Even though it is widely accepted that the Moon formed by a large impact, it is still not clear if this hypothesis can be reconciled with the observed geochemical constraints. For instance, previous work suggests that the Moon would have lost a significant amount of water because the impact would have been so energetic that all the lunar water was lost to space. This model, however, may contradict geochemical studies that suggest that the Moon retains a significant amount of water.
To understand the connection between the impact model and lunar water abundance, we first run impact simulations to determine the disk structure. Our calculations show that the disk temperature near the mid-plane is 4000-7000 K (Nakajima & Stevenson, 2014). We further determine the disk structure and find that water escape from the disk would have been inefficient, and therefore the impact model is consistent with a water-rich Moon (Nakajima & Stevenson, 2018, in rev). We are further investigating how water and volatiles evolve over time.