Chinese scientists reveal late surges in moon's volcanic activity

Photo provided by the China National Space Administration (CNSA) shows Chang'e-5 probe gathering samples on the moon on Dec. 2, 2020. (CNSA/Handout via Xinhua)

BEIJING, July 7 (Xinhua) -- Chinese researchers have studied the lunar samples brought back by the Chang'e-5 mission and found surges in volcanic activity on the moon about two billion years ago, offering a window into the moon's late-stage evolution.

The study, conducted mainly by a research team at the Institute of Geology and Geophysics under the Chinese Academy of Sciences, was published recently in the journal of Nature Communications.

At the end of 2020, China's Chang'e-5 mission retrieved samples from the moon weighing about 1,731 grams, which were the first lunar samples in the world in over 40 years.

In the subsequent research, Chinese scientists dated the youngest rock on the moon at around 2 billion years in age, meaning that the period of lunar volcanism was between 800 and 900 million years longer than previously believed.

"This study further answered the question of how much magma spewed out during the moon's late period," said Tian Hengci, corresponding author of the study, told the China Science Daily.

He added that the formation age of basalt, its geochemical characteristics and cooling timescales are critical to understanding the scale of a lunar magma eruption.

Based on previous work, the research team found that the Chang'e-5 basalt is likely to be the result of volcanic eruption during the same period, and as it came mostly from the same source, it provides an excellent opportunity to determine the thickness of the basalt lava flow and the scale of the eruption.

Tian said that the cooling rate of magma is fastest at the surface, and it decreases gradually towards the interior. The cooling time and rate of magma can be deduced from changes in certain characteristic elements in minerals in the lunar samples, and based on this, the thickness of the lava flow and the scale of the eruption can be inferred.

Researchers analyzed 21 olivine grains from basalt clasts, and the results indicate that the cooling time of most olivine particles was less than one year. Using a thermodynamic model, they estimated that the thickness of the basaltic lava flow was between 10 and 30 meters.

Based on flat landing area of the Chang'e-5, the research team extrapolated the volume of the basalt eruptions, and this indicated that there were large-scale magma eruptions on the moon about 2 billion years ago. The conclusions are consistent with the results obtained by remote sensing methods.

According to the study, while the overall intensity of lunar volcanic activity may have decreased over time, there may have been episodic eruptions in the moon's late-stage with above-average flux.

Researchers said that the reasons for the large-scale volcanic eruptions found during the late period of the moon are still unclear, and they will work with other teams to establish a thermal evolution model of the landing area to explore the mystery.