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Snow Crash: Compaction Craters on (486958) Arrokoth and Other Small KBOs
  • +13
  • William B. McKinnon,
  • Xiaochen Mao,
  • Paul Schenk,
  • Kelsi Nab Singer,
  • Stuart James Robbins,
  • Oliver Luke White,
  • Ross Beyer,
  • Simon B. Porter,
  • James Tuttle Keane,
  • Daniel BRITT,
  • John R. Spencer,
  • William M. Grundy,
  • Jeffrey M. Moore,
  • S. Stern,
  • Harold Weaver,
  • Catherine Olkin
William B. McKinnon
Washington University in St. Louis

Corresponding Author:[email protected]

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Xiaochen Mao
Washington University in St. Louis
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Paul Schenk
LPI
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Kelsi Nab Singer
Southwest Research Institute
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Stuart James Robbins
Southwest Research Institute
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Oliver Luke White
NASA Ames Research Center
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Ross Beyer
SETI
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Simon B. Porter
Southwest Research Institute
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James Tuttle Keane
NASA Jet Propulsion Laboratory, California Institute of Technology
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Daniel BRITT
University of Central Florida, Department of Physics
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John R. Spencer
Southwest Research Institute
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William M. Grundy
Lowell Observatory
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Jeffrey M. Moore
NASA Ames Research Center
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S. Stern
Southwest Research Institute
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Harold Weaver
Johns Hopkins University
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Catherine Olkin
Unknown
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Abstract

Evidence from Arrokoth and comets strongly suggests a very low density for this and similar small Kuiper belt objects. Plausible compositions imply very high porosities, in excess of 70%, and low compaction crush strengths. If so, craters on Arrokoth (especially Sky, its largest) formed largely by compaction of pore space and material displacement. This is consistent with geological evidence from New Horizons imaging. High porosity reduces cratering efficiency in the gravity regime whereas compaction moves it towards a crush strength scaling. Compaction also guarantees that most impactor kinetic energy is taken up as waste heat near the impact point, with momentum transferred to the rest of the body by elastic waves only. Monte Carlo simulations of Sky-forming conditions indicate that the momentum imparted likely separated Arrokoth’s two lobes, but displacement was limited by dissipation at the neck. Unusual strength properties are not required to preserve Arrokoth’s bilobate configuration.