[Rockhounds] It's Official: Scientists Have Confirmed What's Inside Our Moon

[Kreigh Tomaszewski]

Well, the verdict is in. The Moon <https://www.sciencealert.com/moon> is
not made of green cheese
<https://en.wikipedia.org/wiki/The_Moon_is_made_of_green_cheese> after all.

A thorough investigation published in May 2023 found that the inner core of
the Moon is, in fact, a solid ball with a density similar to that of iron.
This, researchers hope, will help settle a long debate about whether the
Moon's inner heart is solid
<https://www.science.org/doi/abs/10.1126/science.1199375> or molten
<https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL082677>,
and lead to a more accurate understanding of the Moon's history – and, by
extension, that of the Solar System.

"Our results," wrote a team led by astronomer Arthur Briaud
<https://www.nature.com/articles/s41586-023-05935-7> 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."

Probing the interior composition of objects in the Solar System is most
effectively accomplished 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
<https://www.sciencealert.com/in-an-incredible-first-scientists-have-discovered-whats-at-the-core-of-mars>
.

We happen to have lunar seismic data collected by the Apollo mission, but
its resolution is too low to accurately determine the inner core's state. We
know there is a fluid outer core
<https://adsabs.harvard.edu/full/1981LPI....12.1043S>, but what it
encompasses remains under debate. 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 collected data
from space missions and lunar laser-ranging
<https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment> experiments
to compile a profile of various lunar characteristics. These include the
degree of its deformation by its gravitational interaction with Earth, the
variation in its distance from Earth, and its density.

https://www.sciencealert.com/its-official-scientists-have-confirmed-whats-inside-our-moon