Scientists Discover Sulfur Anomaly in 50-Year-Old Moon Soil Samples Raising New Theories About Lunar Origins
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| Scientists Discover Sulfur Anomaly in 50-Year-Old Moon Soil Samples Raising New Theories About Lunar Origins. |
A 50-year-old Moon soil sample has revealed a surprising discovery that could reshape scientists’ understanding of our natural satellite. A research team led by James Dottin, an assistant professor of Earth, Environmental, and Planetary Sciences at Brown University, found an unusual sulfur isotope anomaly in volcanic material collected from the Taurus-Littrow region. The samples were gathered during NASA’s Apollo 17 mission in 1972 by astronauts Eugene Cernan and Harrison Schmitt and sealed in a helium-filled metal tube for future studies.
The analysis was conducted as part of NASA’s Apollo Next Generation Sample Analysis (ANGSA) program, which reexamines archived lunar materials using modern technology. Dottin used secondary ion mass spectrometry, a highly precise isotope analysis method that did not exist in the 1970s. The results were astonishing: the volcanic rocks contained sulfur compounds with extremely low levels of the isotope sulfur-33 (³³S), one of four stable sulfur isotopes. This ratio is vastly different from what is found on Earth.
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| Scientists Discover Sulfur Anomaly in 50-Year-Old Moon Soil Samples Raising New Theories About Lunar Origins. |
“At first, I didn’t believe it,” said Dottin. “We went back and checked everything, and it turned out to be correct. The numbers are just so different from anything we’ve ever seen on Earth.” Until now, scientists assumed that the Moon’s mantle had the same sulfur isotope composition as Earth’s. However, these findings suggest something far more complex might be happening beneath the lunar surface.
According to Dottin and his team, there are two possible explanations for this anomaly. The first theory suggests that the sulfur isotope ratios were shaped by chemical reactions in the Moon’s early, short-lived atmosphere. When sulfur interacts with ultraviolet light in a thin atmosphere, it can create depleted ³³S ratios. If that’s the case, it could mean that the samples record ancient material exchange between the Moon’s surface and mantle — a process that occurs on Earth through plate tectonics, which the Moon lacks.
The second theory links the anomaly to the Moon’s origin. The leading hypothesis proposes that a Mars-sized object called Theia collided with the early Earth, and debris from that massive impact eventually formed the Moon. It’s possible that Theia had a distinct sulfur isotope signature, and those differences were preserved in the Moon’s mantle.
For now, scientists cannot say which explanation is correct. Dottin hopes that studying sulfur isotopes from Mars and other celestial bodies in the future will provide more clues. Ultimately, understanding the distribution of sulfur isotope signatures could help scientists piece together the early history and formation of the Solar System.
