HR: 0800h
AN: P41A-08    [Abstracts]
TI: Zinc on Mars
AU: * Yen, A
EM: Albert.Yen@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, MS 183-501, Pasadena, CA 91109, United States
AU: Clark, B
EM: Benton.C.Clark@lmco.com
AF: Lockheed Martin Corporation, MS S8000, Littleton, CO 80127, United States
AU: Gellert, R
EM: ralf@physics.uoguelph.ca
AF: University of Guelph, Department of Physics, Guelph, ON N1G 2W1, Canada
AU: Morris, R
EM: Richard.V.Morris@nasa.gov
AF: NASA Johnson Space Center, Code KR, Houston, TX 77058, United States
AU: Science Team, A
EM: squyres@astrosun.tn.cornell.edu
AF: Cornell University, Department of Astronomy, Ithaca, NY 14853, United States
AB: Unambiguous detections of zinc on Mars, with certain measurements in excess of 1500 ppm, have been established by the Alpha Particle X-ray Spectrometers onboard the Mars Exploration Rovers. Several distinct trends in the behavior of zinc are evident in this data set: (1) Zn is clearly correlated with sulfur, chlorine, and, as measured by the Moessbauer spectrometers, a nanophase ferric oxide in over 50 analyses of martian soils at landing sites separated by 180 degrees of longitude. This relationship suggests that Zn, S, and Cl may be volcanic emissions condensed on soil grains and/or that these components (including the nanophase iron oxide) are associated with minor amounts of weathering in these ferrous iron dominated samples. No distinct sulfate, chloride, or zinc mineral phase is present in these soils. (2) A certain class of rocks (Wishstone/Watchtower) at the Gusev Crater landing site, characterized by elevated P and Ti with Cr at or near the detection limit, shows higher levels of Zn for samples with a higher ratio of ferric to total iron. In this case, Zn is an indicator of alteration in these nearly isochemical samples. (3) In the Wishstone/Watchtower samples and in other altered rocks (Clovis class), Zn is correlated with Cl. In terrestrial Cl-rich fluids, the Zn:Cl ratio is an indicator of the temperature of the fluids which interacted with the deposits. The slope of the Zn-Cl line in these rocks is shallower than the fit through the soil data, consistent with a lower temperature origin of this zinc signature. Finally, (4) the highest levels of Zn detected on Mars thus far approach 2300 ppm and are correlated with Cl. In this sample, hematite dominates the iron mineralogy, and thermal alteration is suggested.
DE: 1027 Composition of the planets
DE: 5220 Hydrothermal systems and weathering on other planets
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Joint Assembly