IDENTIFYING SUITABLE TERRESTRIAL ANALOGS OF MARS SHOREZONE FEATURES: PLANETARY EXPLORATION GUIDELINES
JEWELL, Paul, Dept. of Geology and Geophysics, Univ. of Utah, Salt Lake City, UT 84112, CHAN, Marjorie, Dept. of Geology and Geophysics, Univ. of Utah, Geology & Geophysics Frederick Albert Sutton Building, 115 S 1460 E, Room 383, Salt Lake City, UT 84112, NICOLL, Kathleen, University of Utah, 260 South Central Campus Dr, Salt Lake City, UT 84105, PARKER, Timothy, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, OKUBO, Chris H., Astrogeology Science Center, US Geological Survey, 2255 North Gemini Road, Flagstaff, AZ 86001, KOMATSU, Goro, Irsps, Univ. G.d'Annunzio, Viale Pindaro, 42, 65127, Pescara, Italy, ORMO, Jens, Centro de Astrobiologia, Torrejon de Ardoz, 28850, Spain and BARKER, Donald, Earth and Atmospheric Sciences, University of Houston, 312 Science & Research Building 1, Rm. 312, Houston, TX 77204, paul.jewell@utah.edu
The nature or even the past existence of a large water body on Mars has been the subject of intense controversy and is a driving force behind selection of future exploration sites on the Red Planet. Whatever the nature of Martian oceans or lakes, they were almost certainly subjected to physical forcings and climate with no direct analog in Earth’s geologic history. Nevertheless, any large body of water that remains in the same place for an extended period of time invariably leaves a physical record of its presence at the water-atmosphere interface. In the case of oceans and large lake shorezones on Earth this record includes shorelines, strandlines, beach ridges, and other physical manifestations. Recognition of these features depends on their geomorphic expression (length, relation to surrounding topography) and sedimentary character (textures, structures, or chemical deposits such as tufa).
For many years to come, recognition of possible shorezone features on Mars must rely on remote sensing instruments that in turn will be a function of the spatial resolution and spectral capabilities of these instruments and relating the resulting images to Earth analogs. Unfortunately, a large percentage of appropriate shorezone Earth analogs are (1) too subtle or small to be detected by currently deployed Martian instrumentation or (2) distinguished by vegetation patterns which in turn are a function of the sedimentary characteristics of the substrate and thus are not appropriate analogs for the modern surface of Mars. Appropriate Earth analogs for Martian shorelines must necessarily be restricted to a narrow suite of shoreline features. Specific examples from ice age water bodies Lake Bonneville, Lake Agassiz, Baltic Ice Lake and the modern Great Lakes provide guidelines for recognizing shorezone features on Mars and should guide the search for paleo-oceans and paleo-lakes on the Red Planet.
