Pink Floyd aside, the fascination of what’s called ‘the dark side of the Moon’ is widespread, even though calling it “dark side” is actually a misnomer. As a matter of fact, that side is no darker than any other part of the lunar surface; it is only that it never turns to us, so we can never see it from the Earth’s surface (in astronomy, the phenomenon is known as ‘tidal locking’, and it is common among moons).
A better and more correct name is instead “far side”, and this is how the astronomers call it.
Far or not, we know a great deal about it, and we have for a long time. In fact, 7 October 2019 was the 60th anniversary of the first image of the ‘dark side’ of the Moon, taken by the Soviet Luna 3 spacecraft: it was the very first time that this side of the Moon had ever been seen. From this and following missions, we know that the far side is markedly different from the one we see every night.
The far side is full of impact craters but scarce in maria, the flat basaltic plans that are one of the most characteristic features of the near side. The reason for this asymmetry has puzzled scientists since its discovery, and now they’ve probably found out why: in the different concentration of radioactive elements in the lunar soil.
According to a new study published on March 30, “the asymmetry is linked to a property of KREEP, a rock signature which is short for potassium (chemical symbol K) enriched rock, rare‐earth elements (REE — which includes cerium, dysprosium, erbium, europium, among others) and phosphorus (chemical symbol P), which is associated with lunar maria. KREEP was first identified with NASA’s crewed Apollo missions to the lunar surface and is associated with maria and therefore volcanic and other geologic activity. According to this study, in addition to heating caused by radioactive decay from unstable elements, KREEP-enriched material on the lunar surface has lower melting points. This only added to expected geologic changes. The combined results of this study suggest that KREEP-enriched maria have been changing the lunar landscape since the rocky satellite was first formed billions of years ago.“
Read the whole story of Space.com or read the full study on Nature Geoscience.
No matter how much we learn about it, the Moon remains a fascinating mystery still…
And that’s one of the reasons we keep looking at it 🙂
Yes…and imagine when Artemis mission will be on its way