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AGU: Journal of Geophysical Research, Planets

 

Keywords

  • MESSENGER
  • Mercury
  • craters
  • north pole
  • shadow
  • water ice

Index Terms

  • 5462 - Polar regions
  • 6235 - Mercury

Paper in Press

JOURNAL OF GEOPHYSICAL RESEARCH, doi:10.1029/2012JE004172

Craters hosting radar-bright deposits in Mercury's north polar region: Areas of persistent shadow determined from MESSENGER images

Key Points
  • MESSENGER images provide a nearly complete view of Mercury's north polar region
  • Radar-bright deposits at Mercury's north pole map to areas of persistent shadow
  • Radar-bright features in shadowed areas are consistent with water ice on Mercury

Authors:

Nancy Lynne Chabot

Carolyn Ernst

John Knud Harmon

Scott L. Murchie

Sean C. Solomon

David T. Blewett

Brett W Denevi

Radar-bright features near Mercury's poles were discovered in Earth-based radar images and proposed to be water ice present in permanently shadowed areas. Images from MESSENGER's one-year primary orbital mission provide the first nearly complete view of Mercury's north polar region, as well as multiple images of the surface under a range of illumination conditions. We find that radar-bright features near Mercury's north pole are associated with locations persistently shadowed in MESSENGER images. Within 10{degree sign} of the pole, almost all craters larger than 10 km in diameter host radar-bright deposits. There are several craters located near Mercury's north pole with sufficiently large diameters to enable long-lived water ice to be thermally stable at the surface within regions of permanent shadow. Craters located farther south also host radar-bright deposits and show a preference for cold-pole longitudes; thermal models suggest that a thin insulating layer is required to cover these deposits if the radar-bright material consists predominantly of long-lived water ice. Many small (<10 km diameter) and low-latitude (extending southward to 66{degree sign}N) craters host radar-bright material, and water ice may not be thermally stable in these craters for ~ 1 Gy, even beneath an insulating layer. The correlation of radar-bright features with persistently shadowed areas is consistent with the deposits being composed of water ice, and future thermal modeling of small and low-latitude craters has the potential to further constrain the nature, source, and timing of emplacement of the radar-bright material.

Received 27 June 2012; accepted 1 November 2012.

Citation: Chabot, N. L., C. Ernst, J. K. Harmon, S. L. Murchie, S. C. Solomon, D. T. Blewett, and B. W. Denevi (2012), Craters hosting radar-bright deposits in Mercury's north polar region: Areas of persistent shadow determined from MESSENGER images, J. Geophys. Res., doi:10.1029/2012JE004172, in press.