A new analysis of a sample of lunar rock collected by astronauts on the Apollo 17 mission reveals that the Serenity basin is even older than previously thought. The formation of this large crater, estimated thanks to new dating techniques and numerical simulations, dates back to 4.2 billion years ago, even before the intense late bombardment that produced many of the impact craters on the Moon.
Even with the naked eye, the Moon shows more or less dark areas which, when observed in more detail, tell the billions of years of history of our natural satellite. While on Earth the meteorological phenomena, water and tectonic activity tend to erase the signs of the celestial bodies that have affected it during its long history, the absence of these elements on the Moon forever preserves the memory of each impact on its surface. Now, by studying a sample of the lunar soil brought back to Earth in 1972 by astronauts from the Apollo 17 mission , the latest in the historic NASA series, an international team of researchers has refined the estimate of the age of the crater known as the Serenitatis basin , or basin. of Serenity, created by an impact 4.2 billion years ago .
Since the first observations, the Serenity basin – which includes the most famous sea of Serenity , the landing site not only of Apollo 17 but also of the Soviet robotic mission Luna 21 in 1973 – has been considered one of the oldest of the great craters on the face of the Moon turning towards our planet. Estimating its age through the analysis of the rocks collected by astronauts was one of the scientific objectives of the Apollo 17 mission – the one that, among the six landed on the lunar surface, brought back most of the samples, over one hundred kilos. In the past, analysis of the samples from this mission had associated most of them with a more recent impact, linked to the formation of the nearby Imbrium basin, whose material would have been thrown over great distances, covering much of the ‘near face’ of the Moon. This mixing complicates the determination of the actual age of the Serenity basin, initially indicating a value of approximately 3.8–3.9 billion years.
The new study, based in particular on a rock collected by astronauts at Station 8 on the route of their second extravehicular activity, now pushes this estimate back by 300 million years . The results of the research, led by the Open University (UK) and with the participation of researchers from the University of Portsmouth (UK), the Royal Ontario Museum, the University of Toronto and the Université de Sherbrooke (Canada), Swedish Museum of Natural History (Sweden) and Curtin University (Australia), have been published in Nature Communications Earth and Environment .
“We have long observed this fascinating specimen and tried to unravel its complex radiogenic ages,” says lead author Ana Černok of the Open University, Royal Ontario Museum and the University of Toronto. “It has been difficult to establish the exact link of the samples with the Serenitatis basin since the Apollo 17 collection was reported, because it was not easy to distinguish between the samples formed by the Imbrium event and those formed by Serenitatis.”
To obtain accurate dating of the sample, the team used an innovative technique from materials science, atomic probe tomography , along with numerical simulations of the impacts. The combination of these methods made it possible to link the microscopic-scale study of a small sample of the moon to the moment when, billions of years ago, a celestial body hit the surface of the Moon. «The dating techniques (uranium-lead geochronology) have suggested that this sample of the Serenitatis basin on the Moon is very old, about 4.2 billion years, that is, only about 350 million years younger than the entire Solar System, making it a precious sample for knowing the primordial evolution of the Moon and the origin of our planet “, explains the co-authorKatarina Miljkovic , associate professor at Curtin University.
In the history of the Earth-Moon system, this result indicates that the crater may even precede the beginning of the ‘ late heavy bombardment – in English late heavy bombardment (LHB), or the time during which the planets of the inner solar system were subjected to numerous impacts from asteroids and comets, which is between 4.1 and 3.8 billion years ago. Alternatively, the new measure could call into question the very duration of the Lhb, in support of a more prolonged period whose very early stages could coincide with the formation of the Serenitatis basin.
The new-technique analysis of a long-studied lunar sample also offers a new key to studying the atomic-scale processes occurring in minerals hit by extreme astronomical impacts. The distribution of the atoms in the analyzed sample, Miljkovic points out, shows that it “underwent not one, but two impact events. The second impact transported the sample close to its resting place where it was collected by the astronauts ».
Featured image: The Serenity basin, one of the oldest craters on the near side of the Moon, landing site for the Apollo 17 mission. Credits: Wikipedia
To know more:
- Read on Nature Communications Earth and Environment the article ” Lunar samples record an impact 4.2 billion years ago that may have formed the Serenitatis Basin ” by Ana Černok, Lee F. White, Mahesh Anand, Kimberly T. Tait, James R. Darling, Martin Whitehouse, Katarina Miljković, Myriam Lemelin, Steven M. Reddy, Denis Fougerouse, William DA Rickard, David W. Saxey and Rebecca Ghent
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