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Title: Constraints on planetesimal disk mass from the cratering record and equatorial ridge on Iapetus

Iapetus, the outermost regular satellite of Saturn, has a drastic albedo dichotomy and an equatorial circumferential ridge that reaches heights of 20 km and widths of 70 km. This moon is thought to have formed concurrently with Saturn, and so would have experienced an intense bombardment after its formation. The ridge, which has been inferred to be one of the most ancient features on Iapetus' surface, could reasonably be expected to have been eroded by impacts; however, it has retained long continuous sections and a nearly pristine triangular shape with ridge slopes reaching ∼40°. We use these observations, along with crater counts on Iapetus' surface, to constrain the total bombardment mass experienced by the satellite since its formation. The ridge morphology and the global crater population recorded on Iapetus both suggest similar bombardment masses, indicating the ridge is indeed ancient. We find that the inferred total bombardment mass incident on Iapetus is less than 20% of the bombardment predicted by the classic Nice model for early solar system evolution. Our results, though, support the recently proposed scenarios of planetesimal-driven migration of the young outer planets including more realistic disk conditions.
Authors:
; ;  [1] ;  [2] ;  [3]
  1. Department of Earth, Environmental, and Planetary Sciences, Brown University, 324 Brook Street, Box 1846, Providence, RI 02912 (United States)
  2. Southwest Research Institute, 1050 Walnut Street, Suite 200, Boulder, CO 80302 (United States)
  3. Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058 (United States)
Publication Date:
OSTI Identifier:
22365088
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 792; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ALBEDO; CRATERS; MASS; MIGRATION; MOON; SATURN PLANET; SOLAR SYSTEM EVOLUTION; SURFACES