Snow and Ice Environments

Fritsen, Christian H.

doi:10.1002/0471263397.env281

Cited by 1 publication

(1 citation statement)

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“…We also included in Table 7 the calculated chemical composition of Earth seawater at 220°C (lower temperature limit for biological activity) to demonstrate the powerful influence of freezing on chemical composition. According to model calculations, by the time the temperature has dropped to 220°C, ice, calcite, and mirabilite are precipitating; of the original water, 87.6% has pre- Broad-scale Kennedy (1993), Simmons et al (1993), Ellis-Evans (1996), Vincent and James (1996), reviews Psenner and Sattler (1998), Hoover and Gilichinsky (2001), Fritsen (2002) Lake Vostok, Ellis-Evans and Wynn-Williams (1996), Kapitsa et al (1996), Jouzel et al (1999), Karl et al Antarctica (1999), Nadis (1999), Priscu et al (1999), Vincent (1999), Price (2000), Duxbury et al (2001) Other cold lakes Matsumoto (1993), Marion (1997), Fritsen andPriscu (1998, 1999), Kepner et al (1998), Priscu et al (1998), Junge et al (2004) Sea ice Helmke and Weyland (1995), Arrigo et al (1997), Bowman et al (1997), Brown (1997), Hawes et al (1999), Nadeau and Castenholz (2000), Junge et al (2001), Thomas andDieckmann (2002) Permafrost Gilichinsky et al (1993), Soina et al (1995), Stone (1999), Rivkina et al (2000), Hoover and Gilichinsky (2001),…”

Section: The Brine Oceanmentioning

confidence: 99%

The Search for Life on Europa: Limiting Environmental Factors, Potential Habitats, and Earth Analogues

et al. 2003

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The putative ocean of Europa has focused considerable attention on the potential habitats for life on Europa. By generally clement Earth standards, these Europan habitats are likely to be extreme environments. The objectives of this paper were to examine: (1) the limits for biological activity on Earth with respect to temperature, salinity, acidity, desiccation, radiation, pressure, and time; (2) potential habitats for life on Europa; and (3) Earth analogues and their limitations for Europa. Based on empirical evidence, the limits for biological activity on Earth are: (1) the temperature range is from 253 to 394 K; (2) the salinity range is a(H2O) = 0.6-1.0; (3) the desiccation range is from 60% to 100% relative humidity; (4) the acidity range is from pH 0 to 13; (5) microbes such as Deinococcus are roughly 4,000 times more resistant to ionizing radiation than humans; (6) the range for hydrostatic pressure is from 0 to 1,100 bars; and (7) the maximum time for organisms to survive in the dormant state may be as long as 250 million years. The potential habitats for life on Europa are the ice layer, the brine ocean, and the seafloor environment. The dual stresses of lethal radiation and low temperatures on or near the icy surface of Europa preclude the possibility of biological activity anywhere near the surface. Only at the base of the ice layer could one expect to find the suitable temperatures and liquid water that are necessary for life. An ice layer turnover time of 10 million years is probably rapid enough for preserving in the surface ice layers dormant life forms originating from the ocean. Model simulations demonstrate that hypothetical oceans could exist on Europa that are too cold for biological activity (T < 253 K). These simulations also demonstrate that salinities are high, which would restrict life to extreme halophiles. An acidic ocean (if present) could also potentially limit life. Pressure, per se, is unlikely to directly limit life on Europa. But indirectly, pressure plays an important role in controlling the chemical environments for life. Deep ocean basins such as the Mariana Trench are good analogues for the cold, high-pressure ocean of Europa. Many of the best terrestrial analogues for potential Europan habitats are in the Arctic and Antarctica. The six factors likely to be most important in defining the environments for life on Europa and the focus for future work are liquid water, energy, nutrients, low temperatures, salinity, and high pressures.

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