Masse, W.B., Weaver, R.P., Abbott, D.H., Gusiakov, V.K. and Bryant, E.A., 2012. Missing in action? Evaluating the putative absence of impacts by large asteroids and comets during the quaternary period. Proceedings of the Advanced Maui Optical and Space Surveillance Technologies Conference, pp. 701-710. Sept. 9-12. 2007. Wilea, Maui, Hawaii.
The Quaternary period represents the interval of oscillating climatic extremes (glacial and interglacial periods) beginning about 2.6 million years ago to the present. Based on modeling by the Near Earth Object (NEO) community of planetary scientists, the known and validated record of Quaternary impact on Earth by comets and asteroids is seemingly depauperate in terms of larger impactors >10,000 Mt (roughly equal to or larger than about 500 m in diameter). Modeling suggests that an average of between 2-3 and perhaps as many as 5 globally catastrophic (ca. ≥1,000,000 Mt) impacts by asteroids and comets could have occurred on Earth during this period of time, each having catastrophi c regional environmental effects and moderate to severe continental and global effects. A slightly larger number of substantive but somewhat less than globally catastrophic impacts in the 10,000-100,000 Mt range would also be predicted to have occurred during the Quaternary. However, databases of validated impact structures on Earth, contain only two examples of Quaternary period impacts in the 10,000-100,000 Mt range (Zhamanshin, Bosumtwi), dating to around a million years ago, while no examples of Quaternary period globally catastrophic impact structures have been yet identified. In addition, all of the 27 validated Quaternary period impact structures are terrestrial—no Quaternary period oceanic impacts have been yet validated. Two likely globally catastrophic probable oceanic impacts events, Eltanin (ca. 1,000,000 Mt at around 2.6 mya), and that associated with the Australasian tektite strewn field (> 1,000,000 Mt at around 0.78 mya), are known due to their debris fields for which craters have not yet been identified and validated. These and the 8-km diameter Bolivian Iturralde candidate impact structure (ca. 10,000 Mt at around 20 kya) round out our list of likely large Quaternary impact structures. This suggests that one or more Quaternary period globally catastrophic impacts and several events in the 10,000-100,000 Mt range occurred in oceanic settings and have not yet been identified. At issue here is the default position of the NEO community that no large impacts have occurred during the past 15,000 years and that there is little evidence for human death by impacts during the past 5000 years of recorded history. This bias, deriving largely from reliance on stochastic models and by selectively ignoring physical, anthropological, and archaeological evidence in support of such impacts, is apparent in the messages being given to the media and general public, and in the general lack of grant support and other assistance to scientists and scholars wishing to conduct fieldwork on impacts that may date to the past 15,000 years. Such a position has a chilling effect on what should otherwise be an important arena of inquiry into the risks and effects of cosmic impact on human society. It potentially limits advancement in our understanding of the recent record and flux of cosmic impact, and diverts attention away from significant research questions such as the possible role of impact in Quaternary period climate change and biological and cultural evolution and process.