HR: 1340h
AN: P43A-0910    [Abstracts]
TI: Maximum Age Predictions for Optical Dating on Mars Based on Dose/Depth Models and Martian Meteorite Compositions
AU: * Franklund, R T
EM: Roark.Franklund@ndsu.nodak.edu
AF: North Dakota State University, Department of Geosciences 218 Stevens Hall, Fargo, ND 58105 United States
AU: Lepper, K
EM: ken.lepper@ndsu.nodak.edu
AF: North Dakota State University, Department of Geosciences 218 Stevens Hall, Fargo, ND 58105 United States
AB: A fundamental need in the Mars exploration portfolio is in-situ absolute dating. Optical dating has been proposed for determining the age of Mars surface features and landforms as well as the rates of martian surface processes. On Earth, the method is employed for Quaternary studies because the technique currently has a terrestrial maximum age limit of approximately 350 ka. This maximum age limit is a function of the saturation dose of the dosimeter material (silicate sediments) and the local ionizing radiation dose rate. The sources of ionizing radiation germane to optical dating are K, Rb, U, Th in the sediment/soil environment and cosmic rays. On Mars the near surface dose rate will be dominated by cosmic rays, however, at depth the decay of radioisotopes will be the principle contributor of ionizing radiation. In this work we present an evaluation of the maximum age limits for OSL dating on Mars as a function of depth. At this time we have considered only static burial. Our calculations are based on published models of and data for: (i) Mars surface cosmic dose rate and its attenuation by martian regolith, (ii) elemental analyses of Mars meteorites, (iii) an experimental evaluation of the saturation dose for the martian soil simulant JSC Mars-1. Our analysis confirms earlier inferences that optical dating should have a greater effective age range on Mars than on Earth. At depths easily accessible by penetrators or moles (1-3 m), maximum optical ages greater than 600 ka are possible. Geochronology on this scale would include at least two stadial/interstadial cycles within Mars' last "Glacial Epoch" (synchronized insolation variations between the poles). A wide range of landforms and surface processes associated with climate variability -- e.g. outwash and lacustrine deposition, large-scale eolian activation -- could potentially be optically dated. At greater depths, that could be reached by mobile drilling rigs or cryobots (10-30m), optical age maximums of 4.5 to greater than 35 Ma appear to be possible.
UR: http://www.ndsu.nodak.edu/ndsu/klepper/ODDSQUAD/
DE: 5416 Glaciation
DE: 5460 Physical properties of materials
DE: 5462 Polar regions
DE: 5470 Surface materials and properties
DE: 5494 Instruments and techniques
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting