(ORDO NEWS) — No matter where you are on Earth, you can only see one side of the Moon. Its other side is forever turned away from our planet, and it is much more cratered than the one that faces us.
The bright side of the Moon is covered in lunar seas, vast plains of volcanic basalt that look like dark spots when we look at our moon.
The reason for this two-faced appearance has remained a mystery that has persisted since the first spacecraft orbited the Moon in the 1960s. But a new simulation could solve the mystery of the Apollo era.
By piecing together various features, computer models support the idea that a massive lunar collision once surfaced on the near side of the Moon in lava flows.
The differences are more than profound as they are also reflected in the different geologic compositions on each side of the moon.
Astronomers have long suspected that the near side was once covered in a sea of magma that, as it cooled, flattened the rocky landscape, creating the dark patches we see today. But the cause of this volcanic activity is controversial.
A massive crater at the Moon’s south pole, known as the South Pole-Aitken Basin, may explain the differences.
This basin is the remnant of one of the largest and oldest collisions on the Moon. Simulations show that the SPA event, which occurred about 4.3 billion years ago, happened at just the right time and in the right place to initiate changes on just one side of the lunar mantle.
The massive amount of heat generated by the impact could have heated the upper mantle on the near side to the point that experts believe would have resulted in concentrations of potassium, rare earths, phosphorus, and heat-producing elements such as thorium.
In the simulation, the oldest nearby volcanic plain erupted 200 million years after the impact events. In fact, intense episodes of volcanic activity continued on the near side of the Moon until 700 million years after the impact.
The reason why this side of the moon reacted more strongly to the impact, experts say, is both where the transport of heat-producing materials was concentrated at the impact site and small changes in gravity.
In each scenario considered by the researchers, the upper mantle in the southern hemisphere heated up and began to flow towards the northern hemisphere, traveling along the near side.
Meanwhile, the upper mantle on the dark side remained too cold to distribute the same material in a similar fashion.
This difference could well have given rise to the asymmetry observed in the two faces of the Moon.
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