Production of sulphate-rich vapour during the Chicxulub impact and implications for ocean acidification

Journal name:
Nature Geoscience
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The mass extinction event at the Cretaceous/Palaeogene boundary 65.5 Myr ago has been widely attributed to the Chicxulub impact1, 2, but the mechanisms of extinction remain debated1, 3, 4, 5, 6. In the oceans, near-surface planktonic foraminifera suffered severe declines, in contrast to the relatively high survival rates of bottom-dwelling benthic foraminifera7. The vapour produced by an impact into Chicxulub’s target rocks, which include sulphate-rich anhydrite, could have led to global acid rain, which can explain the pattern of oceanic extinctions4, 5. However, it has been suggested that most of the sulphur in the target rocks would have been released as sulphur dioxide and would have stayed in the stratosphere for a long time6. Here we show, from impact experiments into anhydrite at velocities exceeding 10 km s−1, that sulphur trioxide dominates over sulphur dioxide in the resulting vapour cloud. Our experiments suggest that the Chicxulub impact released a huge quantity of sulphur trioxide into the atmosphere, where it would have rapidly combined with water vapour to form sulphuric acid aerosol particles. We also find, using a theoretical model of aerosol coagulation following the Chicxulub impact, that larger silicate particles ejected during the impact efficiently scavenge sulphuric acid aerosol particles and deliver the sulphuric acid to the surface within a few days. The rapid surface deposition of sulphuric acid would cause severe ocean acidification and account for preferential extinction of planktonic over benthic foraminifera.

At a glance


  1. Schematic diagram of the experimental set-up.
    Figure 1: Schematic diagram of the experimental set-up.

    A tantalum flyer and anhydrite target were placed in a large vacuum chamber. A laser-irradiated plastic ablator was attached to the front surface of the Ta flyer. The laser energy was absorbed by the ablator and the generated ablation plasma acted to accelerate the flyer. The chemical composition of the impact-induced vapour plume was measured directly using a quadrupole mass spectrometer (QMS). The vapour was introduced to the QMS using an inhalation tube. A hollow aluminium sphere was used to prevent the dispersal of the impact-induced gas.

  2. The SO3/SO2 ratios of impact-induced vapours as a function of impact velocities and peak shock pressures for impacts involving Murchison meteorite and anhydrite, obtained from the mass spectra of vapours using a QMS.
    Figure 2: The SO3/SO2 ratios of impact-induced vapours as a function of impact velocities and peak shock pressures for impacts involving Murchison meteorite and anhydrite, obtained from the mass spectra of vapours using a QMS.

    The data show that SO3 is the dominant sulphur oxide species in the impact vapours at impact velocities of a few tens of kilometres per second. The error bars are related to the sensitivity error of the QMS. Variance between the experiments is related to the adhesion of SOx gases to the wall of the vacuum system.

  3. Modelled temporal trends in the oceanic CO32- concentrations at a water depth of 60 m, following the impact.
    Figure 3: Modelled temporal trends in the oceanic CO32− concentrations at a water depth of 60 m, following the impact.

    The red curve shows CO32− concentrations calculated using the mass flux of sulphuric acid on the surface of the ocean. The green curve shows the CO32− concentrations in the case of dissolution equilibria processes between CO2 in the oceans and atmosphere. The dashed lines indicate the saturation levels of aragonite and calcite. The yellow shading indicates undersaturation of the ocean with respect to CaCO3.


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Author information


  1. Planetary Exploration Research Center, Chiba Institute of Technology, Chiba 275-0016, Japan

    • Sohsuke Ohno,
    • Kosuke Kurosawa,
    • Takafumi Matsui &
    • Seiji Sugita
  2. University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan

    • Toshihiko Kadono
  3. Department of Complexity Science and Engineering, University of Tokyo, Kashiwa 277-8561, Japan

    • Taiga Hamura &
    • Seiji Sugita
  4. Department of Earth and Space Science, Graduate School of Science, Osaka University, Osaka 560-0043, Japan

    • Tatsuhiro Sakaiya
  5. Institute of Laser Engineering, Osaka University, Osaka 565-0871, Japan

    • Keisuke Shigemori,
    • Yoichiro Hironaka,
    • Takayoshi Sano &
    • Takeshi Watari
  6. Institut national de la recherche scientifique—Énergie Matériaux Télécommunications, Varennes J3X 1S2, Canada

    • Kazuto Otani


S.O., T.K., T.M. and S.S. conceived the study and wrote the paper. S.O., T.K., K.K., T.H., T. Sakaiya, K.S., Y.H., T. Sano, T.W., K.O. and S.S. carried out the experimental work using the GXII and analysed the results. S.O. and S.S. created the sweeping out model and carried out the calculations.

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