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Impact spherules as a record of an ancient heavy bombardment of Earth


Impact craters are the most obvious indication of asteroid impacts, but craters on Earth are quickly obscured or destroyed by surface weathering and tectonic processes1. Earth’s impact history is inferred therefore either from estimates of the present-day impactor flux as determined by observations of near-Earth asteroids, or from the Moon’s incomplete impact chronology2,3,4. Asteroids hitting Earth typically vaporize a mass of target rock comparable to the projectile’s mass. As this vapour expands in a large plume or fireball, it cools and condenses into molten droplets called spherules5. For asteroids larger than about ten kilometres in diameter, these spherules are deposited in a global layer. Spherule layers preserved in the geologic record accordingly provide information about an impact even when the source crater cannot be found1. Here we report estimates of the sizes and impact velocities of the asteroids that created global spherule layers. The impact chronology from these spherule layers reveals that the impactor flux was significantly higher 3.5 billion years ago than it is now. This conclusion is consistent with a gradual decline of the impactor flux after the Late Heavy Bombardment.

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Figure 1: Earth’s impactor SFD.

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  1. Simonson, B. M. & Glass, B. P. Spherule layers—records of ancient impacts. Annu. Rev. Earth Planet. Sci. 32, 329–361 (2004)

    Article  CAS  ADS  Google Scholar 

  2. Ivanov, B. A. & Hartmann, W. K. In Treatise on Geophysics Vol. 10 Planets and Moons (ed. Schubert, G. ). 202–242 (Elsevier, 2007)

    Google Scholar 

  3. Le Feuvre, M. & Wieczorek, M. A. Nonuniform cratering of the Moon and a revised crater chronology of the inner Solar System. Icarus 214, 1–20 (2011)

    Article  ADS  Google Scholar 

  4. Stuart, J. S. & Binzel, R. P. Bias-corrected population, size distribution, and impact hazard for the near-Earth objects. Icarus 170, 295–311 (2004)

    Article  ADS  Google Scholar 

  5. Johnson, B. C. & Melosh, H. J. Formation of spherules in impact produced vapor plumes. Icarus 217, 416–430 (2012)

    Article  CAS  ADS  Google Scholar 

  6. Raizer, Y. P. Condensation of a cloud of vaporized matter expanding in vacuum. Sov. Phys. JETP 37, 1229–1235 (1960)

    Google Scholar 

  7. Melosh, H. J. & Vickery, A. M. Melt droplet formation in energetic impact events. Nature 350, 494–497 (1991)

    Article  ADS  Google Scholar 

  8. O’Keefe, J. D. & Ahrens, T. J. The interaction of the Cretaceous/Tertiary extinction bolide with the atmosphere, ocean, and solid Earth. Geol. Soc. Am. Spec. Pap. 190, 103–120 (1982)

    Google Scholar 

  9. Smit, J. The global stratigraphy of the Cretaceous-Tertiary boundary impact ejecta. Annu. Rev. Earth Planet. Sci. 27, 75–113 (1999)

    Article  CAS  ADS  Google Scholar 

  10. Alvarez, L. W., Alvarez, W., Asaro, F. & Michel, H. V. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science 208, 1095–1108 (1980)

    Article  CAS  ADS  Google Scholar 

  11. Collins, G. S., Melosh, H. J., Morgan, J. V. & Warner, M. R. Hydrocode simulations of Chicxulub crater collapse and peak-ring formation. Icarus 157, 24–33 (2002)

    Article  ADS  Google Scholar 

  12. Kyte, F. T., Shukolyukov, A., Lugmair, G. W., Lowe, D. R. & Byerly, G. R. Early Archean spherule beds: chromium isotopes confirm origin through multiple impacts of projectiles of carbonaceous chondrite type. Geology 31, 283–286 (2003)

    Article  CAS  ADS  Google Scholar 

  13. Lowe, D. R. et al. Spherule beds 3. 47–3. 24 billion years old in the Barberton Greenstone Belt, South Africa: a record of large meteorite impacts and their influence on early crustal and biological evolution. Astrobiology 3, 7–48 (2003)

    Article  ADS  Google Scholar 

  14. Yancey, T. E. & Guillemette, R. N. Carbonate accretionary lapilli in distal deposits of the Chicxulub impact event. Geol. Soc. Am. Bull. 120, 1105–1118 (2008)

    Article  CAS  ADS  Google Scholar 

  15. Minton, D. A. & Malhotra, R. Dynamical erosion of the asteroid belt and implication for large impacts in the inner Solar System. Icarus 207, 744–757 (2010)

    Article  ADS  Google Scholar 

  16. Lowe, D. R. & Byerly, G. R. Did LHB end not with a bang but a whimper? The geologic evidence. 41st Lunar Planet. Sci. Conf. 2563 (2010)

  17. Gomes, R., Levinson, H. F., Tsiganis, K. & Morbidelli, A. Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets. Nature 435, 466–469 (2005)

    Article  CAS  ADS  Google Scholar 

  18. Bottke, W. F. et al. An Archaean heavy bombardment from a destabilized extension of the asteroid belt. Nature (this issue).

