tokens: we cannot predict how the vapour production mass will scale with impact energy for very energetic giant impacts. Although the amount of mass in vapour is relatively independent of b and μ there is a strong dependence on these parameters when determining which body (target or projectile) the vapour comes from (Fig. 3 ). As expected for equal mass impacts, the vapour mass is produced equally from both the target and projectile, which is true for all impact angles (parameter b ). However, as μ decreases, the fraction of vapour production from the projectile is higher than that of the target. This behaviour is also sensitive to the impact angles as shown in Fig. 3 . Figure 3. The difference between the escaping vapour mass from the projectile normalized by projectile mass and the escaping vapour mass from the target normalized by the target mass versus the specific energy of the collision normalized by the catastrophic disruption criteria. Symbols and colour bar are same as in Fig. 2 . 3.2 Initial vapour velocity distribution Planetary embryo impacts produce a variety of post-collision dust distributions, none are isotropic as has been assumed in previous work (e.g. Jackson Wyatt 2012 ; Jackson et al. 2014 ; Wyatt et al. 2017 ). To be able to compare different distributions, we need to characterize the anisotropic nature of the collisionally generated dust. We separate the velocity of each escaping particle into two velocity components, the velocity parallel ( v ∥ ) and perpendicular ( v ⊥ ) to the direction of the impact. For example, the direction of the impact is the same (along the x -axis) for the two collisions shown in Fig. 1 . To understand and compare different distributions of particles, we choose to take the range between the 16 per cent and 84 per cent percentiles to compute the velocity dispersion for both velocity components in each collision (Δ v ∥ and Δ v ⊥ ). This allows us to compare the velocity distribution of different distributions without assuming a given distribution for any collision. We choose to take the 16 per cent and 84 per cent percentiles as this would be comparable to taking the 1σ values either side of the mean of a normal distribution. In Fig. 4 , we show the absolute velocity distributions of vapour condensates parallel (blue) and perpendicular (orange) to the direction of the collision and absolute velocity (black) for three different giant impacts. Fig. 4(a) shows sim. 168, a collision between 1.11 and 0.1 at 15 and b = 0.4. We choose to show sim. 168 as it is the closest simulated impact we have to the Moon-forming impact. Comparing to fig. 1 of Jackson Wyatt ( 2012 ), we have an overall similar distribution of absolute velocities and we find only a small difference between the direction vapour condensates are launched (close to isotropic). Fig. 4(b) shows sim. 8, a collision between two 0.1 at 10 and b = 0. Fig. 4(c) shows sim 88, a collision between two 0.1 at 10 and b = 0.8. There is a stark difference
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula O O O O O O O O O O O O O B-Formula I-Formula I-Formula O O O O O