It is believed that all activity on the Moon died out about 3 billion years ago: by that time, the temperature of its interior had already dropped below the minimum required level. The Chinese lunar samples, however, prove that volcanic activity continued for at least another billion years.
Scientists have described the results of the analysis of two basalt fragments approximately 2-3 mm in size. As it turned out, they are almost a billion years younger than the lunar samples collected as part of the Soviet and American programs of the last century.
First lunar samples in decades
Collecting and delivering soil samples was the main task of the Chang’e-5 mission, which was launched in December 2020. The lander extracted 1.7 kg of rock from the region known as the Ocean of Storms – scientists believe that this region contains the most “fresh” traces of the volcanic activity of our satellite.
Research
Upon arrival on Earth, the lunar samples were sorted and scientists took several small fragments, which were then examined using the SHRIMP (Sensitive High-Resolution Ion Microprobe) instrument at the Chinese Academy of Geological Sciences, located in Beijing.
Methods
By directing a stream of charged particles at the lunar samples, the scientists were able to separate and analyze material from different mineral phases, which allowed them to establish the age of the rock – 1.97 billion years. This is a billion years less than any other lunar basaltic lava sample studied.
Unexpected results
The discovery puzzled scientists very much. The fact is that in the past, the surface of the Moon was indeed dotted with active volcanoes and covered with oceans of magma – this is how dark “spots” were formed on its surface, known as lunar seas. However, it is believed that all activity on the Moon died out about 3 billion years ago: by that time, the temperature of its interior had already dropped below the minimum required level.
High concentration of fuel elements
The nature of the mysterious heat source that supported the existence of lava on the lunar surface two billion years ago is not yet known. Earlier, it was suggested that there is a high concentration of fuel elements in the mantle and rocks of the satellite (including radioactive isotopes). However, the team did not find a significant difference in these rates between the new lunar samples and those obtained during the space programs of the 20th century.
Tidal heating
Another explanation is tidal heating – the process of heating the bowels due to their deformation under the influence of tidal forces. The last hypothesis is the low melting temperature of the lunar mantle due to its unique composition.
Importance
The team is still working on the lunar samples to shed light on this mystery. A deeper understanding of geological processes will make it easier for us to study other planets, the soil samples of which we do not yet have – for example, Mars, Venus, and Mercury. It could even help in the search for extraterrestrial life because volcanic activity plays a key role in the formation of atmospheres and oceans.
Future Chinese missions
The moon continues to throw new mysteries to scientists, while the PRC is already preparing a new mission to explore the moon – the Chang’e-6 interplanetary station, which is scheduled to be launched in 2024. Together with the Chinese rover, and the construction of its own space station in Earth orbit, we see how China is actively beginning to explore space.
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Sources:
• Bartels, M. (2021, October 7). Moon rocks brought to Earth by Chinese mission fill key gaps in Solar System history. Space.com.
• Bressan, D. (2021, October 11). With 2 billion years, China’s chang’e 5 samples are the Moon’s youngest rocks. Forbes.
• Che, X. (n.d.). Age and composition of young basalts on the Moon, measured from samples returned by Chang’E-5. Science.
• Kreier, F. (2021, October 7). China’s lunar rock samples show lava flowed on the moon 2 billion years ago. Science News.
• Snape, J. (n.d.). China’s Moon Rocks set a record for youngest lunar material: 1.97 billion years old. ScienceAlert.
• Snape, J., Joy, K., & Tartese , R. (2021, October 7). Chang’E-5 samples reveal Moon rocks dating back less than 2 billion years – the youngest we’ve seen. The Conversation.
