Geologist Harrison Schmitt performs Moon tasks during Apollo 17 mission in December 1972.
Credit: NASA

 

A new study has determined that the Moon is significantly older than previously believed. Earlier research had estimated the Moon to have formed approximately 150 million years after the solar system’s formation.

This new finding has been spearheaded by Earth scientists at the University of Cologne’s Institute of Geology and Mineralogy, constraining the age of the Moon to roughly 50 million years after the formation of the solar system – 4.56 billion years ago.

Apollo 12 sample is an ilmenite basalt. It has glass on it, deposited by the splash of material when another basalt was struck by an impactor. Samples like 12054 allow scientists to reconstruct the history of the Moon with the stories they tell.
Credit: Maxwell Thiemens

Range of samples

To achieve these results, the scientists analyzed the chemical composition of a diverse range of samples – nearly 30 specimens — collected during the Apollo lunar landing missions.

Determining the age of the Moon is also important to understand how and at which time the Earth formed, and how it evolved at the very beginning of the solar system.

Earth’s Moon is likely to have 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.

Earth’s Moon continues to surprise.
Credit: NASA

The newborn Moon was covered in a magma ocean, which formed different types of rocks as it cooled. These time capsules have recorded information about the formation of the Moon, and are found today on the lunar surface.

Natural radioactive clock

The Cologne 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 Moon’s mare basalts, i.e., the black regions on the lunar surface. The study could identify distinct trends amongst the different suites of rocks, which now allows for a better understanding of the behavior of these key rare elements.

According to a University of Cologne press statement:

“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.”

Credit: JAXA/NHK

Timing and evolution

Maxwell Thiemens, former University of Cologne researcher and lead author of the study notes: “Mankind’s first steps on another world exactly 50 years ago yielded samples which let us understand the timing and evolution of the Moon. As the Moon’s formation was the final major planetary event after Earth’s formation, the age of the Moon provides a minimum age for Earth as well.”

The study — Early Moon formation inferred from hafnium-tungsten systematics — was published in the journal Nature Geoscience.

More information about this research paper can be found here:

https://www.nature.com/articles/s41561-019-0398-3

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