In a significant development for lunar science, researchers have confirmed that the Moon’s inner core is solid rather than molten. Published in May 2023, this investigation led by Arthur Briaud from the French National Centre for Scientific Research provides new insights into the Moon’s geological history and its evolutionary processes.
The study reveals that the Moon’s inner core is a solid entity with a density comparable to that of iron. This finding is pivotal in settling a longstanding debate regarding the composition of the Moon’s core and contributes to a deeper understanding of the Moon’s formation and its magnetic history.
Research Methodology and Findings
To arrive at their conclusions, Briaud and his team utilized data from various lunar missions and laser-ranging experiments. They examined a range of characteristics, including the Moon’s gravitational interactions with Earth, its distance variations, and its density. By modeling different core types, they determined that the most accurate representations align with an active overturn process within the Moon’s mantle.
The researchers discovered that denser materials within the Moon descend toward the center, while lighter materials rise. This dynamic mechanism may explain the distribution of certain elements found in the Moon’s volcanic regions, adding further weight to existing theories.
The modeling indicates that the lunar core has an outer fluid layer approximately 362 kilometers (about 225 miles) in radius and a solid inner core with a radius of about 258 kilometers (approximately 160 miles). This solid inner core constitutes around 15 percent of the Moon’s total radius, and its density measures around 7,822 kilograms per cubic meter, closely resembling that of iron.
Implications for Lunar Evolution
This research aligns with findings from a 2011 study conducted by Renee Weber at NASA Marshall, which similarly identified characteristics of a solid inner core. Weber’s team reported a radius of about 240 kilometers and a density near 8,000 kilograms per cubic meter. Briaud’s findings reinforce this earlier work, suggesting that the Moon’s core shares similarities with that of Earth.
The implications of these findings extend to understanding the Moon’s past magnetic field, which was significantly stronger shortly after its formation and began to decline approximately 3.2 billion years ago. The presence of a solid inner core is critical to understanding the mechanisms behind this decline, as the dynamism within the core is responsible for generating magnetic fields.
As humanity prepares for a potential return to the Moon in the near future, the possibility of seismic verification of these findings may soon materialize. The research has been published in the esteemed journal Nature, marking a notable milestone in lunar exploration and planetary science.
