The celestial body we see in the sky may not be the original Moon.
According to Science Alert, a new study led by planetary scientists Weigang Liang and Adrien Broquet from the University of Arizona (USA) suggests that the Moon’s mantle may have been flipped upside down in its strange past.
This event occurred around 4.22 billion years ago, a few hundred million years after the satellite known as the Moon coalesced from debris of early Earth and the planet Theia.
Illustration showing two flow accumulations containing ilmenite due to the Moon’s mantle being overturned – (Photo: UNIVERSITY OF ARIZONA).
Theia is a hypothetical celestial body the size of Mars that collided with Earth 4.5 billion years ago, merging to form present-day Earth.
Traces of the overturned mantle were discovered from anomalies in the KREEP Terrane region on the Moon, which is unexpectedly rich in potassium, rare earth elements, and phosphorus.
KREEP Terrane is also part of a vast basalt plain on the Moon, rich in minerals called ilmenite – composed of titanium and iron – which are quite dense like the rock that contains them.
When magma finishes cooling and crystallizing, dense minerals should gradually sink toward the planet’s core. If they are brought up a bit by volcanic activity, they should be evenly distributed across the celestial body.
In reality, today’s Moon has a very peculiar surface, chemically asymmetric. This presents another paradox. The Moon should resemble Earth more closely, as both were formed from early Earth and Theia.
Through analysis using various models, the research team ultimately determined that the unusual concentration of heavy elements in this region can only be explained by the Moon’s mantle being completely overturned after its formation.
This disruption flipped materials from the bottom of the mantle to the top in some areas, creating the observed anomalies.
Of course, the crust of a celestial body is also greatly influenced by mantle disruption in a harsh rock recycling process. Therefore, it can be said that the entire primordial Moon was deformed, differing significantly from the celestial body originally “born” from Earth and Theia.
