Sophisticated analysis of a rock sample taken from the moon during the Apollo 17 mission has revealed new information about the complex cooling and evolutionary history of the moon.
The results of the study, conducted by University of Hawaii (UH) scientists at Manoa, are published in the journal Nature Communications.
The Apollo 17 mission collected the rocky sample “Troctolite 76535” from the surface of the moon in 1972, which is still one of the most valuable samples of the moon from a scientific point of view due to its pristine nature.
Moreover, the type of these rocks are widespread on the surface of the Moon and likely contain clues important to understanding the composition of the Moon.
William Nelson, the study’s lead author and a graduate student in Earth sciences at the University of Hawaii’s School of Oceanic and Earth Science and Technology (SOEST), and co-authors used a specialized electronic probe to perform a high-resolution analysis of troctolite 76535.
“Previous reports indicate that the minerals in the Apollo 17 sample were chemically homogeneous. Surprisingly, we found chemical differences within the olivine and plagioclase crystals. These variations allow us to constrain the earliest high-temperature cooling dates for these minerals using numerical models,” Nelson said.
To look at the effects of a variety of computer-simulated cooling pathways, scientists from the College of Oceanic and Earth Sciences and Technology used high-performance computing facilities to look at the effects of more than 5 million chemical diffusion models.
“The simulations revealed that these heterotrophs can only survive for a relatively short time at high temperatures,” Nelson explained.
The preserved diffusion patterns in the mineral grains observed with the microprobe were consistent with a history of rapid cooling of no more than 20 million years at high temperatures. This discovery challenges previous estimates of a cooling period of 100 million years and supports the initial rapid cooling of magma within the lunar crust.
“This changes our view of how an important group of lunar rocks is formed,” Nelson revealed.
To reconcile high-temperature cooling rates with the generally accepted view of the way these rocks were formed, the research team suggested that this type of rock may have formed through a process called reactive infiltration where the melt interacts with the rocks, leading to a chemical and physical change.
The study also demonstrates the value of re-examining samples that were previously analyzed using modern techniques and how quickly the new data can reshape our understanding of planetary evolution according to rt.
To better understand the observed chemical heterogeneity, the research team is currently studying how quickly phosphorous diffuses into olivine crystals. In addition, they are looking for similar variations in other Apollo samples.
.