The debate of whether the moon’s inner core is solid or molten has finally been settled by a team of scientists at the French National Centre for Scientific Research. According to the article published in the journal Nature in May last year, the inner heart of the moon is a solid ball and has an iron-like density.
“Our results,” the team led by astronomer Arthur Briaud wrote, “question the evolution of the Moon magnetic field thanks to its demonstration of the existence of the inner core and support a global mantle overturn scenario that brings substantial insights on the timeline of the lunar bombardment in the first billion years of the Solar System.”
Seismic information can be used to investigate the interior composition of celestial objects in the solar system. Scientists created a detailed chart of the moon’s interior by understanding how acoustic waves created by quakes pass through and reflect from the material inside.
Although the Apollo mission has provided seismic data from the moon, its low resolution makes it hard to make accurate deductions. While it is known that the outer core comprises a fluid, however, what lies beneath it remained a debate for a long time as the models of both a solid and liquid core work well with the data from Apollo.
Briaud and his team members collected data from various space missions and laser-ranging experiments on the moon to determine lunar characteristics and compared the data to various types of cores to find out which was the closest match.
The lunar models suggested that denser material remains towards the centre, while less dense material rises above. This also explains the elements found near the volcanic regions on the moon.
It was found that the moon’s core has a fluid outer layer and a solid inner core, which is similar to Earth’s. The model revealed that the outer core radius is about 362 kilometres (225 miles), and the inner core radius of around 258 kilometres (160 miles), making up 15 per cent of the entire radius of the moon.
The team was also able to determine the density of the moon to be about 7,822 kilograms per cubic meter, which is similar to the density of iron.
Interestingly, in 2011 a team led by NASA Marshall planetary scientist Renee Weber came to similar results from their investigation, which Briaud says are confirmed by his team’s findings that the lunar core is similar to Earth’s core.
Understanding the lunar core’s composition will help in understanding how and why the moon’s magnetic field began declining about 3.2 billion years ago, which used to be powerful in its initial stages, as this usually happens due to motion and convection inside the core.
(With inputs from agencies)