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Posted: Jun 05, 2014

Moon formed after collision of planets

(Nanowerk News) Scientists from the Universities of Göttingen, Cologne, and Münster in Germany have resolved an isotopic difference between the Earth and the Moon. The slight variation in oxygen isotopes confirms the “Giant impact“ hypothesis of Moon formation, according to which the Moon formed from the debris of a giant collision between the Earth and another proto-Planet about 4.5 billion years ago.
The results were published in the journal Science ("Identification of the giant impactor Theia in lunar rocks").
In the Stable Isotope Laboratory at Göttingen University’s Geoscience Centre, the scientists analyzed samples from the Moon that were provided by NASA. The lunar basalts were brought back to Earth between 1969 and 1972 with Apollo Missions 11, 12, and 16. They released the oxygen from the rocks, purified it and measured the pure oxygen gas in the mass spectrometer.
“For the first time, we were able to show a subtle difference between the rare 17O isotope and the abundant 16O isotope,” explains Dr. Daniel Herwartz, who lead the study at Göttingen University and is now employed at the University of Cologne. “The similar isotopic composition of Earth and Moon appeared to be at odds with the giant impact hypothesis, because numerical models of the collision predicted a difference. The difference we found is smaller than initially predicted, but that might be due to the fact that both planets originated from the same region of the solar system.”
Only a few laboratories worldwide are able to measure the rare 17O isotope at all. “For the last three years, staff and students in Göttingen have persistently worked on improving the analytical procedure,” says Prof. Dr. Andreas Pack, head of the Stable Isotope Laboratory at Göttingen University’s Geoscience Centre. “The results of this study show that this effort has paid off.” Some of the data were measured by student Bjarne Friedrichs for his Bachelor’s thesis.
Source: Georg-August-Universität Göttingen
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