Determining the age of the Moon

With more than 30 missions planned to take place by 2030, culminating with the return of humans to the Moon through the NASA Artemis programme, we are currently witnessing an incredibly exciting lunar exploration renaissance more than half a century after the end of the Apollo programme. Studies of samples returned by the Apollo astronauts between 1969 and 1972 have transformed our understanding of how planets form and evolve. And 50 years after these samples were returned to the Earth, we are still making crucial discoveries about the Moon, for example that volcanic rocks from the Moon contain water trapped inside tiny crystals. Yet, many fundamental questions have remained unanswered, such as how and when did the Moon form, and how did the Moon's primordial crust form.
Canonical models postulate that the Moon formed as a result of a giant impact between the proto-Earth and a body called Theia. In these models, the Moon started as partially to wholly molten, a stage known as the lunar magma ocean. During cooling, dense mafic minerals crystallised first and sank to the bottom of the lunar magma ocean; Ca-rich plagioclase then formed and floated atop the lunar magma ocean after 70-80% solidification, forming a global anorthosite crust. Chronological investigations of Apollo samples from this primordial lunar crust have yielded dates clustering around 4.35 billion years - some have argued that this indicates protracted crystallisation of the lunar magma ocean over ~150 million years with a Moon formation 4.5 billion years ago, though others have suggested that the Moon was much younger and only formed shortly before 4.35 billion years ago.
Thanks to detailed remote sensing investigations of the composition of the lunar surface over the past couple of decades, we now know that samples returned by the Apollo missions all originate from an anomalous region of the lunar nearside characterised by elevated abundances of some geochemical elements such as potassium (K), rare...