Impact events

Geology And Mars Analog Potential Of The < 2.7-billion-year-old Miralga Impact Structure, North Pole Dome, Pilbara Craton, Australia

By Keith Cowing

Press Release

Science Advances via PubMed

August 18, 2025

Filed under Biosignatures, crater, Extinction event, Impact event, Miralga Impact Structure, Mount Roe, Pilbara Craton, shatter cone

Geology And Mars Analog Potential Of The < 2.7-billion-year-old Miralga Impact Structure, North Pole Dome, Pilbara Craton, Australia — (A) Field photograph of exceptional shatter cones near the center of the structure. Photo credit: A.R.B./Harvard University. (B) Geologic map of the structure, which occupies the north flank of North Pole Dome. Red points indicate shatter cone outcrops, which occur within an ~6.47-km–diameter area (blue solid circle) centered on the inferred point of impact (blue square). An inferred total diameter of ~16.2 km for the structure (blue dashed circle) is calculated from scaling laws using the shatter cone occurrence diameter (37). The map data are modified from the GSWA (83) based on our mapping. (C) Context map showing the location within Australia and the Pilbara Craton. — Science Advances via PubMed

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 TiO2 polymorph TiO2-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.

White arrows indicate selected shatter cone apices and point in the direction of shock propagation. See table S1 for locations for each of the pictured shatter cones. Photo credit (all panels): A.R.B./Harvard University. (A) Shatter cones in weakly propylitic altered massive vesicular basalt of the 2.77 Ga Mount Roe Basalt. (B) Shatter cones in an intensely chloritized fault zone in the Mount Ada Basalt, likely dating to <2.71 Ga. The occurrence of shatter cones in the ~2.7 Ga units in (A) and (B) indicate a <2.7 Ga, postdeformation date for the impact. (C) Small shatter cones in ferruginous chert of the 3.47 Ga Antarctic Creek Member near the center of the structure. — Science Advances via PubMed

Geology and Mars analog potential of the <2.7-billion-year-old Miralga impact structure, North Pole Dome, Pilbara Craton, Australia, Science Advances via PubMed

Astrobiology, Astrogeology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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