Scientists think they've finally solved the mystery of what's inside the Moon

Seismic data is the most effective way to probe the interior composition of objects in the Solar System. Acoustic waves generated by quakes move through and reflect from the material inside a planet or moon, allowing scientists to determine its structure. 

NASA's Apollo missions in the 1960s and 1970s obtained seismic data that was too imprecise to accurately determine the inner core's state. Still, NASA has announced that they've found evidence for an iron-rich core under about 1,700 miles (2,700 kilometers) of silicate mantle rock, at least as deep as Earth's core—and possibly much deeper than that.

How was the information confirmed? 

Arthur Briaud and his colleagues collected data from space missions and lunar laser-ranging experiments. They then used this information to estimate the degree of deformation by its gravitational interaction with Earth, as well as the variation in its distance from Earth. 

The researchers also calculated an average density for each hemisphere based on measurements taken by NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, which involved two spacecraft orbiting around our satellite from 2011-2012.

The results of their investigation found that the inner core of the Moon is a solid ball with a density similar to that of iron. This discovery has led to a more accurate understanding of the Moon's history and the timeline of the lunar bombardment in the first billion years of our Solar System.

The discovery of the solid inner core has questioned the evolution of the Moon's magnetic field and supports a global mantle overturn scenario. This has implications for the Moon's structure, composition, and formation history. Scientists can now use the data to understand the Moon's structure, composition, and formation history.