Widespread Impact‐Induced Crustal Permeability on the Early Earth

The early Earth (i.e., Archean and Hadean Eons, 2.5–4.0 and 4.0–4.5 Ga, respectively) experienced frequent cosmic bombardment. Impacts have been shown to stimulate crustal alteration, for instance via hydrothermal systems active for up to millions of years post‐impact. Using a shock physics code that includes the effects of tensile fragmentation and porosity generation, we conduct the first comprehensive study to quantify impact‐generated permeable volumes into the upper crust of the early Earth for a suite of environmental (e.g., geothermal gradient, crustal thickness, presence of an ocean) and impact conditions (e.g., impactor velocity and size). Inferences from our suite of impact simulations suggest that the volume of impact‐induced permeable regions is strongly dependent on impact energy (i.e., impactor size and velocity). The range of generated permeability (10 −20 to 10 −12 m 2 ) within those regions, however, depends on the geothermal gradient and crustal composition. Moreover, we use a bombardment history model to infer the cumulative effects of recursive impacts onto the early Earth. We estimate that the upper 8 km shell of the Earth's crust may have been made highly permeable by impacts prior to 4.3 Ga, and that a significant portion of this volume would have been permeable until 3.5 Ga. These results show that impacts were instrumental in driving hydrothermal alteration of the early Earth's crust, with important consequences for the geochemical evolution of near‐surface environments.