Zircon crystals serve as timestamps for impact events on the Moon
Researchers have precisely dated zircon crystals from the Moon and found that most of the analysed crystals are around 4.338 billion years old. They bear witness to a huge impact at the South Pole of the Moon and shed new light on the early phase of our solar system.
Defining our Moon's origin and how it formed from a dramatic collision between Earth and another body the size of Mars several billions of years ago has been a topic of discussion by researchers for decades.
Analysing data from lunar zircon crystals collected during the Apollo missions, a team of researchers led by Melanie Barboni of Arizona State University and Dawid Szymanowski of ETH Zurich unearthed a remarkable concentration of zircon ages, all tightly clustered around 4.338 billion years.
If the team is correct, the zircon age peak could mark the enormous impact that created the South Pole-Aitken basin on the far side of the Moon—the largest known impact crater in the solar system spanning over 2000 km wide. The results of their study were recently published in Science Advances.
An impact of this magnitude would have excavated lunar mantle material from great depths. The recent study suggests the zircons Barboni and Szymanowski dated likely crystallised within the impact melt sheet as it cooled and differentiated. Subsequent impacts could have then distributed these zircons across the lunar surface.
If the dated zircons indeed correspond to the South Pole-Aitken impact, it will confirm this basin as one of the oldest on the Moon, serving as a crucial reference point for early lunar chronology. An impact of such magnitude would have also played a significant role in shaping the development of the lunar crust and mantle.
Barboni and Szymanowski's analysis proposes some exciting implications for the state of the early solar system over 4.3 billion years ago. An impact of the size of South Pole-Aitken hints at a still dynamic solar system, with large objects continuing to collide with planets and moons. If the Moon experienced such dramatic events, the Earth likely did as well. This research opens up a fascinating window into the dynamic early solar system.
Reference
Barboni M, Szymanowski D, Schoene B, et al. High-precision U-Pb zircon dating identifies a major magmatic event on the Moon at 4.338 Ga. Science Advances, 10, eadn9871 (2024). doi: external page10.1126/sciadv.adn9871
The analyses were conducted at the high-precision U-Pb geochronology lab at Princeton University, the Origins Lab at the University of Chicago, and at the UCLA Ion Microprobe Laboratory. The co-author Dr. Dawid Szymanowski is now a postdoctoral researcher at the Institute of Geochemistry and Petrology at ETH Zurich, working in the research group of Prof. Cyril Chelle-Michou.
Summary of the article “external pageZircon crystals serve as time stamps for lunar impact events”, published by Arizona State University.