Geology of the Selk crater region on Titan from Cassini VIMS observations

Research areas:
  • Jason M. Soderblom
  • Robert H. Brown
  • Laurence A. Soderblom
  • Jason W. Barnes
  • Ralf Jaumann
  • Stéphane Le Mouélic
  • Christophe Sotin
  • Katrin Stephan
  • Kevin H. Baines
  • Bonnie J. Buratti
  • Roger N. Clark
  • Philip D. Nicholson
Observations of Titan obtained by the Cassini Visual and Infrared
Mapping Spectrometer (VIMS) have revealed Selk crater, a geologically
young, bright-rimmed, impact crater located similar to 800 km
north-northwest of the Huygens landing site. The crater rim-crest
diameter is 90 km; its floor diameter is similar to 60 km. A central
pit/peak, 20-30 km in diameter, is seen; the ratio of the size of this
feature to the crater diameter is consistent with similarly sized
craters on Ganymede and Callisto, all of which are dome craters. The
VIMS data, unfortunately, are not of sufficient resolution to detect
such a dome. The inner rim of Selk crater is fluted, probably by eolian
erosion, while the outer flank and presumed ejecta blanket appear
dissected by drainages (particularly to the east), likely the result of
fluvial erosion. Terracing is observed on the northern and western walls
of Selk crater within a 10-15 km wide terrace zone identified in VIMS
data; the terrace zone is bright in SAR data, consistent with it being a
rough surface. The terrace zone is slightly wider than those observed on
Ganymede and Callisto and may reflect differences in thermal structure
and/or composition of the lithosphere. The polygonal appearance of the
crater likely results from two preexisting planes of weakness (oriented
at azimuths of 21 degrees and 122 degrees east of north). A unit of
generally bright terrain that exhibits similar infrared-color variation
and contrast to Selk crater extends east-southeast from the crater
several hundred kilometers. We informally refer to this terrain as the
Selk ``bench.{''} Both Selk and the bench are surrounded by the
infrared-dark Belet dune field. Hypotheses for the genesis of the
optically bright terrain of the bench include: wind shadowing in the lee
of Selk crater preventing the encroachment of dunes, impact-induced
cryovolcanism, flow of a fluidized-ejecta blanket (similar to the bright
crater outflows observed on Venus), and erosion of a streamlined upland
formed in the lee of Selk crater by fluid flow. Vestigial circular
outlines in this feature just east of Selk's ejecta blanket suggest that
this might be a remnant of an ancient, cratered crust. Evidently the
southern margin of the feature has sufficient relief to prevent the
encroachment of dunes from the Belet dune field. We conclude that this
feature either represents a relatively high-viscosity, fluidizedejecta
flow (a class intermediate to ejecta blankets and long venusian-style
ejecta flows) or a streamlined upland remnant that formed downstream
from the crater by erosive fluid flow from the west-northwest. (C) 2010
Elsevier Inc. All rights reserved.