What is inside the moon?

 It's Official : Scientists have confirmed what is inside the moon 

The Moon is not made of green cheese after all. A full investigation revealed that the Moon's inner core is, in fact, a "hard ball" with a density similar to that of iron. This, the researchers hope, will help resolve a long-standing debate over whether the Moon's core is solid or molten, and lead to a more accurate understanding of the history of our satellite, and by extension, that of the Solar System. "Our results," wrote a team led by astronomer Arthur Briaud of the French National Centre for Scientific Research in France, "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."

It is known that the investigation of the internal composition of objects in the Solar System is carried out more effectively through seismic data. The way acoustic waves generated by quakes move through and reflect from material inside a planet or moon can help scientists create a detailed map of the object's interior. There is lunar seismic data collected by the Apollo missions, but its resolution is too low to accurately determine the state of the inner core. A liquid outer core is known to exist, but what comprises the core is unknown. Models of a solid inner core and an entirely fluid core work equally well with the Apollo data.

To figure it out once and for all, Briaud and his colleagues gathered data from space missions and lunar laser beam experiments to compile a profile of various lunar features. These include the degree of its deformation by its gravitational interaction with Earth, the variation in its distance from Earth and its density. Next, they ran simulations with different nuclear types to find which best matched the observational data. As reported, they made several interesting findings. Firstly, the models that most closely resembled what we know about the Moon describe active overturn deep inside the lunar mantle. This means that denser material inside the Moon falls towards the centre, and less dense material rises upwards. This activity has long been proposed as a way to explain the presence of certain elements in the Moon's volcanic regions. The team's research adds another point in the "for" tally of evidence.

And they found that the lunar core is very similar to Earth's, with a liquid outer layer and a solid inner core. According to their modelling, the outer core has a radius of about 362 km's(225 miles) and the inner core has a radius of about 258 km's(160 miles). That's about 15 % of the entire radius of the Moon.  The inner core, the team found, also has a density of about 7,822 kg's per cubic meter. That's very close to the density of iron. Curiously, in 2011 a team led by NASA Marshall planetary scientist Renee Weber found a similar result using what were then state-of-the-art seismological techniques on Apollo data to study the lunar core.  They found evidence of a solid inner core with a radius of about 240 km's, and a density of about 8,000 kg's per cubic meter.

Their results, Briaud and his team say, are confirmation of those earlier findings, and constitute a pretty strong case for an Earth-like lunar core. And this has some interesting implications for the evolution of the Moon. We know that not long after it formed, the Moon had a powerful magnetic field, which started to decline about 3.2 billion years ago. Such a magnetic field is created by motion and convection in the core, so what the lunar core is made of is deeply relevant to how and why the magnetic field disappeared. Given humanity's hope to return to the Moon in relatively short order, perhaps we won't have long to wait for seismic verification of these findings.