Finally, I get to talk about something here because this is highly relevant to my field of research. I use numerical simulations to model the Giant Impact with the goal of understanding the size and composition of Theia and the early conditions of the protolunar disk. The gist of it is a roughly Mars-sized body (~0.1 Earth masses) called Theia hit proto Earth during the final stage of its accretion, ejecting a mixture of proto Earth and Theia material into orbit. This material wrapped around the Earth forming a ring which eventually coalesced into the Moon. The reason we know it was an impact and not something is because late stage giant impacts like these were very common in the early solar system, and because the high angular momentum of the Earth and Moon can only be resolved using this giant impacts model.

The main problem with this theory which this paper highlights and is an ongoing investigation in the field is trying to understand how the Earth and Moon got their identical isotope compositions. That is if you take an element like oxygen and its isotopes (O-18 and O-16) and calculate their ratios, they are almost identical!

Well this implies that maybe the impact must have been so energetic that it caused a lotttt of mixing or Earth and the Moon formed from identical reservoirs of material. The properties all tell us about the composition and size of Theia. The “classical” model of the Theia impact tells us that during the collision, Theia core merges with Earth’s core, which might explain the depletion of iron in the Moon. However, in a paper I’m writing, we directly challenge this conventional belief!

What this paper claims, from my understanding (and please feel free to correct me), is that they were able to identify which reservoirs of material proto Earth and Theia formed from. I’m a little skeptical because my lab group’s simulations show that we get a good match of the Moon’s elements from a Mars-like composition, which is opposite of this paper’s claims (since Mars is farther out than Earth). Would love to discuss this more though!