The history of the Moon may be more complicated than previously imagined, according to a new examination of a rock sample retrieved during Apollo 17, which landed in late 1972.
Most of our present understanding of lunar evolution comes from rocks recovered by astronauts during NASA's Apollo mission half a century ago, yet they can still provide fresh information. Researchers detailed their study, titled "A Lunar Sample Renaissance," in Nature Communications.
Apollo 17 Rock Sample Says Moon Cools Faster Than Everyone Thought
William Nelson of the University of Hawai'i at Mnoa and his colleagues reexamined troctolite 76535, one of the collection's most well-studied rocks. It's around 156 grams in weight and 5 cm broad at its widest point. The sample belongs to a collection known as the magnesian suite (Mg-suite). These rocks indicate the beginnings of secondary crust development, which occurred when the lowest regions of the Moon's mantle came to the surface and crystallized.
Nelson and his colleagues discovered that phosphorous was distributed unevenly throughout the sample using high-resolution analytical methods. It indicates that the rock cooled fast since the element did not have enough time to disperse evenly throughout the rock before solidifying. The scientists then calculated that the sample must have taken roughly 20 million years to solidify from its molten form using computer modeling. This cooling time is far less than prior predictions of roughly 100 million years.
This discovery shifts our knowledge of the Moon's evolution and history by 80 million years.
"There's still value to be had in looking back at old samples to try to get a good idea of how the moon as a whole formed," Nelson said per New Scientist. "You can always go back and reanalyse old data sets with new techniques to pull out new nuggets of information."
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Carefully Examining the Past
When studying a moon rock, experts usually use extreme caution. Not only has lunar dust, or regolith, been linked to human health problems, but scientists also want to be cautious with these samples since they are so rare.
"We handled the sample wearing gloves and using a delicate touch," Nelson told Space.com. "As for long-term storage, the lunar sample curation team at NASA's Johnson Space Center preserves these samples and makes them available for scientific research"
Despite the samples being collected during NASA's Apollo program, Nelson believes that much can still be learned from them
While China's Lunar Exploration Program promises new data - the Chang'e 5 mission will return samples in December 2020 - and NASA's recently launched Artemis program aims to send humans back to the Moon and establish a stopover on the way to Mars, The Register said the sealed Apollo samples are awaiting opening and first analysis through the Apollo Next Generation Sample Analysis initiative.
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