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History of the Terminal Cataclysm Paradigm: Epistemology of a Planetary Bombardment That Never (?) Happened

Planetary Science Institute, 1700 East Fort Lowell Road, Suite 106, Tucson, AZ 85719, USA
Geosciences 2019, 9(7), 285; https://doi.org/10.3390/geosciences9070285
Received: 30 November 2018 / Revised: 28 May 2019 / Accepted: 30 May 2019 / Published: 28 June 2019
(This article belongs to the Special Issue Recent Advances in Lunar Studies)
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Abstract

This study examines the history of the paradigm concerning a lunar (or solar-system-wide) terminal cataclysm (also called “Late Heavy Bombardment” or LHB), a putative, brief spike in impacts at ~3.9 Ga ago, preceded by low impact rates. We examine origin of the ideas, why they were accepted, and why the ideas are currently being seriously revised, if not abandoned. The paper is divided into the following sections: Overview of paradigm. Pre-Apollo views (1949–1969). Initial suggestions of cataclysm (ca. 1974). Ironies. Alternative suggestions, megaregolith evolution (1970s). Impact melt rocks “establish” cataclysm (1990). Imbrium redux (ca. 1998). Impact melt clasts (early 2000s). Dating of front-side lunar basins? Dynamical models “explain” the cataclysm (c. 2000s). Asteroids as a test case. Impact melts predating 4.0 Ga ago (ca. 2008–present.). Biological issues. Growing doubts (ca. 1994–2014). Evolving Dynamical Models (ca. 2001–present). Connections to lunar origin. Dismantling the paradigm (2015–2018). “Megaregolith Evolution Model” for explaining the data. Conclusions and new directions for future work. View Full-Text
Keywords: terminal cataclysm; late heavy bombardment; LHB; lunar impact basin formation; regolith; megaregolith; paradigms in planetary science; cratering; lunar impact basin ages; lunar origin terminal cataclysm; late heavy bombardment; LHB; lunar impact basin formation; regolith; megaregolith; paradigms in planetary science; cratering; lunar impact basin ages; lunar origin
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Hartmann, W.K. History of the Terminal Cataclysm Paradigm: Epistemology of a Planetary Bombardment That Never (?) Happened. Geosciences 2019, 9, 285.

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