The prospects for life on Mars: A pre-Viking assessment

Sagan, Carl; Lederberg, Joshua

doi:10.1016/0019-1035(76)90039-7

Cited by 27 publications

(9 citation statements)

References 37 publications

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“…According to photographs obtained by orbital missions around Mars, a pre-Viking assessment was made on the potential for habitable conditions and organic life on the planet (Sagan and Lederberg 1976). Since the successful landing of Viking 1 on Mars in 1976, mankind began to search for life on the planet's surface.…”

Section: Introductionmentioning

confidence: 99%

Gypsum in modern Kamchatka volcanic hot springs and the Lower Cambrian black shale: Applied to the microbial-mediated precipitation of sulfates on Mars

Tang

Ehreiser

2014

American Mineralogist

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Gypsum is a mineral that commonly precipitates in hydrothermal environments. This study reports the electron microscopic analyses of gypsum morphologies and crystal sizes found in hot springs on the Kamchatka Peninsula, Russia, and compares these analyses with gypsum morphologies of hydrothermal genesis found in Lower Cambrian black shale. In sediments of the Kamchatka hot springs, we observed prismatic, prismatic pseudo-hexagonal, fibrous, tubular, lenticular and twinned gypsum crystals, with crystal sizes ranging from <200 nm to >200 mm. The coexistence of diverse crystal habits of gypsum implies a constant interaction between hot spring geochemistry and the metabolisms of the microbial community. The crystallization of Ca-and Ba-sulfates in the black shale of the Lower Cambrian, which shows similar but less varied morphology, was influenced by post-depositional hydrothermal fluids. The partial replacement of pyrite by sulfates in a situation coexisting with rich biomass deposits and animal fossils indicates limited modification of the sedimentary records by biological materials. If the gypsum precipitated on Mars underwent similar interactions between microbial communities and their geochemical environments, the resulting crystal habits could be preserved even better than those on Earth due to the weak geodynamics prevailing on Mars throughout its evolutionary history.

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Section: Introductionmentioning

confidence: 99%

Gypsum in modern Kamchatka volcanic hot springs and the Lower Cambrian black shale: Applied to the microbial-mediated precipitation of sulfates on Mars

Tang

Ehreiser

2014

American Mineralogist

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“…The combination of water and volcanic heat provides a key precursory condition for biotic development (e.g. Sagan & Lederberg 1976). Therefore, understanding the distribution, ages and formation conditions of these features is of critical significance in guiding future exploration strategies, in terms of both the search for extraterrestrial life and a future human presence on Mars.…”

mentioning

confidence: 99%

Rootless cones on Mars: a consequence of lava-ground ice interaction

Fagents

Lanagan

Greeley

2002

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Fields of small cratered cones on Mars are interpreted to have formed by rootless eruptions due to explosive interaction of lava with ground ice contained within the regolith beneath the flow. Melting and vaporization of the ice, and subsequent explosive expansion of the vapour, act to excavate the lava and construct a rootless cone around the explosion site. Similar features are found in Iceland, where flowing lavas encountered water-saturated substrates. The martian cones have basal diameters of c. 30-1000m and are located predominantly in the northern volcanic plains. High-resolution Mars Orbiter Camera images offer significant improvements over Viking data for interpretation of cone origins. A new model of the dynamics of cone formation indicates that very modest amounts of water ice are required to initiate and sustain the explosive interactions that produced the observed features. This is consistent with the likely low availability of water ice in the martian regolith. The scarcity of impact craters on many of the host lava flows indicates very young ages, suggesting that ground ice was present as recently as <10-100Ma, and may persist today. Rootless cones therefore act as a spatial and temporal probe of the distribution of ground ice on Mars, which is of key significance in understanding the evolution of the martian climate. The location of water in liquid or solid form is of great importance to future robotic and human exploration strategies, and to the search for extraterrestrial life.

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“…In a pre-Viking assessment of the possibility of life on Mars, Sagan and Lederberg (1976) argued that liquid water is the most stringent limiting factor for life on Mars. They suggested that the low oxygen partial pressure would be a negligible impediment to life and that the ultraviolet flux could have been countered by living below the surface or by developing an ultraviolet-absorbing exoskeleton or shield (that might also be able to conserve water).…”

Section: Possible Photosynthetic Niches On Marsmentioning

confidence: 99%

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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The prospects for life on Mars: A pre-Viking assessment

Cited by 27 publications

References 37 publications

Gypsum in modern Kamchatka volcanic hot springs and the Lower Cambrian black shale: Applied to the microbial-mediated precipitation of sulfates on Mars

Gypsum in modern Kamchatka volcanic hot springs and the Lower Cambrian black shale: Applied to the microbial-mediated precipitation of sulfates on Mars

Rootless cones on Mars: a consequence of lava-ground ice interaction

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

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