Organic Shielding of Greenhouse Gases on Early Earth

Miller, Stanley L.; Lyons, J. R.

doi:10.1126/science.279.5352.779a

Cited by 7 publications

(1 citation statement)

References 23 publications

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“…Many kinds of materials could have blocked ultraviolet radiation on the early Earth including iron in general (Olson & Pierson 1986;Pierson et al 1987), ferric oxide/oxyhydroxide (FeOx) minerals (suggested here), sulphur vapour in the atmosphere (Kasting et al 1989), a photochemical haze (Sagan & Chyba 1997;Miller et al 1998), and a combination of inorganic and prebiotic organic compounds in the oceans (Sagan 1973;Cleaves & Miller 1998;Cockell 2000). Radiation that can support photosynthesis is found from y400 to 1000 nm, although access to the entire range is not necessary.…”

Section: Introductionmentioning

confidence: 98%

Nanophase iron oxides as a key ultraviolet sunscreen for ancient photosynthetic microbes

Bishop

Louris

Rogoff

et al. 2006

International Journal of Astrobiology

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We propose that nanophase iron-oxide-bearing materials provided important niches for ancient photosynthetic microbes on the Earth that ultimately led to the oxygenation of the Earth's atmosphere and the formation of iron-oxide deposits. Atmospheric oxygen and ozone attenuate ultraviolet radiation on the Earth today providing substantial protection for photosynthetic organisms. With ultraviolet radiation fluxes likely to have been even higher on the early Earth than today, accessing solar radiation was particularly risky for early organisms. Yet, we know that photosynthesis arose early and played a critical role in subsequent evolution. Of primary importance was protection below 290 nm, where peak nucleic acid (y260 nm) and protein (y280 nm) absorptions occur. Nanophase ferric oxide/oxyhydroxide minerals absorb, and thus block, the lethal ultraviolet radiation, while transmitting light through much of the visible and near-infrared regions of interest to photosynthesis (400 to 1100 nm). Furthermore, they were available in early environments, and are synthesized by many organisms. Based on experiments using nanophase ferric oxide/oxyhydroxide minerals as a sunscreen for photosynthetic microbes, we suggest that iron, an abundant element widely used in biological mechanisms, may have provided the protection that early organisms needed in order to be able to use photosynthetically active radiation while being protected from ultraviolet-induced damage. The results of this study are broadly applicable to astrobiology because of the abundance of iron in other potentially habitable bodies and the evolutionary pressure to utilize solar radiation when available as an energy source. This model could apply to a potential life form on Mars or other bodies where liquid water and ultraviolet radiation could have been present at significant levels. Based on ferric oxide/oxyhydroxide spectral properties, likely geologic processes, and the results of experiments with the photosynthetic organisms, Euglena sp. and Chlamydomonas reinhardtii, 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.

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