China's sample from Moon surface reveals lava eruptions
New Delhi : China's Chang'e-5 lunar mission came to earth with a sample of 2kg of rocky fragments and dust from the Moon collected during the mission. At the ongoing Europlanet Science Congress (EPSC) 2021 virtual meeting, Yuqi Qian, a PhD student at the China University of Geosciences, talked about the initial stage findings from the study done on the sample.
Chang'e-5 landing site was different from the one of the US and other Soviet missions, leading to a different sample collection. It retrieved fragments of the youngest lunar rocks ever brought back for analysis in laboratories on Earth. The rocks are also different to those returned decades ago.
According to the Europlanet Society, the study presented by Qian suggests that 90% of the materials collected by Chang’e-5 likely derive from the landing site and its immediate surroundings, which are of a type termed ‘mare basalts’. These volcanic rocks are visible to us as the darker grey areas that spilled over much of the nearside of the Moon as ancient eruptions of lava. Yet 10% percent of the fragments have distinctly different, ‘exotic’ chemical compositions.
The 10% fragments which are not lava remains will play a crucial role in determining the surface type of the Moon in other parts. Qian and colleagues from Brown University and the University of Münster have looked at the potential sources of beads of rapidly cooled glassy material. They have traced these glassy droplets to extinct volcanic vents known as ‘Rima Mairan’ and ‘Rima Sharp’. These fragments could give insights into past episodes of energetic, fountain-like volcanic activity on the Moon, the release said.
The team has also looked at the potential sources of impact-related fragments. The young geological age of the rocks at the landing site narrows the search, as only craters with ages less than 2 billion years can be responsible, and these are relatively rare on the side of the Moon that faces Earth. The team has modelled the potential contributions from specific craters: Aristarchus, Kepler, Copernicus, Harding, and Harpalus. Qian’s findings show that Harpalus is a significant contributor of many exotic fragments among Chang’e-5’s sample haul, and these pieces of rock could offer a way to address persisting uncertainty about this crater’s age, the release said.
