The Moon is Older Than Previously Believed
martyb writes:
The Moon is Older Than Previously Believed:
The Moon likely formed in the aftermath of a giant collision between a Mars-sized planetary body and the early Earth. Over time, the Moon accreted from the cloud of material blasted into Earth's orbit. The newborn Moon was covered in a magma ocean, which formed different types of rocks as it cooled.
[...] scientists used the relationship between the rare elements hafnium, uranium and tungsten as a probe to understand the amount of melting that occurred to generate the mare basalts, i.e., the black regions on the lunar surface. Owing to an unprecedented measurement precision, the study could identify distinct trends amongst the different suites of rocks, which now allows for a better understanding of the behaviour of these key rare elements.
Studying hafnium and tungsten on the Moon are particularly important because they constitute a natural radioactive clock of the isotope hafnium-182 decaying into tungsten-182. This radioactive decay only lasted for the first 70 million years of the solar system. By combining the hafnium and tungsten information measured in the Apollo samples with information from laboratory experiments, the study finds that the Moon already started solidifying as early as 50 million years after solar system formed. 'This age information means that any giant impact had to occur before that time, which answers a fiercely debated question amongst the scientific community regarding when the Moon formed,' adds Professor Dr Carsten Mi1/4nker from the UoC's Institute of Geology and Mineralogy, senior author of the study.
Journal Reference:
Maxwell M. Thiemens, Peter Sprung, Rail O. C. Fonseca, Felipe P. Leitzke, Carsten Mi1/4nker. Early Moon formation inferred from hafnium-tungsten systematics. Nature Geoscience, 2019; DOI: 10.1038/s41561-019-0398-3
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