Permeability data for impact breccias imply focussed hydrothermal fluid flow

New measurements of permeability from 14 samples of impact breccia in meteorite impact craters all indicate values of 1 mD or lower. These values are low and suggest that fluid flow through impact craters, evidenced by hydrothermal systems in numerous craters, is predominantly through fracture systems. Mineral precipitation by circulating fluids would eventually seal the fractures. The focussing of hydrothermal fluid flow in fractures emphasizes their importance as potential sites for microbial colonization, and suggests that the sealing minerals are good targets to search for evidence of life.