Time-resolved studies of hypervelocity vertical impacts into porous particulate targets: Effects of projectile density on early-time coupling and crater growth

► Experimental study of role of projectile density on impact coupling depth/location. ► Under-dense projectiles couple closer to the surface and quicker than denser impactors. ► Effects of early-stage coupling (evolving ejection angles) extend to main-stage growth. ► Metrics for the transient depth to diameter ratio demonstrate non-proportional growth. ► Results have implications for ballistic emplacement of ejecta on planetary surfaces.