China's lunar rover Yutu ends 60-year riddle of moon's mantle with discovery of mineral olivine

By Stephen Chen / | May 16, 2019 12:25 PM SGT
China's lunar rover, Yutu, has made a groundbreaking discovery that proves what scientists have been thinking for decades: that the moon has a mantle.
Scientists have long suspected that the moon has a mantle under its crust, just like the Earth, but for the past 60 years lunar explorations, including the US Apollo missions, have failed to provide proof. While there were clues, there was no direct evidence.
"Now we have it," said Professor Li Chunlai, deputy director of the National Astronomical Observatory of China and a lead scientist on the Chang'e-4 mission that put Yutu, or Jade Rabbit as it is known in English, on the moon.
The findings, published in the latest issue of journal Nature on Thursday, answer some fundamental questions about the moon, such as its internal structure and history of its formation.
The rover discovered olivine in surface samples collected near its landing site. Photo: Xinhua
During its first mission on January 3, Yutu discovered olivine, a green, crystallised mineral usually found deep underground " like the upper mantle of the Earth " in surface samples collected near its landing site.
Further analysis showed that the olivine was not local, but had originated from a 72km diameter (45-mile) crater nearby.
The far side of the moon has more craters than the near side, which faces the Earth, and a meteor strike probably penetrated to the mantle and brought up materials to the surface.
Yutu's landing site used to be littered by rocks, but cosmic rays and solar wind weathered them to dust, Li said.
"What we found is the first direct evidence of materials from deep below the lunar crust," though how deep is still unknown, he said.
It is generally believed that the moon was once covered by oceans of molten rock. Lighter substances rose to the surface and formed a crust while heavier ones sank to form the mantle and core. The new findings support that theory.
The first Chinese astronauts will land on the moon between 2025 to 2030, according to Beijing's latest schedule.
The Apollo missions brought back many rock samples, some of which contained olivine, but some scientists suspected they might have come from a volcanic eruption.
China, the United States and other nations have all announced plans to launch missions to exploit the moon's resources within the next decade or two.
Yutu's discovery could help scientists to draw a more accurate map of those resources, including the volume and distribution of minerals, researchers said.
In Chinese folklore, Yutu or Jade Rabbit as it is known in English, is a companion of the moon goddess Chang'e. Photo: Handout
US President Donald Trump gave Nasa an additional US$1.6 billion budget to put Americans back on the moon by 2024.
Li said Chinese scientists were willing to work with their colleagues in the US, but Washington had blocked any such collaboration.
"Our door remains open," he said.
This article originally appeared in the South China Morning Post (SCMP), the most authoritative voice reporting on China and Asia for more than a century. For more SCMP stories, please explore the SCMP app or visit the SCMP's Facebook and Twitter pages. Copyright © 2019 South China Morning Post Publishers Ltd. All rights reserved.
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