  19. Rasmussen, B. & Koeberl, C. Iridium anomalies and shocked quartz in a Late Archean spherule layer from Pilbara craton: new evidence for a major asteroid impact at 2. 63 Ga. Geology 32, 1029–1032 (2004)

    Article  CAS  ADS  Google Scholar 

  20. Kohl, I., Simonson, B. M. & Berke, M. Diagenetic alteration of impact spherules in the Neoarchean Monteville layer, South Africa. Geol. Soc. Am. Spec. Pap. 405, 57–73 (2006)

    Google Scholar 

  21. Goderis, S. et al. Geochemical correlation of two late Archean impact spherule layers between South Africa and Western Australia: the Paraburdoo-Reivilo link. 43rd Lunar Planet. Sci. Conf. 1882 (2011)

  22. Hassler, S. W., Simonson, B. M., Sumner, D. Y. & Bodin, L. Paraburdoo spherule layer (Hamersley Basin, Western Australia): distal ejecta from the fourth large impact near the Archean-Proterozoic boundary. Geology 39, 307–310 (2011)

    Article  ADS  Google Scholar 

  23. Simonson, B. M. et al. Geochemistry of 2. 63–2. 49 Ga impact spherule layers and implications for stratigraphic correlations and impact processes. Precambr. Res. 175, 51–76 (2009)

    Article  CAS  ADS  Google Scholar 

  24. Simonson, B. M. Geological evidence for a strewn field of impact spherules in the early Precambrian Hamersley basin of Western Australia. Geol. Soc. Am. Bull. 104, 829–839 (1992)

    Article  ADS  Google Scholar 

  25. Glikson, A. & Allen, C. Iridium anomalies and fractionated siderophile element patterns in impact ejecta, Brockman Iron Formation, Hamersley basin, Western Australia: evidence for a major asteroid impact in simatic crustal regions of the early Proterozoic Earth. Earth Planet. Sci. Lett. 220, 247–264 (2004)

    Article  CAS  ADS  Google Scholar 

  26. Simonson, B. M., Sumner, D. Y., Beukes, N. J., Johnson, S. & Gutzmer, J. Correlating multiple Neoarchean-Paleoproterozoic impact spherule layers between South Africa and Western Australia. Precambr. Res. 169, 100–111 (2009)

    Article  CAS  ADS  Google Scholar 

  27. Chadwick, B., Claeys, P. & Simonson, B. New evidence for a large Palaeoproterozoic impact: spherules in a dolomite layer in the Ketilidian orogeny, South Greenland. J. Geol. Soc. Lond. 158, 331–340 (2001)

    Article  CAS  Google Scholar 

  28. Shukolyukov, A. & Lugmair, G. W. Isotopic evidence for the Cretaceous-Tertiary impactor and its type. Science 282, 927–930 (1998)

    Article  CAS  ADS  Google Scholar 

  29. Glass, B. P., Koeberl, C., Blum, J. D. & McHugh, M. G. Upper Eocene tektite and impact ejecta layer on the continental slope off New Jersey. Meteorit. Planet. Sci. 33, 229–241 (1998)

    Article  CAS  ADS  Google Scholar 

  30. Kyte, F. T., Shukolykov, A., Hildebrand, A. R., Lugmair, G. W. & Hanova, J. Chromium-isotopes in Late Eocene impact spherules indicate a likely asteroid belt provenance. Earth Planet. Sci. Lett. 302, 279–286 (2011)

    Article  CAS  ADS  Google Scholar 

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We thank B. Simonson and C. Chapman, whose comments improved this work. We acknowledge support from NASA.

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B.C.J. developed the methods used in this work with the guidance of H.J.M. Both authors contributed to the conclusions presented in this work.

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Correspondence to B. C. Johnson.

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The authors declare no competing financial interests.

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Johnson, B., Melosh, H. Impact spherules as a record of an ancient heavy bombardment of Earth. Nature 485, 75–77 (2012).

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