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marchant

HR: 13:55h
AN: P32B-02
TI: Geological Evidence for Recent Ice Ages on Mars
AU: * Head, J W
EM: James_Head_III@brown.edu
AF: Dept. of Geological Sciences Brown University, Box 1846, Providence, RI 02912 United States
AU: Mustard, J F
EM: John_Mustard@brown.edu
AF: Dept. of Geological Sciences Brown University, Box 1846, Providence, RI 02912 United States
AU: Kreslavsky, M A
EM: misha@mare.geo.brown.edu
AF: Dept. of Geological Sciences Brown University, Box 1846, Providence, RI 02912 United States
AU: Kreslavsky, M A
EM: misha@mare.geo.brown.edu
AF: Astronomical Institute, Kharkov National University, Kharkov, 310022 Ukraine
AU: Milliken, R E
Milliken@brown.edu
AF: Dept. of Geological Sciences Brown University, Box 1846, EM: Ralph_ Providence, RI 02912 United States
AU: Marchant, D R
EM: marchant@bu.edu
AF: Dept. of Earth Sciences Boston University, 685 Commonwealth Avenue, Boston, MA 02215
AB: A primary cause of ice ages on Earth is orbital forcing from variations in orbital parameters of the planet. On Mars such variations are known to be much more extreme. Recent exploration of Mars has revealed abundant water ice in the near-surface at high latitudes in both hemispheres. We outline evidence that these near-surface, water-ice rich mantling deposits represent a mixture of ice and dust that is layered, meters thick, and latitude dependent. These units were formed during a geologically recent major martian ice age, and were emplaced in response to the changing stability of water ice and dust on the surface during variations in orbital parameters. Evidence for these units include a smoothing of topography at subkilometer baselines from about 30$^{o}$ north and south latitudes to the poles, a distinctive dissected texture in MOC images in the +/-30$^{o}$-60$^{o}$ latitude band, latitude-dependent sets of topographic characteristics and morphologic features (e.g., polygons, 'basketball' terrain texture, gullies, viscous flow features), and hydrogen concentrations consistent with the presence of abundant ice at shallow depths above 60$^{o}$ latitude. The most equatorward extent of these ice-rich deposits was emplaced down to latitudes equivalent to Saudi Arabia and the southern United States on Earth during the last major martian ice age, probably about 0.4-2.1 million years ago. Mars is currently in an inter-ice age period and the ice-rich deposits are presently undergoing reworking, degradation and retreat in response to the current stability relations of near-surface ice. Unlike Earth, martian ice ages are characterized by warmer climates in the polar regions and the enhanced role of atmospheric water ice and dust transport and deposition to produce widespread and relatively evenly distributed smooth deposits at mid-latitudes during obliquity maxima.
DE: 5416 Glaciation
DE: 5455 Origin and evolution
DE: 5470 Surface materials and properties
DE: 6207 Comparative planetology
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting