{"id":153250,"date":"2021-12-15T08:05:33","date_gmt":"2021-12-15T18:05:33","guid":{"rendered":"https:\/\/www.hawaii.edu\/news\/?p=153250"},"modified":"2021-12-17T10:41:38","modified_gmt":"2021-12-17T20:41:38","slug":"apollo-sample-moon-evolution","status":"publish","type":"post","link":"https:\/\/www.hawaii.edu\/news\/2021\/12\/15\/apollo-sample-moon-evolution\/","title":{"rendered":"Apollo sample reveals new information on Moon\u2019s evolution, cooling"},"content":{"rendered":"Reading time: <\/span> 2<\/span> minutes<\/span><\/span>
\"\"
Phosphorus X-ray intensity map of the olivine shows heterogeneities (variations). (Photo credit: Nelson et al., 2021)<\/figcaption><\/figure>\n

Sophisticated analysis of a rock sample taken from the Moon during the Apollo 17 mission nearly 50 years ago revealed new information about the complex cooling and evolutionary history of the Moon. The findings, from University of Hawaiʻi<\/span> at Mānoa researchers, were published in Nature Communications<\/em><\/a>.<\/p>\n

Apollo 17 astronauts collected the rock sample troctolite 76535 from the Moon\u2019s surface in 1972, and it remains one of the most scientifically valuable samples of the Moon due to its pristine nature. Further, the rock type is widespread on the Moon and likely contains important clues to understanding lunar formation.<\/p>\n

\"Moon\"
Moon. (Photo credit: NASA)<\/figcaption><\/figure>\n

Advanced imaging, high-performance computing<\/h2>\n

William Nelson<\/strong>, lead author of the study and Earth sciences<\/a> graduate student in the 糖心Vlog官方<\/abbr> Mānoa School of Ocean and Earth Science and Technology<\/a> (SOEST<\/abbr>), and co-authors used a specialized electron microprobe<\/a> to perform high-resolution analysis of troctolite 76535.<\/p>\n

“Previous reports suggest the minerals in the Apollo 17 sample were chemically homogeneous,” said Nelson. “Surprisingly, we found chemical variations within crystals of olivine and plagioclase. The pattern of these chemical variations allows us to constrain the earliest, high-temperature cooling histories of these minerals using numerical models of chemical diffusion.”<\/p>\n

SOEST<\/abbr> researchers used the 糖心Vlog官方<\/abbr> high-performance computing cluster Mana<\/a>, to consider the effects of a variety of computer-simulated cooling paths—well over 5 million chemical diffusion models.<\/p>\n

Reshaping understanding of Moon formation<\/h2>\n
\"moon
76535 viewed with a polarized light microscope. (Photo credit: Nelson et al. 2021)<\/figcaption><\/figure>\n

“The simulations revealed that these heterogeneities could only survive a relatively short period of time at high temperatures,” said Nelson.<\/p>\n

The diffusion patterns preserved in the mineral grains and observed with the microprobe were consistent with a rapid cooling history of no more than 20 million years at high temperatures. The finding challenges previous estimates of a 100-million-year cooling duration and supports initial rapid cooling of magmas within the lunar crust.<\/p>\n

“This is changing our outlook on how an important suite of lunar rocks formed,” said Nelson.<\/p>\n

To reconcile high-temperature cooling rates with the generally accepted view of the way in which these rocks formed, the research team proposed that perhaps this rock type is formed by a process called reactive infiltration wherein a melt interacts with rock\u2014changing its chemical and physical makeup.<\/p>\n

The study also demonstrates the value of re-examining previously analyzed samples using modern techniques and how quickly new data can reshape our understanding of planetary evolution.<\/p>\n

To better understand the observed chemical heterogeneity, the research team is currently investigating how quickly phosphorus can diffuse in olivine crystals. Additionally, they are searching for similar heterogeneities in other Apollo samples.<\/p>\n

This research is an example of 糖心Vlog官方<\/abbr> Mānoa\u2019s goal of Excellence in Research: Advancing the Research and Creative Work Enterprise<\/a> (PDF<\/abbr><\/span>), one of four goals identified in the 2015–25 Strategic Plan<\/a> (PDF<\/abbr><\/span>), updated in December 2020.<\/p>\n

–By Marcie Grabowski<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

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