Press release: The Moon: a chunk ejected from Earth?
No. 8 - 15.01.2025
Researchers from Göttingen in Germany shed new light on the formation of the Moon and origin of water on Earth
A research team from the University of Göttingen and the Max Planck Institute for Solar System Research (MPS) has discovered another piece in the puzzle of the formation of the Moon and water on Earth. The prevailing theory was that the Moon was the result of a collision between the early Earth and the protoplanet Theia. New measurements indicate that the Moon formed from material ejected from the Earth's mantle with little contribution from Theia. In addition, the findings support the idea that water could have reached the Earth early in its development and may not have been added by late impacts. The results were published in the Proceedings of the National Academy of Sciences (PNAS).
The researchers analysed oxygen isotopes from 14 samples from the Moon and carried out 191 measurements on minerals from Earth. Isotopes are varieties of the same element that differ only in the weight of their nucleus. The team used an improved version of “laser fluorination”, a method in which oxygen is released from rock using a laser. The new measurements show a very high similarity between samples taken from both Earth and the Moon of an isotope called oxygen-17 (17O). The isotopic similarity between Earth and Moon is a long-standing problem in cosmochemistry for which the term “isotope crisis” had been coined.
“One explanation is that Theia lost its rocky mantle in earlier collisions and then slammed into the early Earth like a metallic cannonball,” says Professor Andreas Pack, Managing Director of Göttingen University’s Geoscience Centre and Head of the Geochemistry and Isotope Geology Division. “If this were the case, Theia would be part of the Earth's core today, and the Moon would have formed from ejected material from the Earth's mantle. This would explain the similarity in the composition of the Earth and the Moon.”
The data obtained also provide an insight into the history of water on Earth: according to a widespread assumption, it only arrived on Earth after the formation of the Moon through a series of further impacts known as the “Late Veneer Event”. As the Earth was hit much more frequently by these impacts than the Moon, there should also be a measurable difference between the oxygen isotopes – depending on the origin of the material that impacted. “However, since the new data shows this is not the case, many types of meteorites can be ruled out as the cause of the ‘late veneer’,” explains first author Meike Fischer, who was working at the Max Planck Institute for Solar System Research in Göttingen at the time of the research. “Our data can be explained particularly well by a class of meteorites called ‘enstatite chondrites’: they are isotopically similar to the Earth and contain enough water to be solely responsible for the Earth's water.”
Original publication: Meike Fischer et al. Oxygen isotope identity of Earth and Moon with implications for the formation of the Moon and source of volatiles. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2321070121
Contact:
Professor Andreas Pack
University of Göttingen
Geosciences Centre – Geochemistry and Isotope Geology
Goldschmidtstraße 1
37073 Göttingen, Germany
Email: apack@uni-goettingen.de
www.uni-goettingen.de/en/78572.html