Earth's Gravity Bathes the Moon's Core in Water
The latest models of the moon show that it may have a liquid blanketing its core.
We’ve solved may interesting mysteries about the moon over the decades. We know it was probably created by a mars-sized planet that slammed into the young earth. We know much about its once hidden “dark” side. We know it’s not made of cheese. Some mysteries have been hanging out for a while with no clear indication as to what’s going on. This includes some subtle but weird anomalies having to do with its orbit, rotation, and gravitation.
Gravitational assessments that have been done of the moon point to slightly different rotation rates depending on where inside the moon you’re looking. This points to the possibility that the interior of the moon has a liquidy center and some of the moon’s seismic data tends to support this theory. This support was never solid (so to speak) and other scientists using the same data disagreed, believing the moon was solid through and through.
Recently however, scientists from the US, China, and Japan, created a new and better model that, among other things, took into account the gravitational interplay between the moon, the earth, and sun. When the hit the GO button the moon’s gravitational field in the model matched the observations we’ve been seeing on the moon. When a model behaves like reality, it always make scientists happy. This is the strongest indication yet that the moon has some low viscosity water-like liquid between its mantle and core.
Of course this raised another mystery. Why is there liquid near its core? The prevailing theory now is that it might be due to tidal heating. Tidal heating is cool. The fall-off in the intensity of earth’s gravity kneads the moon like dough, creating friction which creates heat. We see dramatic examples of this on some moons of Jupiter and Saturn. This heat could also be responsible for much of the life that may exist in the universe (and perhaps our solar system). Life based on photosynthesis cannot exist when there’s a mile of ice or rock on top of you. Chemosynthetic life however doesn’t need light; all it really needs is some key elements and water created from the heat induced by tidal friction. There’s even chemosynthetic organisms at the bottom of our oceans. Don’t expect the moon to harbor such organisms though…we’d never be that lucky.
How though could any liquid persist for billions of years in that environment? The moon should have cooled enough over that time. Tidal heating may provide at least a partial reason why this is so. This liquid center could also help elucidate more fully the origins and evolution of the moon.