The Moon's Inner Core Revealed as Solid, Not Molten, in Groundbreaking Research

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Recent research has concluded that the moon's inner core is not molten but rather a solid sphere with a density similar to that of iron. Led by astronomers from the French National Centre for Scientific Research, the study utilised seismic data collected by Apollo missions and lunar laser ranging experiments, coupled with various space mission data. The team modelled the moon's internal composition, focusing on gravitational deformation, distance variation from Earth, and density.

The findings dismiss the long-standing debate over whether the moon's core is solid or molten. The models best aligned with known lunar characteristics suggested active overturning deep within the moon's mantle, where denser material falls towards the centre and less dense material rises. This process explains certain elements found in the moon's volcanic regions.

The study affirms a structure for the moon similar to Earth, featuring an outer fluid layer and a solid inner core. The outer core has a radius of approximately 362 kilometres, while the inner core is about 258 kilometres, constituting around 15 per cent of the moon's total radius. The inner core's density closely matches that of iron, at around 7,822 kilograms per cubic meter.

Interestingly, these findings align with a 2011 study by NASA Marshall planetary scientist Renee Weber, which used advanced seismological techniques on Apollo data. Weber's team had also identified a solid inner core with a radius of about 240 kilometres and a density of approximately 8,000 kilograms per cubic meter.

The research confirms previous findings and holds implications for the moon's evolution. The moon once had a strong magnetic field, which began to decline around 3.2 billion years ago. Understanding the composition of the lunar core is crucial in explaining the disappearance of the magnetic field and offers insights into the moon's history, which is relevant for future lunar exploration endeavours.