From ScienceDaily:
Many theorists believe a Mars-sized object slammed into the early Earth, and material dislodged from that collision formed the basis of the moon. When this idea was tested in computer simulations, it turned out that the moon would be made primarily from the impacting object. Yet the opposite is true; we know from analyzing rocks brought back from Apollo missions that the moon consists mainly of material from Earth.
A new study published April 29 in Nature Geoscience, co-authored by Yale geophysicist Shun-ichiro Karato, offers an explanation.
The key, Karato says, is that the early, proto-Earth — about 50 million years after the formation of the Sun — was covered by a sea of hot magma, while the impacting object was likely made of solid material. Karato and his collaborators set out to test a new model, based on the collision of a proto-Earth covered with an ocean of magma and a solid impacting object.
The model showed that after the collision, the magma is heated much more than solids from the impacting object. The magma then expands in volume and goes into orbit to form the moon, the researchers say. This explains why there is much more Earth material in the moon’s makeup. Previous models did not account for the different degree of heating between the proto-Earth silicate and the impactor. Paper. paywall – Natsuki Hosono, Shun-ichiro Karato, Junichiro Makino, Takayuki R. Saitoh. Terrestrial magma ocean origin of the Moon. Nature Geoscience, April 29, 2019; DOI: 10.1038/s41561-019-0354-2 More.
According to the new theory, 80% of the Moon’s material is proto-Earth. Probably too hot to hope to find fossils there if life got started on Earth as soon as sme research suggests, but we’ll see.
Note: There are many theories of the Moon’s origin. See below items the vid.
Before you go: Hugh Ross: The fine-tuning that enabled our life-friendly moon creates discomfort Was it yesterday that we noted particle physicist Sabine Hossenfelder’s view that fine-tuning is “a waste of time”? Not so fast. If the evidence points to fine-tuning and the only alternative is the crackpot cosmology she deplores, it’s not so much a waste of time as a philosophically unacceptable conclusion. Put another way, it comes down to fine-tuning, nonsense, or nothing.
Moon formed from smashed moonlets?
Scientists finally know how old Moon is What’s surprising, really, is how little we know about the moon in general.
And various current theories:
Another moon origin theory: Epic crash
How the Moon Formed: 5 Wild Lunar Theories (Mike Wall at Space.com, 2014)
Our moon formed in collision with embryo planet?
and
Origin of the moon still shrouded in mystery
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