HR: 1340h
AN: P13A-0982    [Abstracts]
TI: Young (late Amazonian), near surface, ground ice features near the equator, Athabasca Valles, Mars
AU: * Burr, D M
EM: dmburr@usgs.gov
AF: USGS Astrogeology Program, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AU: Soare, R J
EM: rsoare@colba.net
AF: Dept. of Geography Concordia University, 1455 de Maisonneuve West, Montreal, H3G 1M8 Canada
AU: Soare, R J
EM: rsoare@colba.net
AF: Dept. of Geography Burnside Hall McGill University, 805 Sherbrooke St. West, Montreal, H3A 2K6 Canada
AU: Wan Bun Tseung, J
EM: bonbonmou2@videotron.ca
AF: Dept. of Geography Concordia University, 1455 de Maisonneuve West, Montreal, H3G 1M8 Canada
AB: A suite of four feature types near 10N 204W in Athabasca Valles are interpreted to have resulted from near-surface ground ice. These features include mounds, conical forms with rimmed summit depressions, flatter irregularly-shaped forms with raised rims, and polygonal terrain. Based on morphology, size, and analogy to terrestrial ground ice forms, these Athabascan features are interpreted as pingos, collapsing pingos, pingo scars, and thermal contraction polygons, respectively. THEMIS night IR data and surficial geological features in the area indicate that a sedimentary substrate comprises these features. In conjunction with morphology, this supports a ground ice interpretation over alternative (volcanic) hypotheses. The ground ice that formed the mounds and rimmed features may have derived from the deposition of saturated sediment during flooding; alternatively, the ground ice may have derived from magmatically cycled groundwater. The ground ice implicit in the hypothesized thermal contraction polygons may have derived either from flooding or from atmospheric water. The lack of flood modification of the mounds and rimmed features indicates that their formation took place more recently than the last flood inundated the area. Analogy with terrestrial pingos suggests that ground ice is still extant within the positive relief mounds beneath less than a few meters of overburden. As the water that flooded down Athabasca Valles emerged via a volcanotectonic fissure from a deep aquifer, this pingo ice may contain evidence of a deep subsurface biosphere.
DE: 5499 General or miscellaneous
DE: 6225 Mars
DE: 1823 Frozen ground
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting