We can always see only one side of the moon, no matter where in the world we are. The other side has always been far from our planet and this side has much more craters than the side we can see. Scientists now claim in a new study published in Science Advances that it has something to do with lava flows.
The side of the moon that we can see is covered in lunar maria, which are large areas of volcanic basalt that appear as dark spots when we look at a satellite. The reason for this mysterious appearance has remained a mystery since the first spacecraft flew into orbit around the Moon in the 1960s. But scientists say a new simulation may now have solved the mystery of the Apollo era.
Computer models put the different features together, supporting the idea that a massive impact on the Moon once appeared on the Moon’s face in lava flows. The differences are not only profound, but are also reflected in the different geological structures on both sides of the Moon.
SPA . collision
Astronomers have long suspected that the moon’s face was covered in a sea of magma that cooled and softened the rocky landscape, creating the dark spots we see today. But the cause of this volcanic activity is controversial. Scientists now say that a huge crater at the moon’s south pole, known as the South Pole-Aitken Basin (SPA), could explain the differences.
This basin is a remnant of one of the largest and oldest impacts on the moon’s surface. Simulations show that the SPA collision, which occurred about 4.3 billion years ago, occurred at exactly the right time and in the right place to cause changes to only one side of the moon’s mantle. The massive heat of the impact heated the upper part of the mantle near the side so much that scientists believe it led to a concentration of potassium, rare earth elements, phosphorous, and heat-producing elements such as thorium.
So far, this is exactly the formation that scientists have found in the lunar asbestos samples we can see, most notably in the Procellarum KREEP Terrane (PKT), a large area known for this compositional anomaly. “What we’re showing is that under all reasonable conditions at the time of SPA’s formation, it ultimately concentrates on these semi-heat-producing elements,” explains planetary scientist Matt Jones of Brown University. “We hypothesize that this may have contributed to the mantle melting, creating the lava flows we see at the surface.”
Hundreds of millions of years
The fallout from the SPA event is likely to last for hundreds of millions of years. In simulations, the oldest volcanic plain on the edge erupted 200 million years after the collision. In fact, intense episodes of volcanic activity continued on the far side of the Moon for 700 million years after the collision.
According to scientists, the reason for the interaction of this side of the Moon with the impact is explained by the two places where the impact is focused on the transport of heat-producing substances and the slight changes in gravity.
In each scenario the researchers looked at, the upper mantle in the southern hemisphere warmed and elements began to flow into the northern hemisphere through the near side. Meanwhile, the upper mantle has remained too cold to dissipate the same substance in a similar way. This difference may have caused a noticeable asymmetry between the two sides of the moon. “How PKT came into being is probably the most important open question in lunar science,” Jones said. The South Pole-Aitken effect is one of the most important events in the history of the Moon. This work combines these two things and I think our results are very exciting.”
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