December last year, the Chinese Chang’e-5 lunar lander landed in Mongolia, carrying with it the world’s first fresh batch of Moon rocks and dust since 1976. Since its touchdown, scientists have combed over what the lander brought back with it, and in doing so, have unraveled what appears to be a new phase of lunar research. The lander carried with it what are currently the youngest-known Moon rocks ever obtained—rewriting what we know about the Moon’s history. The study which details this landmark find, led by the Chinese Academy of Geological Sciences, was published in the journal Science.
These rocks were dated by an international team of scientists, who determined the rocks to be 1.97 billion years old. These dates make these Moon rocks “the youngest volcanic rocks identified on the Moon so far,” according to co-author and Curtin University professor Alexander Nemchin.
“It is the perfect sample to close a 2-billion-year gap,” said Brad Jolliff, the Scott Rudolph Professor of Earth and Planetary Sciences in Arts & Sciences and the McDonnell Center for the Space Sciences director in Washington University in St. Louis. The “gap” scientists like Joliff refer to are the apparent gap in the age of volcanic Moon rocks obtained by the Apollo missions, which were dated as being more than 3 billion years old, and the age of rocks from lunar impact sites, which were determined to be younger than a billion years old.\
Scientists take advantage of the absence of otherwise erosive processes which shape the Moon’s surface. Being 4.5 billion years old—around the same age as Earth—scientists are presented with room for analysis by using the constant presence of craters; the more craters a region has, the older it probably is. Results from the Chang’e-5 lander helped ascertain these hypotheses. As mentioned by Jolliff: “[To] put absolute age dates on [the lunar surface], one has to have samples from those surfaces.”
Jolliff calls this finding a “phenomenal result,” as the findings by the Chang’e-5 lander gathered rocks at a “very precise age right around 2 billion years, plus or minus 50 million years.” To them, “that’s good enough to distinguish between the different formulations of the chronology.”
Said Professor Gretchen Benedix, also from Curtin University: “These results confirm what experts had long predicted based on remotely obtained images of the Moon and raise further questions as to why these young basalts exist.” The entire process of dating these Moon rock samples, the authors say, will help inform future expeditions to other rocky worlds in the Solar System.
The Chang’e-5 mission makes China the third country to ever bring back samples from the Moon, after the United States of America and the Soviet Union. China hopes to complete more lunar explorations this decade with the Chang’e-6. 7, and 8 missions.
(Read further about the Moon’s past with our piece on what could be a more extensive bombardment phase during its infancy than previously thought.)
References
- Che, X., Nemchin, A., Liu, D., Long, T., Wang, C., Norman, M. D., Joy, K. H., Tartese, R., Head, J., Jolliff, B., Snape, J. F., Neal, C. R., Whitehouse, M. J., Crow, C., Benedix, G., Jourdan, F., Yang, Z., Yang, C., Liu, J., … Webb, S. G. (n.d.). Age and composition of young basalts on the Moon, measured from samples returned by Chang’e-5. Science, 0(0), eabl7957. https://doi.org/10.1126/science.abl7957
- Lavars, N. (2021, October 8). Youngest Moon rocks ever found shake up understanding of lunar past. New Atlas. https://newatlas.com/space/chang-e-5-youngest-moon-rocks-volcanic-history/
- Washington University in St. Louis. (2021, October 7). Chang’e-5 samples reveal key age of moon rocks: Scientists share analysis of first fresh samples from the moon in more than 40 years. ScienceDaily. https://www.sciencedaily.com/releases/2021/10/211007145754.htm
