The persistence of a chlorophyll spectral biosignature from Martian evaporite and spring analogues under Mars-like conditions
نویسندگان
چکیده
Spring and evaporite deposits are considered two of the most promising environments for past habitability on Mars and preservation of biosignatures. Manitoba, Canada hosts the East German Creek (EGC) hypersaline spring complex, and the post impact evaporite gypsum beds of the Lake St. Martin (LSM) impact. The EGC complex has microbial mats, sediments, algae and biofabrics, while endolithic communities are ubiquitous in the LSM gypsum beds. These communities are spectrally detectable based largely on the presence of a chlorophyll absorption band at 670 nm; however, the robustness of this feature underMartian surface conditions was unclear. Biological and biology-bearing samples fromEGC and LSM were exposed to conditions similar to the surface of present day Mars (high UV flux, 100mbar, anoxic, CO2 rich) for up to 44 days, and preservation of the 670 nm chlorophyll feature and chlorophyll red-edge was observed. A decrease in band depth of the 670 nm band ranging from*16 to 80% resulted, with correlations seen in the degree of preservation and the spatial proximity of samples to the spring mound and mineral shielding effects. The spectra were deconvolved to Mars Exploration Rover (MER) Pancam and Mars Science Laboratory (MSL) Mastcam science filter bandpasses to investigate the detectability of the 670 nm feature and to compare with common mineral features. The red-edge and 670 nm feature associated with chlorophyll can be distinguished from the spectra of minerals with features below *1000 nm, such as hematite and jarosite. However, distinguishing goethite from samples with the chlorophyll feature is more problematic, and quantitative interpretation using band depth data makes little distinction between iron oxyhydroxides and the 670 nm chlorophyll feature. The chlorophyll spectral feature is observable in both Pancam andMastcam, and we propose that of the proposed EXOMARS Pancam filters, the PHYLL filter is best suited for its detection. Received 1 July 2013, accepted 5 October 2013, first published online 17 December 2013
منابع مشابه
The Hydration and Dehydration of Hydrous Mixed-cation Sulfates
Introduction: Viking, Pathfinder, and the Mars Exploration Rovers and martian orbiters (e.g., Odys-sey) all support the historical and present-day existence of water on Mars. Mars Odyssey detected up to ~10 wt% equivalent H 2 O in equatorial regions of Mars where water ice is not stable [1], and a variety of hy-drated sulfate and chloride minerals have been suggested as possibly contributing to...
متن کاملAqueous Alteration in Martian Meteorites: Comparing Mineral Relations in Igneous-rock Weathering of Martian Meteorites and in the Sedimentary Cycle of Mars
Many of the minerals observed or inferred to occur in the sediments and sedimentary rocks of Mars, from a variety of Mars-mission spacecraft data, also occur in Martian meteorites. Even Martian meteorites recovered after some exposure to terrestrial weathering can preserve preterrestrial evaporite minerals and useful information about aqueous alteration on Mars, but the textures and textural co...
متن کاملTrace Element Behavior in Martian Evaporite Minerals: Experimental Constraints
Introduction: The Mars Exploration Rovers have detected distinctive suites of evaporite minerals at the Martian surface precipitated from fluids derived from basaltic weathering under low pH conditions. Orbital spectroscopic observations have confirmed the global distributions of these materials. The formation and stability of evaporite assemblages have been well modeled at Meridiani Planum for...
متن کاملExperimental studies of Mars-analog brines
Evaporite deposits may represent significant sinks of mobile cations (e.g., those of Ca, N, Mg, and Fe) and anions (e.g., those of C, N, S, and Cl) among the materials composing the Martian surface and upper crust. Carbon and nitrogen are especially interesting because of their role as atmospheric gases which can become incorporated into crustal rocks. However, the nature of evaporite precursor...
متن کاملMagnetofossils from ancient Mars: a robust biosignature in the martian meteorite ALH84001.
Magnetofossils from Ancient Mars: a Robust Biosignature in the Martian Meteorite ALH84001 Kathie L. Thomas-Keprta,* Simon J. Clemett, Dennis A. Bazylinski, Joseph L. Kirschvink, David S. McKay, Susan J. Wentworth, Hojatollah Vali, Everett K. Gibson, Jr., and Christopher S. Romanek Lockheed Martin and National Aeronautics and Space Adminstration/Johnson Space Center, Houston, Texas 77058; Depart...
متن کامل