Chinese rover sheds light on lunar mantle

PTI Beijing | Updated on May 16, 2019 Published on May 16, 2019

The mission may help unlock secrets of Earth and Moon’s evolution

China’s Chang’e-4 mission, the first to perform a soft landing on the far side of the Moon, has shed light on the chemical and mineralogical composition of the lunar mantle, an advance that could unravel the mystery of the evolution of Earth and its natural satellite.

The Chinese spacecraft became the first misson to land on the lunar far side also known as the dark side of the moon in January. The rover Yutu-2 then rolled off the lander to explore its surroundings. Using data obtained by the visible and near infrared spectrometer installed on Yutu-2, a research team led by Li Chunlai, with the National Astronomical Observatories of China under the Chinese Academy of Sciences, found that the lunar soil in the landing area of the Chang’e-4 probe contains olivine and pyroxene which came from the lunar mantle deep inside the Moon.

The first important scientific discovery of the Chang’e-4 probe was published online in the latest issue of the academic journal Nature. The Moon comprises a core, mantle and crust, like the Earth. With the evolution of lunar magma, the light plagioclase rose to the upper layer to form the lunar crust, while the heavier olivine and pyroxene sank to form the lunar mantle, Li said. “But since the lunar crust is very thick, and there has been no volcanic activity and plate movement on the Moon for billions of years, it’s hard to find materials from the lunar mantle on the surface,” Li told State-run Xinhua news agency.

As a result of the tidal locking effect, the Moon’s revolution cycle is the same as its rotation cycle, and the same side of the Moon always faces the Earth.

The lunar far side, which is turned away from Earth, is more rugged than the familiar near side and has fewer “maria” - dark plains formed by ancient volcanic eruptions. The rover landed inside a 180 kilometer wide impact bowl called Von Karman crater. But that smaller crater lies within the 2,300 kilometer wide South Pole Aitken (SPA) Basin, which covers nearly a quarter of the Moon’s circumference.

The rover has now identified rocks with a very different chemical make-up to those found elsewhere on the moon, the report said. Early results from the rover’s Visible and Near Infrared Spectrometer (VNIS) suggest the rocks contain minerals known as low-calcium (ortho) pyroxene and olivine. They fit the profile of rocks from the lunar mantle and suggest that the ancient impact that created the SPA drove right through the 50-kilometer deep crust into the mantle.

Analysis showed the lunar soil in the landing area contains a large amount of olivine, low-calcium pyroxene and a small amount of high-calcium pyroxene, which are very likely from the lunar mantle, Li said.

Published on May 16, 2019
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