Abstract
North Pole Dome (Pilbara Craton, Western Australia) contains unique geological analogs to early Earth and Mars. Recently discovered shatter cones in 3.47-billion-year-old (Ga) rocks reveal that it is also the site of an ancient meteorite impact. Initial reports claimed that the impact occurred at 3.47 Ga and produced a ≥100-kilometer (km) crater; we show that these age and size estimates are inaccurate. Shatter cones are radially oriented over a 6.5-km-diameter area, defining a 16-km-wide structure. Shatter cones postdate regional structures and occur in younger overlying rocks, providing unambiguous evidence that the impact occurred after ~2.7 Ga. We also report the first shocked mineral from this site, the high-pressure TiO(2) polymorph TiO(2)-II (srilankite). We provisionally name this feature the Miralga impact structure. The 3.47 Ga hydrothermally altered basalts at Miralga are the oldest known shocked terrestrial rocks, highlighting the site's analog potential for impacts into biosignature-bearing Archean greenstones and the Martian surface.