Extended Data Figure 7. Chemical effect of equilibration of the impactor’s core in Earth’s magma ocean.

Another companion to Fig. 2, a plot showing the “swelling” of the impactor core to form the hybridized impactor core (HIC). The HIC is larger than the impactor core because of the dissolved mantle components therein, which can represent up to two times its initial mass. This y-axis shows the “swelling” factor, e.g. the ratio of HIC to impactor core $\left(Swelling=\frac{M_{Hybridized\hspace{0.17em}Impactor\hspace{0.17em}Core}}{M_{Impactor\hspace{0.17em}Core}}\right)$. This is equivalent to an effective dilution ratio. Small impactors interact with larger relative fractions of the magma ocean; therefore they incorporate more mantle components per unit mass than large impactors, and “swell” more. The HIC of a “fast-spinning” impactor²⁰ (2.5% Earth mass) is 2.2 times larger that the original impactor core, with 45% of its mass made of initial impactor core material (iron) and the remaining 55% consisting of magma ocean components, as shown in Fig. 2a. On the other hand, the core of a Mars-sized impactor¹⁹ (10% Earth mass) is 60% larger after equilibration with the magma ocean.