A groundbreaking study by Sander Goossens and colleagues has shed new light on the internal structure of the Moon. Using data from NASA’s GRAIL mission and the Lunar Reconnaissance Orbiter, the researchers have discovered evidence of a partially molten layer at the base of the Moon’s mantle, sandwiched between the solid mantle and the core. This discovery, published in AGU Advances, could have significant implications for our understanding of the Moon’s origin, evolution, and even potential future exploration efforts.
Tidal Hints Reveal the Moon’s Secrets
This discovery was directly tied to the study of tides on the Moon. For instance, the Moon itself is not a perfect sphere due to the gravitational pull of Earth and the Sun — people are most familiar with this effect as the cause for Earth’s oceanic tides. The shape and gravity field strength of our natural satellite also experiences its own forces based upon the tides. The researchers studied variations in the Moon’s gravity over both monthly and yearly cycles and managed to resolve numerous details of the internal structure of the Moon.
Whereas the monthly changes in the Moon’s gravity have been studied before, this is the first research to consider its annual variations too. The researchers used these measurements along with the average density of the Moon to build a holistic view of the interior of the Moon.
A Partially Molten Mantle Layer: Implications for the Moon’s Origin and Evolution
Hess’s and Parmentier’s work is the first to provide direct evidence of a partially molten layer at the core-mantle boundary in the Moon. The researchers found that by not treating this soft fluid-like layer in their model, they could not capture the gravity measurements that had been observed. Rather, this implies that it is an important part of the Moon’s deep interior structure.
The researchers propose that this layer may be comprised of a titanium-rich material such as ilmenite, but the composition would need further follow up work to completely explain and where the heat is coming from (over billions of year) to keep those melts pooled. This transition zone between the solid mantle and the core is likely to be important for our overall understanding of how the Moon formed and evolved.
Revealing the Mysteries of the Moon: Prospects for Future Exploration
The discovery of half-molten layer within the mantle of the Moon presents opportunities for further investigations that can be carried out in future. Knowing the Moon’s mantle can tell us a great deal about its thermal history and how it has been altered since it formed.
Future Space missions aimed at understanding the lunar mantle and additional studies on Earth could also work towards a better grasp of this layer as well as what consequence this may have for the composition and evolution of the Moon. While we further investigate into our near celestial neighbor, this new discovery is a step in the right direction to unlocking the future mysteries of the Moon.
