Fig. 1
a: Snapshots of a head-on collision (impact velocity, 5 km s\(^{-1}\)) between 100 and 400 km diameter planetesimals composed of dunite. The initial porosities of the 100 and 400 km planetesimals are 0.4 and 0, respectively. From left to right, we show the collision after 0, 25, 50, and 75 s. Cylindrically symmetrical coordinates where the vertical (z) axis is the center of symmetry surrounded by the horizontal (r) axis are adopted. The color shows the volume fraction of the melt. The amount of melt reaches a maximum when \(t=75\) s, at which time the melt thickness is 10 km at the central axis. b: The amount of the mass of melt normalized by the impactor mass \(M_\textrm{melt}/M_\textrm{imp}\) as a function of the impact velocity with a fixed porosity of 0.4. If the impact velocity is faster than \(6\,\mathrm{km\,s}^{-1}\), the melt mass exceeds the mass of the impactor. c: The normalized amount of melt \(M_\textrm{melt}/M_\textrm{imp}\) as a function of impactor porosity with a fixed impact velocity of \(4\,\mathrm{km\,s^{-1}}\).
