates, estimating the age at 2 billion years (more or less 4 million years)2.

The results confirmed that the Moon was still volcanically active nearly a billion years after the Apollo rocks suggested that activity peaked. But determining why this activity is fueling has turned out to be difficult.

One leading theory, based on satellite observations, suggested that heat-producing radioactive elements such as potassium and thorium found in the lunar mantle may have driven the volcanoes. But when another team at IGG examined lunar basalt, they determined that the high levels of these elements3 You are not the source.

Another possibility was that the mantle contained enough water to reduce the temperature at which materials melt and facilitate the eruption of magma. But Lin Yangting, a planetary scientist at the IGG, and colleagues found that the lunar rocks may have come from a relatively dry source.4.

Confounded

The question of the source of the volcano’s heat has stunned scientists. “I don’t have an answer for this,” says Lane, who has previously studied meteorites on Earth.

“This is a very big scientific problem, because it reveals how much we still have to learn about the evolution of the moon,” says Weibiao Hsu, a planetary geochemist at the Purple Mountain Observatory, CAS, in Nanjing, China.

Hsu, who obtained two slices of basalt, wonders if a closer look at these basalts might reveal that they actually come from a rich source of heat-producing elements, because the recently published study by Lin and colleagues was conducted on soil samples that contain many materials. Hsu found that the rocks contained high levels of titanium, indicating that it came from deep in the mantle.

“We are exploring all possibilities,” says Ming Tang, a geochemist at Peking University in Beijing, who has received two tiny basalt rocks and will analyze them to better understand the pressure and temperature at which they formed. These samples are the first of their kind for Tang, who had previously studied magma from volcanoes on Earth. “It’s a good opportunity for me and many other Chinese scientists interested in expanding their field,” Tang says.

At the moment, theories abound about the source of the moon’s heat. But Hsu says there will be plenty of groups trying to solve the mystery and gain other insights into the moon. He’s seen many researchers join the field since the Chang’e-5 samples arrived. This year, his lab has received more applications from students eager to join a graduate program than they can accommodate. “This has never been the case before.”

Lin expects more researchers to participate. Within the next decade, China is planning a mission return to the south pole of the Moon and another to Mars.

“Twenty to thirty years ago, this was just a dream. It’s now a reality,” he tells me.

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