The retention of materials by the Moon

A discovery published in Nature has established that the rate of retention of impact hammers by the Moon is lower than expected. This would explain the absence of valuable materials on our Satellite.


The discovery

Published in Nature, the study by Zhu et al. shows how the measurement of lunar rocks is heavily depleted in precious metals compared to the Earth. This implies that the ratio between the mass added to the Earth during late growth and that added to the Moon is greater than 1,000:1. Late growth is related to the release of water and other volatile elements on Earth, and this is probably a key factor for the habitability of our planet. Through myriad laboratory simulations, Zhu and his colleagues examined the mass fraction of the impactor that could be retained by planetary bodies, discovering that they found that material from larger impactors is retained less effectively than that of their smaller counterparts. 

The retention of materials by the Moon
Fonte: Figure 1 | Lunar glancing blows and direct hits. a, Zhu et al.6 show that the Moon’s ability to retain material from an impactor depends on the angle of the impact with respect to the lunar surface. Low-angle impacts (glancing blows) can result in 80% of the impactor material being lost. The Moon’s rocky mantle and metallic core are shown. b, By contrast, high-angle impacts (direct hits) lead to a substantial fraction of the impactor material being retained. After the impact (see inset), a crater forms, and the impactor material can be incorporated into both the lunar crust and mantle.

Still, making some studies on some of the lunar craters, it has been shown that the retention of the lunar mass has changed slightly over time, equal to about 20%, but still 3 times lower than previous estimates.

Experts’ interpretation

The fact therefore that mass retention implies several conclusions. First, the idea that precious metals were lost 4.5 to 5 billion years ago with the outbreak of the Big Bang is certainly difficult to prove. The loss of precious metals in a metal core can lead to the fractionation of these elements from each other.

See the other articles in the “Space” section of our blog.

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