The moon mantle: new discovery
New evidence confirms the formation of the lunar mantle and the asymmetric distribution of ilmenite cumulates, revealing details about the geological history of the Moon.
New evidence has confirmed theories about the formation of the lunar mantle, providing more details on the timing of this crucial event for the Moon. During the moon mantle's formation process, important insights into the chemical diversity between the near and far sides of the Moon emerged, with particular attention to the presence of seas on only one of the two sides. The Moon, like the Earth, is believed to be composed of a core, a mantle, and a crust, but the lunar mantle solidified long ago, making lunar geology simpler but equally fascinating and complex to study than the Earth's geology.
The standard theory of the formation of the lunar crust suggests that ilmenite-rich rocks formed from the sea of magma that covered the Moon early in its existence, resulting from the impact that gave rise to our satellite. These rocks, heavier than the liquid mantle below, sank into the mantle in a process known as global overturning. This phenomenon led to the formation of cumulates containing ilmenite on the lunar surface, visible to the astronauts of the Apollo missions.
However, the uneven distribution of these cumulates has raised questions about the exact sequence of events during this critical phase of lunar history. Scientists have identified a concentration of cumulates containing ilmenite in the PKT region, rich in potassium and rare earths, on the side of the Moon facing Earth. This has led to debates about their origin and why they are found mainly on one side of the satellite.
Gravitational anomalies around the PKT region are considered to be the remnants of the last stage of the lunar mantle rollover. Scientists have identified a correspondence between these anomalies and theoretical models of mantle overturning, suggesting that the event may have occurred around 4.09 billion years ago. The South Pole-Aitken impact, which occurred approximately 4.25 billion years ago, is hypothesized to have played a significant role in the overturning process.
The distribution of ilmenite-bearing cumulates and the estimated ages of the major lunar basins indicate that the overturning may have occurred at least 130 million years before the South Pole-Aitken impact. These results provide a clearer view of the Moon's geological history, revealing details hidden beneath its surface and confirming the consistency between theoretical models and observational data.
The study, published in Nature Geoscience (https://doi.org/10.1038/s41561-024-01408-2), represents an important step forward in understanding lunar evolution and opens new perspectives for further research on our fascinating astral companion.
