Humans haven't been on the Moon for 49 years but samples they took continue to provide new discoveries.
New analysis of a rock sample taken during Apollo 17, which touched down in late 1972, suggest the history of the Moon is more complex than previously thought, according to authors of a report in Nature Communications.
William Nelson, a graduate student at the University of Hawaii, and his colleagues examined troctolite samples using high-resolution electron probe microanalysis X-ray mapping. The team measured the concentration of phosphorus within the rock and found that diffusion patterns preserved in mineral grains were consistent with a rapid cooling history of around 20 million years at high temperatures. Earlier estimates of a 100-million-year cooling duration had prompted debate for 45 years.
Astronauts on the final Apollo mission were commander Eugene Cernan, command module pilot Ronald Evans, and lunar module pilot Harrison Schmitt, who collected the troctolite sample near the base of the North Massif.
The samples were collected when Chuck Berry's "My Ding-a-ling" was the number-one single in the UK, but the latest analysis suggest a renaissance in lunar geological research, according to an accompanying paper.
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Tabb Prissel, a planetary research scientist at NASA's Johnson Space Center, and Kelsey Prissel, a post-doctoral researcher at the Carnegie Institution for Science in Washington DC, said that much of the geochemical understanding of planetary evolution is down to NASA's Apollo and the Soviet Union's Luna (1976) sample return missions.
While the Chinese Lunar Exploration Program promises new data – the Chang'e 5 mission recovered samples in December 2020 – and NASA's recently launched Artemis programme aims to send humans back to the Moon and establish a pitstop on the way to Mars, sealed Apollo samples await opening and first analysis through the Apollo Next Generation Sample Analysis initiative.
"Even samples that have been extensively studied still hold secrets to be unveiled by modern analytical techniques, making 'old' new once more," they said.
"Technological advancements post-Apollo Era have facilitated breakthroughs in lunar science. For instance, the discovery of water within lunar volcanic glasses and apatites [phosphate minerals] uprooted over 40 years of consensus that the Moon was nominally anhydrous [containing no water].
"Now, perhaps more than ever, we recognize the value not only of exploring our solar system but also returning home." ®