No matter where you are on Earth, you can only see one face of the moon, and that face looks very different from the one it hides from us on its far side.
Lunar seas (large and dark basaltic plains) dominate the near side of the moon, and these seas are vast, dark-colored remnants of ancient lava flows, RT reported.
While the far side is full of impact craters and is virtually devoid of the features of extensive lunar seas. The reason for this huge difference between the far and near sides of the moon has been one of the most enigmatic mysteries on the moon, since the first spacecraft orbited the moon in the 1960s.
And now, it seems that scientists have come up with a new explanation for the two-faced moon, an explanation related to a giant impact billions of years ago near the south pole of the moon.
A new study published in the journal Science Advances showed that the impact that formed the giant South Pole Aitken Basin (SPA), would have created a massive heat column spreading across the moon’s interior.
This plume would have carried certain materials, a combination of rare earth and heat-producing elements, to the near side of the moon, and this concentration of elements may have contributed to the volcanic activity that led to the creation of the nearby volcanic plains.
Dr Matt Jones at Brown University and lead author of the study said: ‘We know that large impacts like the one that formed the Aitken Basin would create a lot of heat.
The question is how does this temperature affect the internal dynamics of the moon? And what we’re showing is that under whatever reasonable conditions at the time of the formation of the Aitken Basin in Antarctica, it ends up concentrating these heat-producing elements on the near side.
We expect that this contributed to the melting of the mantle, which resulted in the lava flows we see on the surface.” Scientists first discovered the differences between the near and far sides of the moon in the 1960s through the Soviet Luna missions and the American Apollo program, while the differences in volcanic deposits are clearly visible. However, future missions will reveal differences in the geochemical composition as well.
The near side is home to a structural anomaly known as KREEP storms, or PKT, which stands for a concentration of potassium (K), rare earth elements (REE), and phosphorous (P), along with heat-producing elements such as thorium.
KREEP appears to be concentrated in and around the Oceanus Procellarum, the largest of the nearby volcanic plains, but is rare elsewhere on the Moon.
Some scientists suspect a link between PKT and nearby lava flows, but the question of why the group of elements is concentrated on the near side remains, and this new study provides an explanation related to the Antarctic-Aitken Basin, the second largest known impact crater in the solar system.
The scientists ran computer simulations of how the heat from a giant impact would change the convection patterns in the moon’s interior, and how this might redistribute KREEP material in the lunar mantle.
KREEP is believed to represent the last portion of the mantle that freezes after the moon’s formation. As such, it likely formed the outermost layer of the mantle, just below the lunar crust.
Models of the moon’s interior suggest that it should have been more or less evenly distributed under the surface. But this new model shows that the uniform distribution will be disrupted by the heat column from the Aitken Basin effect.
According to the model, the KREEP material would have traversed the heat wave from the Aitken Basin impact area like a surfer. As the heat plume spreads under the moon’s crust, this material was eventually delivered en masse to the near side, and the team simulated a number of different impact scenarios, from knockout to lightning strike.
While each produced different temperature patterns and mobilized KREEP to varying degrees, all created KREEP concentrations on the proximal side, consistent with the Aitken Basin anomaly. The researchers say the work provides a reliable explanation for one of the moon’s most enduring mysteries.
Dr Jones explained: “How the Aitken Basin formed is the most important open question in lunar science, and the impact of the South Pole-Aitken is one of the most important events in the history of the Moon, and this work brings those two things together, and I think our results are really exciting.”