HR: 0830h
AN: C21C-0826    [PDF]
TI: Potential Ground Ice and Small-Scale Polygons on Mars
AU: Klima, R
EM: Rachel_Klima@brown.edu.
AF: Univ. of Illinois at Chicago, Dept. of Earth & Environmental Sciecnes 845 W. Taylor St., Chicago, IL 60607 United States
AU: * Forman, S L
EM: slf@uic.edu
AF: Univ. of Illinois at Chicago, Dept. of Earth & Environmental Sciecnes 845 W. Taylor St., Chicago, IL 60607 United States
AU: Doran, P
EM: Pdoran@uic.edu
AF: Univ. of Illinois at Chicago, Dept. of Earth & Environmental Sciecnes 845 W. Taylor St., Chicago, IL 60607 United States
AU: Kargel, J S
EM: jkargel@usgs.gov
AF: U.S. Geological Survery, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AB: Martian geomorphology reveals many Martian landforms suggesting the presence of ground ice-rich sediment. Fractured polygonal networks, which are similar in size and shape to polygons commonly found in Earth's permafrost and desiccated lake and stream beds, are observed in numerous localities at middle and high latitudes on Mars, but are rare at low latitudes. If polygons on Mars form similarly to those on Earth, they would provide information about the distribution and history of the Martian hydrosphere and especially the cryosphere. Although these and other features have been compared morphologically to those on Earth, there has previously been no way to independently determine whether the process which formed the polygons on Mars also involves ground ice or water. The Mars Odyssey mission, specifically the Gamma Ray Spectrometer (GRS), has provided unprecedented maps of subsurface hydrogen on Mars. Presented is the global polygon distribution in context with recent measurements of near-surface hydrogen abundance. Of roughly 34,000 narrow angle MOC images investigated, 730 sites containing polygons were identified. A cluster in Utopia Planitia (centered at ~45$\deg$N, 90$\deg$E) accounts for about 15% of total sites. Excluding the polygons in Utopia Planitia, 99% of sites correspond with hydrogen levels measured by epithermal neutron flux that are equivalent to or $>$35% water ice by weight. MOC images from Utopia Planitia show the presence of beaded-drainage within polygonal permafrost-like features, and gravity- driven slumps indicating flowing liquids in Amazonian time.
DE: 5462 Polar regions
DE: 5470 Surface materials and properties
DE: 5499 General or miscellaneous
DE: 6255 Neptune
SC: Cryosphere [C]
MN: 2003 Fall Meeting