loading page

Replenishment of near-surface water ice by impacts into Ceres’ volatile-rich crust: Observations by Dawn’s Gamma Ray and Neutron Detector
  • +11
  • Thomas H. Prettyman,
  • Naoyuki Yamashita,
  • Margaret E Landis,
  • Julie C Castillo-Rogez,
  • Norbert Schorghofer,
  • Carle M. Pieters,
  • Hanna G. Sizemore,
  • Harald Hiesinger,
  • Simone Marchi,
  • Harry Y McSween,
  • Ryan S. Park,
  • Michael J Toplis,
  • Carol A. Raymond,
  • C. T. Russell
Thomas H. Prettyman
Planetary Science Institute

Corresponding Author:[email protected]

Author Profile
Naoyuki Yamashita
Planetary Science Institute
Author Profile
Margaret E Landis
University of Colorado, Boulder
Author Profile
Julie C Castillo-Rogez
Jet Propulsion Laboratory
Author Profile
Norbert Schorghofer
Planetary Science Institute
Author Profile
Carle M. Pieters
Brown University
Author Profile
Hanna G. Sizemore
Planetary Science Institute
Author Profile
Harald Hiesinger
Westfälische Wilhelms-Universität Münster
Author Profile
Simone Marchi
Southwest Research Institute
Author Profile
Harry Y McSween
University of Tennessee at Knoxville
Author Profile
Ryan S. Park
Jet Propulsion Laboratory
Author Profile
Michael J Toplis
Institut de Recherche en Astrophysique et Planetologie
Author Profile
Carol A. Raymond
JPL
Author Profile
C. T. Russell
University of California, Los Angeles
Author Profile

Abstract

Ceres’ regolith contains water ice that has receded in response to insolation-driven sublimation. Specially targeted, high spatial-resolution measurements of hydrogen by Dawn’s Gamma Ray and Neutron Detector reveal elevated hydrogen concentrations in and around Occator, a young, 90-km diameter, complex crater located at 19.82N where near-surface ice is not expected. The excess hydrogen is explained by impact excavation of water-rich outer crustal materials and their emplacement in the crater floor and ejecta blanket. This is supported by thermophysical models that show water ice could survive at sub-meter depths, given Occator’s relatively young age (~20 Myr). We hypothesize that the regolith can be replenished with ice from large impacts and that this process partially controls the distribution and depth of near surface ice. This is supported by results from Occator and similarities in the global distribution of hydrogen and the pattern of large craters (20-100 km diameter).