NASA Astrobiology Institute (NAI)

1. Iron, the Oxygen Transition, UV Shielding, and Photosynthesis

   Project Investigators: Janice Bishop

   Other Project Members

   Mario Parente (Doctoral Student)

   Melissa Lane (Collaborator)

   Darby Dyar (Collaborator)

   Summary

   Our combined field and lab work has shown that iron oxide bearing minerals could be important in protecting photosynthetic organisms from UV radiation and that nanophase ferric oxyhydroxides in a clay matrix are particularly effective. We have collected several iron-rich samples from hot springs where microbes thrive and are completing characterizing the minerals present and their spectral properties. We are also identifying iron oxides and clay minerals on Mars in order to determine possible environments where microbes could have been protected from solar radiation.

   Astrobiology Roadmap Objectives:

   • Objective 2.1: Mars exploration

   Project Progress

   Janice Bishop & Lynn Rothschild- We continued analysis of the spectral properties of Fe-bearing Mars analog sites on Earth and analyzing spectra of Mars for Fe oxide-bearing components. We are preparing the data on samples from Yellowstone National Park (YNP) and Bolivia for publication. Spectra of materials from the YNP Chocolate Pots site (Figure 1) show the presence of nanophase iron oxides/oxyhydroxides that may be facilitating growth of photosynthetic organisms in these natural environments by providing protection from UV radiation. An image of the YNP Chocolate Pots site is shown in Figure 2. Based on the spectral properties of iron oxides and the results of experiments with two photosynthetic organisms, we propose a scenario where photosynthesis, and ultimately the oxygenation of the atmosphere, depended on the protection of early microbes by nanophase ferric oxides/oxyhydroxides. Such niches may have also existed on Mars.

   Work this year on the bright salty soils found at Paso Robles and other sites in Gusev crater showed that this material is composed of the ferric minerals ferricopiapite, fibroferrite and/or ferristrunzite (Lane et al., 2008, Parente et al., 2008). Pancam multispectral visible/near-infrared (VNIR) images of Mars from Gusev crater are shown in Figures 2 and 3. Analysis of these Pancam data together with the mini-TES and MÖssbauer data collected by MER enabled characterization of the minerals in the bright salty soils. Although these sulfates may imply the presence of brines too salty for many microbes, the UV-VIS properties of these ferric minerals could have provided solar protection for microbes able to withstand the salty conditions.

   Analysis of MRO/CRISM hyperspectral VNIR images of Mars showed the presence of a large phyllosilicate outcrop at Mawrth Vallis, one of the potential landing sites for future missions. The most abundant clay phase found here is an Fe/Mg-smectite. The depth and breadth of this clay deposit suggests long-standing water on Mars (Bishop et al., 2008). The iron-bearing clay also absorbs some of the UV-VIS solar radiation and could have provided solar protection to microbes if present. A border of Fe²⁺ material in between the Fe³⁺ and Al clays suggests a change in chemistry typically associated with microbial activity on Earth. This shows an active early chemistry in these ancient martian rocks.

   
   

   Figure 1 Reflectance spectra of two chocolate pots samples show that these are dominated by ferrihydrite: A) VNIR region and B) mid-IR region. Chocolate Pots-1 (orange) exhibits spectral features consistent with pure ferrihydrite, while the spectrum of Chocolate Pots-2 (red) contains less clear ferrihydrite bands and additional features due to other phases. These are compared with spectra of natural ferrihydrite-bearing precipitates from Iceland. The dark green spectrum exhibits the features due to pure ferrihydrite, while the light green spectrum indicates the presence of some impurity phases.

   
   

   Figure 2 Approximate true color Pancam Image of bright yellow and white soils exposed by rover wheel tracks at Paso Robles in Gusev crater, Mars.

   
   

   Figure 3 Pancam images of bright salty material at Paso Robles in Gusev crater, Mars. a & d) show R=673 G=535 B=436 nm (dust as dark red and sulfate-rich phases as white and yellow). c) shows R=482 G=753 B=864 nm (shows sulfate unit similar at these channels). b,e & f) map end-member components with R=dust, G=bright white, yellow and pink material from a & f), B=shade.

   
   

   Figure 4 Map of clays in Mawrth Vallis, Mars, made from CRISM image draped over MOLA terrain. Fe/Mg-phyllosilicate is shown in red, Al-phyllosilicate is shown in blue, hydrated silica and an Fe2+ phase is shown in yellow/green.

   Mission Involvement

   MRO-CRISM

   Identification of minerals associated with aqueous processes in CRISM images of Mars. Specifically, phyllosilicates are under study at Mawrth Vallis and Libya Montes, and sulfates are under study at Juventae Chasma.

   MER-A Pancam

   Identification of sulfate and phosphate minerals in the bright region salty soils at Paso Robles, Arad and Tyrone.

Publications

Bishop, J.L., Garcia, N., Dyar, M.D., Parente, M., Murad, E., Mancinelli, R.L., Drief, A. & Lane, M.D.  (2008).  Maghemite as an astrobiology indicator on the Martian surface: Reduction of iron oxides by early organic compounds to generate magnetic phases.  Geophysical Research Abstracts, 10.

Bishop, J.L., Lane, M.D., Dyar, M.D. & Brown, A.J.  (2008).  Reflectance and emission spectroscopy study of four groups of phyllosilicates: Smectites, kaolinite-serpentines, chlorites and micas.  Clay Minerals, 43:35-54.

Bishop, J.L., Lane, M.D., Dyar, M.D., Parente, M., Roach, L.A., Murchie, S.L. & Mustard, J.F.  (2008).  Sulfates on Mars: How recent discoveries from CRISM, OMEGA and the MERs are changing our view of the planet..  Goldschmidt Conf..

Bishop, J.L., McKeown, N.K., Noe Dobrea, E.Z., Ehlmann, B.L., Michalski, J.R., Milliken, R.E., Poulet, F., Mustard, J.F., Swayze, G.A., Murchie, S.L. & Bibring, J.-P.&.t.C.T.  (2008).  Phyllosilicate diversity observed by CRISM in Mawrth Vallis: Identification of nontronite, montmorillonite, kaolinite, and hydrated silica..  Lunar Planet Science Conf..

Bishop, J.L., NoeDobrea, E.Z., McKeown, N.K., Parente, M., Ehlman, B.L., Michalski, J.R., Milliken, R.E., Poulet, F., Swayze, G.A., Mustard, J.F., Murchie, S.L. & Bibring, J.-P.  (2008).  Phyllosilicate diversity and past aqueous activity revealed at Mawrth Vallis, Mars.  Science, in press(In press).

Bishop, J.L., chiffman P., S., urad E., M., D., D.M., , D.A. & , L.M.D.  (2007).  Characterization of alteration products in tephra from Haleakala, Maui: A visible-infrared spectroscopy, Mössbauer spectroscopy, XRD, EPMA and TEM study.  Clays and Clay Minerals, 55:1-17.

Lane, M.D., Bishop, J.L., Dyar, M.D., King, P.L., Parente, M. & Hyde, B.C.  (2008).  Mineralogy of the Paso Robles Soils on Mars.  American Mineralogist, 93:728-739.

Parente, M., Bishop, J.L. & Bell, J.F.  (2007).  Spectral unmixing and anomaly detection for mineral identification in Pancam images of Gusev soils.  Icarus(In review).