Other
Scientific paper
Sep 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008epsc.conf..890l&link_type=abstract
European Planetary Science Congress 2008, Proceedings of the conference held 21-25 September, 2008 in Münster, Germany. Online a
Other
Scientific paper
The habitable zone is defined as the region around a star where a planet (or planets) would receive enough radiation from the central star (with the inclusion of a terrestrial-like model atmosphere) to maintain liquid water on its (their) surface [1]. On the terrestrial surface water was common since the very early history of the planet, and is therefore a permanent available solvent for the terrestrial biochemistry. The fact that terrestrial life is mainly based on a C = O metabolism (at least the existing one) results probably from the specific chemical characteristics of water. Nevertheless, also other solvents are able to maintain a metabolism based either C = O or on different Cmetabolisms like C = N, HN = C = NH, C = C, etc. [2]. A very promising solvent will be ammonia. It may act as coolant in water-ammonia composites and enlarges the temperature range of its liquid phase. Another quite good possibility for a solvent could be constituted by formamide. Under standard conditions, formamide will be liquid in a larger temperature range than water, namely from 273 to 495 K (0 °C to 222 °C). Moreover, formamide as solvents are able to maintain a C = O metabolism. Both compounds have already been detected in molecular clouds and seem to be very common in the outer space. The definition of the habitable zone includes water as solvent. In our work we use the concept of a "life supporting zone" to underline the fact of using other solvents than water. In our presentation first results of a life supporting zone around main sequence stars will be shown containing formamide-water and water-ammonia composites as solvents. Atmospheric effects are included by the following assumptions: (1) the planet is a grey body in the visible and a black body in the infrared region and (2) the atmosphere is black in the infrared. These first approximations allow us to simulate a greenhouse-effect. Preliminary results on the basis of water as solvent agree well with earlier calculations given in [1]. The possibility that life may grow and evolve is based on the assumption that formamide, ammonia and also different water-ammonia and water-formamide composites may exist in liquid form on extrasolar planets, when the temperature condition is fulfilled. References [1] Kasting, J. F., Whitmire D. P. and Reynolds R. T. (1993), Icarus, 101, 108-128. [2] National Research Council, NRC (2007), National Academies Press, Washington, DC 20001, ISBN 978- 0-309-10484-5.
Aittola Marko
Dvorak Rudolf
Eggl Siegfried
Eybl Veresa
Firneis Maria G.
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