The Moon's heart revealed for the first time

The Moon's heart revealed for the first time
by Staff Writers
Paris, France (SPX) May 05, 2023

Half a century after Apollo 11 initiated the first lunar surveys, a collaborative team of scientists from CNRS, University of the Cote d'Azur, Cote d'Azur Observatory, Sorbonne University, and Paris Observatory-PSL has unveiled a previously unknown aspect of the Moon's internal structure: a solid core akin to Earth's. Alongside this groundbreaking discovery, the researchers also provide evidence explaining the presence of iron-rich materials within the lunar crust. Their findings were published in Nature on May 3, 2023.

While the formation and evolution of the Moon continue to be debated, its deep interior structure has now been established. Over fifty years since humanity's first lunar missions, it is now undeniable that the Moon has a solid inner core encircled by a fluid outer core, much like Earth. This hypothesis has been confirmed through the efforts of scientists from CNRS, University of the Cote d'Azur, Cote d'Azur Observatory, Sorbonne University, and Paris Observatory-PSL.

Approximately two decades after the fluid outer core's identification, the team has uncovered the presence of a solid inner core with a diameter of around 500 km, comprising roughly 15% of the Moon's total size. This inner core is composed of a metal with a density similar to iron. Previously, the fluid outer core was identified through methods related to the Moon's rotation. However, the solid core remained elusive due to its small size. The researchers have now confirmed its existence using data from various space missions and lunar laser ranging.

In addition to this significant discovery, the team has found evidence supporting the lunar mantle overturn hypothesis, which suggests that material movement occurred within the mantle, the layer between the core and crust, during the Moon's evolution. This phenomenon helps explain the presence of iron-rich elements on the lunar surface. The process may have involved material rising to the surface, forming volcanic rocks that were then deposited in the lunar crust. Subsequently, materials denser than the surrounding crustal material sank back down to the core-mantle boundary.

This research offers valuable insights into the history of the solar system and events such as the disappearance of the lunar magnetic field, which was originally a hundred times stronger than Earth's present magnetic field but has since become almost non-existent.