Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p12a..02w&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P12A-02
Physics
[5419] Planetary Sciences: Solid Surface Planets / Hydrology And Fluvial Processes
Scientific paper
Qinghai-Tibet (QT) Plateau has the highest average elevation on Earth (~ 4500 m, about 50-60% of atmospheric pressure at sea-level). The high elevation induces a tremendous diurnal (and seasonal) temperature swing caused by high level of solar irradiation during the day and low level of atmospheric insulation during the evening. In addition, the Himalaya mountain chain (average height >6100 m) in the south of the QT Plateau largely blocks the pathway of humid air from the Indian Ocean, and produces a Hyperarid region (Aridity Index, AI ~ 0.04), the Qaidam Basin (N32-35, E90-100) at the north edge of the QT Plateau. Climatically, the low P, T, large ΔT, high aridity, and high UV radiation all make the Qaidam basin to be one of the most similar places on Earth to Mars. Qaidam basin has the most ancient playas (up to Eocene) and the lakes with the highest salinity on QT Plateau. More importantly, Mg-sulfates appear in the evaporative salts within the most ancient playas (Da Langtang) at the northwest corner of Qaidam basin, which mark the final stage of the evaporation sequence of brines rich in K, Na, Ca, Mg, Fe, C, B, S, and Cl. The evaporation minerals in the saline playas of Qaidam basin, their alteration and preservation under hyperarid conditions can be an interesting analog for the study of Martian salts and salty regolith. We conducted a field investigation at Da Langtan playa in Qaidam basin, with combined remote sensing (ASTER on board of NASA’s Terra satellite, 1.656, 2.167, 2.209, 2.62, 2.336, 2.40 µm), in situ sensing of a portable NIR spectrometer (WIR, 1.25-2.5 µm continuous spectral range), and the laboratory analyses of collected samples from the field (ASD spectrometer, 0.4 -2.5 µm, and Laser Raman spectroscopy). The results indicate that the materials contributing the high albedo layers in playa deposits are carbonate-gypsum-bearing surface soils, salt-clay-bearing exhaumed Pleistocene deposits, dehydrated Na-sulfates, hydrous Mg- & multication-sulfates, carbonates, and chlorites. Halophiles were isolated from the collected evaporative salt samples from Da Langtan. They were cultured on modified growth medium (MGM) under different salinity conditions, and eight strains of halobacteria showed different growth curves. 16S rRNA gene sequences for these eight strains suggested that the halophiles from Da Langtan had high homology with some species of genera of Virgibacillus, Oceanobacillus, Halobacillus, and Ter-ribacillus. In conclusion, the climatic conditions and salt mineralogy within the lacustrine deposits at Da Langtan playa, northwest corner of the Qaidam basin on Qinghai-Tibet Plateau, indicate that this area can be an excellent analog site for studying the precipitation sequence and the subsequent dehydration/degeneration of Martian salts. The finding of hylophyles in this hyperarid environment boosts the importance of exploring salty regolith in future surface explorations to Mars (MSL and ExoMars) in the search for similar biosignatures.
Kong Fan
Mayer D. P.
Sobron Pablo
Wang Anzhong
Zheng Manli
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