Scientists Study the Apollo Mission Samples to Identify the Origins of the Moon; Are Delighted by The Results

The moon has always been an intriguing object for space aficionados. Astronomers have conducted many missions and analyses dedicated to the natural satellite, but despite that one question regarding the body always remained unanswered, the date of its origin. Researchers from the University of Chicago, in their latest examination, strive to solve this mystery. They made use of lunar rocks from Apollo missions, to fulfill their objective. Findings regarding this investigation have been published in the Proceedings of the National Academy of Sciences.

Past studies have confirmed that the moon was formed due to a collision between Earth and a huge extraterrestrial object. The impact created two balls of molten magma, as per astronomers. Researchers to this date have been unable to figure out how the collision formulated the two magma balls or when the phenomenon took place. To find out the moon's age, experts applied some cutting-edge techniques. 

Researchers speculated that the heated magma balls began to cool down after the collision. They believe most of the magma cooled down in a millennium. After 80% of the magma cooled down, the remaining content came together to form a crust of minerals. The crust insulated the whole structure. Researchers, for decades, have faced difficulty in determining how long the partially molten magma stayed in that state, before cooling and making way for the solid rock that is the moon.

Experts speculated that during the cooling process, a mixture of certain elements moved upwards within the partly molten mantle. This became a distinct layer by itself, containing elements like phosphorous, potassium, lutetium, and other rare earth elements. Researchers, through their examination, wanted to know the age of this layer, labeled KREEP. In this way, they would be able to determine when the moon was 99% crystallized.

Researchers decided to analyze samples brought back by Apollo missions and try to locate the KREEP layer. Experts focussed on lutetium, as their main element for study. The radioactive element changed into hafnium at a predictable rate. This allowed experts to trace its progress backward in rocks similar to radiocarbon dating. In the early solar system, all rocks contained the same amount of lutetium. However in KREEP, conditions weren't favorable for lutetium, and hence there were lower levels of it. By comparing the levels of lutetium and hafnium, in moon rocks and structures from other places in the solar system, but in the same era, researchers hoped they would have an idea when the KREEP layer formed, and by extension when the satellite stopped cooling.

The team had to be judicious with their tests, as the samples were low in number. The analysis showcased that the moon cooled down 4.43 billion years before the present day. The pursuit was not easy at all, but researchers are delighted by the results. "It took us years to develop these techniques, but we got a very precise answer for a question that has been controversial for a long time," said Nicolas Dauphas, the first author of the paper, who heads the UChicago Origins Laboratory and is a professor in the Department of the Geophysical Sciences and the Enrico Fermi Institute.