Extended Data Fig. 8: Contrasting trajectory examples.

Trajectories like Extended Data Figure 7c for Basalt grains at average Mars conditions of size (a) d = 1 mm and (b) d = 10μm. The green lines are the ‘target’ restitution coefficient for each case using the empirical relation found in Extended Data Figure 4c. The qualitatively different behavior in the neighborhood of the solution shows how this formulation of the impact threshold loses meaning for small grains. The minima for each successive curve of fixed friction velocity in (a) are close and transition smoothly, and u_* and v_↑ are not extremely different. This is in contrast with (b), where the minima close to the target restitution rapidly diverges as u_* changes, and v_↑ is extremely small at the minima relative to u_*.