China 2021-11-16T04:03:08+02:00
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The moon was volcanically active for longer than we thought, analysis of lunar rocks suggests

The moon was volcanically active for longer than we thought, analysis of lunar rocks suggests

science, China, space, PRC, Moon, Volcanic material
Simulated image of China’s Chang'e-5 spacecraft. Photo by Xinhua/Rex/Shutterstock.
Simulated image of China’s Chang'e-5 spacecraft. Photo by Xinhua/Rex/Shutterstock.

Analysis of the youngest lunar material ever retrieved suggests that the moon was volcanically active for longer than previously expected, The Xinhua News Agency reported.

China’s Chang’e-5 spacecraft retrieved 1.7kg of lunar material when it landed on the moon in December 2020 – the first sample return mission in four decades.

New analysis of the moon rocks suggests they are around 2bn years old – almost 1bn years younger than those previously found. The samples collected were basalts, volcanic rocks formed by the rapid cooling of lava.

Prof Alexander Nemchin of Curtin University, a co-author of the study, said the research shed light on the history of the moon at a time when it was thought to be cooling down and its magnetic field diminishing.

"The expectation is that small bodies cool very fast … and they become dead and nothing happens", – he said.

The moon at that point should have been cold, but the age of the samples suggests there must have been a heat source in the region to explain the later-than-expected volcanic activity.

Knowing the precise age of the moon rocks will also help scientists better calibrate a technique for dating planetary surfaces when no samples are available.

The technique estimates the age of a surface based on the density of impact craters – older surfaces have greater and more craters than younger surfaces.

The volcanic material was collected from a previously unexplored part of the Oceanus Procellarum (Ocean of Storms), on the near side of the moon.

"We can link the number of craters (there) to a specific age", – Nemchin said. "Then you go to an area where you don’t have a sample and you can use this relationship to determine the age."

The relationship between crater number and age was previously not well known between 1bn and 3bn years ago.

"This 2bn year (age) places us right in the middle of this gap", – Nemchin said. "We’ve got the possibility to determine this approach much better."

The team was granted access to study two grams of the total 1.7kg in lunar dust and debris, which is held at laboratories at China’s National Astronomical Observatories in Beijing.

"Tests on the sample, including lead isotope dating, were conducted in Beijing. The team analysed the abundance of different elements with a focused oxygen beam, which targeted a "tiny spot on the surface of the sample" at a time, about five microns in diameter and one micron deep", – Nemchin said.

China is the third country to have retrieved samples from the moon, after the US’s Apollo missions and the Soviet Union’s Luna missions in the 1960s and 70s. The last moon rocks were collected in 1976 by the Soviet Union’s Luna 24.

The study was published in the journal Science.

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