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China’s rock samples brought back from the moon shed light on meteor strikes here on Earth, say scientists

Tan KW
Publish date: Sat, 01 Oct 2022, 12:13 PM
Tiny lunar glass beads that form after asteroid strikes reveal how meteorite impacts on the moon million years ago mirrored those on Earth, including the celestial crash that doomed the dinosaurs, say scientists.
After analysing lunar soil samples brought back by China’s Chang’e 5 mission in late 2020, the international research team said the moon could be used as a blueprint to construct a timeline showing the bombardment of Earth.
“The moon is the Earth’s natural satellite. Think about the Earth and moon being one system,” said co-author Katarina Miljkovic, an associate professor at the Space Science and Technology Centre at Curtin University in Australia. 
“If there was an asteroid break-up or something that would send a flurry of impacts over time, there is no reason to believe that if some of them hit the moon, the Earth was spared entirely,” the planetary scientist said.
The international team of 23 scientists from institutes in Australia, Britain, China, Sweden and the United States analysed 215 glass beads with a diameter over 50 micrometres, similar to the size of human hair.
The beads were selected under the microscope from 2 grams (0.07oz) of Chang’e 5 lunar regolith - loose rock and dust - allocated by the China National Space Administration and analysed by experts using microscopic analytical techniques, numerical modelling and geological surveys.
“The data ... give an initial indication that lunar glass populations may provide a proxy for changing impact rates in the inner solar system and possible relationships to dynamical processes in the asteroid belt,” the team wrote in an article published in the peer-reviewed journal Science Advances on Thursday.
The Chang’e 5 probe returned in December 2020 with the first moon samples taken in 44 years, making China the third country to bring lunar rocks and dust back after the United States and the Soviet Union.
The mission brought back 1.7kg (3.74lbs) of rocks and dust from Oceanus Procellarum, or the Ocean of Storms. The rocks there, formed about 2 billion years ago, are the youngest lunar samples ever analysed in contrast to the samples collected during the American Apollo and Soviet Luna missions which were found to be more than 3 billion years old.
Miljkovic said impact glass beads were a common feature on the moon and Earth created by the heat and pressure of meteorite impacts, but they were hard to come by on Earth.
“Our planet is quite dynamic so they are quite difficult to find on Earth. We can use the moon as a blueprint for impacts that might have happened on the Earth as well.”
“These beads are quite young in age - two billion years and younger, down to a few million years,” she said, adding that they reflected the more recent bombardment history of the moon, which shed light on the Earth’s history.
In the study, the scientists found that one age group of the lunar glass beads coincided precisely with the age of the Chicxulub crater off Mexico, which was formed by the celestial object responsible for the dinosaur extinction 66 million years ago.
They also found that this large terrestrial impact crater event could have been accompanied by smaller impacts, which the researchers will further analyse.
Miljkovic said more samples collected from different parts of the moon would enable scientists to understand the full variation and history of bombardment on the moon, and from it they could infer information about impacts on Earth.
“It should suggest the variations in the so-called impact rate - how often do you get impacts,” she said, adding that there would also be spikes over time.
“Ultimately, everything about planetary science is figuring out where we came from and how we came to be on Earth, and nowhere else,” she said.
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