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2008 Annual Science Report

SETI Institute Reporting  |  JUL 2007 – JUN 2008

Iron, the Oxygen Transition, UV Shielding, and Photosynthesis

Project 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.

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

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.

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