From impact to extinction to recovery: Discoveries of IODP-ICDP Expedition 364 to the Chicxulub impact structure

In 2016, International Ocean Discovery Program Expedition 364, with support from the International Continental Scientific Drilling Program, drilled into the peak ring of the Chicxulub impact structure, famous for its causal link to the mass extinction at the end of the Cretaceous. In this summary paper, we discuss key findings from Site M0077 on the cratering processes, marine ecosystem recovery after the mass extinction, and the post-impact hydrothermal system and habitability of the impact structure. Important results include (1) the confirmation of the dynamic collapse model of peak ring formation, (2) insights into impactite emplacement processes on Earth, where water is a key component, (3) discovery of the iridium anomaly within the impact basin, unequivocally linking the Chicxulub impact basin to the global Cretaceous-Paleogene (K-Pg) boundary layer, (4) evidence for key atmospheric inputs of dust, sulfate aerosols, and soot, all likely contributing to global cooling and reduction of photosynthesis as drivers for extinction, (5) rapid recovery of life within the ocean overlying the crater, including a primary succession driven by in part by picoplankton before a transition over 100 s kyr to diversifying planktic communities, and (6) the presence of a long-lived hydrothermal system with extant thermophilic life in the buried peak ring 66 Myr later. The Chicxulub crater represents exceptional scientific opportunity in that it bridges planetary science, impact dynamics, and astrobiology; the integration of such findings continue to reveal the transformative power of asteroid impacts as a major geologic and biologic process. • Summary of major results and next research steps from the IODP-ICDP scientific drilling expedition to the Chicxulub impact structure • Dynamic collapse model of peak ring impact basin formation validated • Crater filled with impact melt rock and melt-bearing breccia (suevite) and underwent ocean resurge • Chicxulub unequivocably linked to Cretaceous-Paleogene mass extinction containing the global iridium layer and producing dust, sulfate aerosols, and soot • Recovery of life in crater is similar to global ocean with primary succession driven by picoplankton before transitioning over 100 s of kyr to plankton dominated communities • Chicxulub subsurface contained extant thermophilic biota and evidence for long-lived hydrothermal system