Recently, Earth has surprised scientists by revealing that its inside is actually a textured sphere that occasionally stops spinning and rotates the other way.
The Moon’s interior, however, remains a much greater mystery. The Moon’s mantle rests on top of what scientists believe to be a partially molten layer beneath its cratered crust, which may provide information about the Moon’s creation.
But a recent study suggests that there might not actually be an oozy layer.
Future data will determine whether new modeling by scientists from Germany, the Czech Republic, and the US is accurate. If so, the lunar mantle may not contain a melt-bearing layer as currently theorized and instead be entirely solid.
Future discoveries could either reset or reinforce our understanding of the Moon’s inner realms and how they arose, depending on which concept of the lunar interior is right.
Based on the few geological information we currently have, both a molten middle and a solid middle are still possibilities for the Moon. The experts behind this most recent study claim that additional lunar samples are required to unravel this riddle.
Planetary scientist Michaela Walterová of the German Aerospace Center in Berlin and colleagues made an effort to solidify our understanding of the Moon’s interior based on available data, accepted hypotheses, and a few novel concepts.
They evaluated two distinct lunar interior models to see which one most accurately accounted for the measurements we know of the Moon’s velocity and form.
Our lunar buddy travels 384,400 kilometers (238,855 miles) around the planet on average. From there, it pulls on Earth, shifting the tidal patterns in our oceans and atmosphere.
The density, viscosity, and rigidity of the Moon’s interior have a significant impact on these tidal effects. But because gravity acts in both directions, the Moon occasionally deforms.
Scientists might speculate about the composition of the Moon’s interior by observing these periodic cycles and utilizing lunar laser range to measure the Moon’s exact shape and velocity. Two possibilities stand to reason.
In their recently-published study, Walterová and colleagues write, “According to the first one, the lunar interior is hot and a small part of it might have melted, forming a thick layer of weak material buried more than 1,000 kilometers deep beneath the lunar surface.”
This model was developed as geoscientists worked to explain puzzling data obtained from a collection of lunar seismic stations used by the Apollo missions between 1972 and 1977.
They believed that a partially melted, viscous layer at the Moon’s core-mantle boundary provided the best explanation for their results when combined with additional seismological information on the tidal effects of the Moon.
They reasoned that this molten layer may disperse seismic waves and tidal energy in a way that matched periodic patterns in the data.
However, the results of a new investigation by Walterová and colleagues imply that there may be another cause.
“According to the second one, there is no such [molten] layer, and the measured deformation [of the Moon] can be explained by the behavior of solid rocks at relatively low temperatures,” the researchers write.
The two alternatives, however, “cannot be distinguished from each other” with the data at hand. So, if future lunar explorations are approved, we’ll have to wait to see what they reveal.
While there are still many unanswered issues, for the time being at least we have a better picture of what might be hidden behind the crusty lunar neighbor.
The study has been published in JGR Planets.
