Moon’s inner core revealed as solid iron: New study challenges old views

Scientists have made a significant discovery regarding the interior of the Moon. Research indicates that the inner core of our natural satellite is a solid sphere with a density similar to that of iron, confirming earlier assumptions.

Researchers have long studied the structure of the Moon's interior. Their findings now challenge traditional views on the evolution of the Moon's magnetic field. By demonstrating the existence of an inner core, they support the theory of a global mantle overturn and provide crucial insights into the Moon's bombardment timeline during the first billion years of the Solar System.

Studies into the internal composition of objects in the Solar System are most effective when using seismic data. Scientists utilize information on how acoustic waves, generated by earthquakes, move and reflect off matter inside a planet or satellite. Thanks to such data, they can create detailed maps of the interiors of these bodies.

As reported on ScienceAlert, we have seismic data from the Apollo missions, but its resolution is quite low. We know that the Moon's outer core is liquid. However, there were ongoing discussions about what surrounds it.

To resolve these uncertainties, Arthur Briaud from the French National Center for Scientific Research gathered data from space missions and laser-ranging experiments of the Moon to create a profile of various lunar features. These include the degree of deformation of our satellite due to its gravitational interaction with Earth, the variability of its distance from Earth, and its density. The next step was to conduct modeling with different types of cores to find the best match with the observations.

The findings suggest that models describing active overturn deep in the lunar mantle closely resemble the actual state. This indicates that denser material inside the Moon sinks toward the center, while less dense material rises.

The researchers' results indicate that the Moon's core resembles Earth's, with an outer liquid layer and a solid inner core. They assert that the radius of the outer core is about 225 miles, and the inner core is about 160 miles, roughly 15 percent of the Moon's radius. The density of the inner core is reported to be approximately 490 pounds per cubic foot.

In 2011, research led by NASA scientist Renee Weber reached similar conclusions, finding that the inner core has a radius of 149 miles and a density of about 500 pounds per cubic foot. According to Briaud and his team, these findings significantly enhance our understanding of the Moon's evolution.