LANL Abstract: Available Energy for Life on a Planet

From: Amara Graps (
Date: Fri Jan 04 2002 - 14:31:27 MST

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From: Giovanna Tinetti <>
Date: Tue, 17 Jul 2001 17:18:27 GMT (37kb)

Available Energy for Life on a Planet, with or without Stellar Radiation

Authors: L. Sertorio, G. Tinetti (University of Torino and INFN, Torino)
Comments: 30 pages, 10 figures, to be published in Nuovo Cimento C
Report-no: DFTT 33/00
Subj-class: Astrophysics; Biological Physics

     The quest for life in the Universe is often affected by the free
     use of extrapolations of our phenomenological geocentric
     knowledge. We point out that the existence of a living organism,
     and a population of organisms, requires the existence of available
     energy or, more precisely, available power per unit volume (Sect.
     1). This is not a geocentric concept, but a principle that belongs
     to the foundations of thermodynamics. A quest about availability
     in the Universe is justified. We discuss the case in which power
     comes from mining (Sect. 2), and from thermal disequilibrium
     (Sect. 3). Thermal disequilibrium may show up in two ways: on
     planets without a star (Sect. 4), and on planets where the surface
     thermal disequilibrium is dominated by the incoming photon flux
     from the nearest star (Sect. 6). In the first case we study the
     availability by simulating the structure of the planet with a
     simple model that contains the general features of the problem.
     For the first case we show that the availability is in general
     very small (Sect. 5). In the second case we show that the
     availability is in general large; the order of magnitude depends
     first of all on the star's temperature and the planet's orbit, but
     is also controlled by the greenhouse gases present on the planet.

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Amara Graps | Max-Planck-Institut fuer Kernphysik
Interplanetary Dust Group | Saupfercheckweg 1
+49-6221-516-543 | 69117 Heidelberg, GERMANY *
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