HR: 1340h
AN: P33A-1012    [Abstracts]
TI: A Test for Past Ice Flow in the Martian North Polar Layered Deposits Based on Observed Radar Stratigraphy
AU: * Winebrenner, D P
EM: dpw@apl.washington.edu
AF: Applied Physics Laboratory, Box 355640 University of Washington, Seattle, WA 98195, United States
AU: * Winebrenner, D P
EM: dpw@apl.washington.edu
AF: Dept. of Earth and Space Sciences, Box 351310 University of Washington, Seattle, WA 98195, United States
AU: Holt, J W
EM: jack@utig.ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics University of Texas - Austin, Austin, TX 78758, United States
AU: Safaeinili, A
EM: ali.safaeinili@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Koutnik, M R
EM: mkoutnik@u.washington.edu
AF: Dept. of Earth and Space Sciences, Box 351310 University of Washington, Seattle, WA 98195, United States
AU: Waddington, E D
EM: edw@ess.washington.edu
AF: Dept. of Earth and Space Sciences, Box 351310 University of Washington, Seattle, WA 98195, United States
AU: Pathare, A V
EM: avp11235@gmail.com
AF: Planetary Science Institute, 1700 East Fort Lowell Suite 106, Tucson, AZ 85719, United States
AU: Byrne, S
EM: sbyrne@u.arizona.edu
AF: Dept. of Planetary Sciences, University of Arizona, Tucson, AZ 85721,
AU: Murray, B M
EM: bcm@caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology MC 170-25, Pasadena, CA 91125, United States
AB: Recent analysis of surface topography on the North Polar Layered Deposits (NPLD), specifically Gemina Lingula, has yielded evidence for a period of near-balance between ice flow and surface mass fluxes, followed by a period of trough formation. In this scenario, ice flow during the period of balance acted to equilibrate accumulation (positive surface mass balance) at higher elevations with ablation (negative surface mass balance) at lower elevations. Locations where the surface mass balance changed sign are predicted by fitting an ice-flow model to present-day, inter-trough topography (Winebrenner et al., submitted). Assuming that internal layers are isochrones, this mass-balance pattern implies that layers will intersect the surface only in the ablation zone. Here we test this prediction using observations of radar stratigraphy within Gemina Lingula made with the Shallow Subsurface Radar (SHARAD) aboard the Mars Reconnaissance Orbiter (MRO). More than 100 profiles of radar data over Gemina Lingula have thus far been acquired, along ground tracks determined by orbital parameters rather than possible ice dynamics in the area. We therefore trace layers on many tracks and fit surfaces to layer locations, so as to infer layering along the prospective paths of past flow. We focus initially on the area of Gemina Lingula between its central ridge and Chasma Boreale, where radar observation of internal layering is simpler because high-elevation troughs are rare, and trough geometries at lower elevations are simple relative to those on the equatorward side of the ridge. Our ice-flow model accurately fits high-elevation topography, but places the ice margin during the period of balance well inside what now is Chasma Boreale. We thus far observe no radar layers near the ridge that intersect the ice surface, consistent with our inference of accumulation in that region during the period of balance.
DE: 0726 Ice sheets
DE: 3260 Inverse theory
DE: 5416 Glaciation
DE: 5462 Polar regions
DE: 5464 Remote sensing
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting