Abstract
The sublimation temperature of the cometary nucleus essentially depends on the vapor pressure and the latent heat of the most volatile material available in abundance at the surface of the nucleus. This sublimation temperature sets in turn the characteristic distance ro separating the sublimation steady state (small dependence on distance) from the radiation steady state (steep dependence on distance). ro can therefore be used, not only as a measure of the surface temperature of the nucleus, but also as an identification of the nature of the prevailing snow. Three techniques to measure ro are described here. Two have given significant results because they can cover large ranges of distances: The dependence on distance of the Non Gravitational Forces suggests that the short period comets f sublimations are controlled by water snow only; the light curves of “new” comets concur to the same conclusion. Among all the comets studied so farnone seems to be controlled by anything more volatile than water snow or ice. The large production rates of H and OH observed in cometary atmospheres suggest that they come from the dissociation of H2O in the vapor state. The theory of vaporization only is able to close the gap: it concludes that this water vapor was indeed released by the sublimation of water ice.
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Delsemme, A.H. (1985). The Sublimation Temperature of the Cometary Nucleus: Observational Evidence for H2O Snows. In: Klinger, J., Benest, D., Dollfus, A., Smoluchowski, R. (eds) Ices in the Solar System. NATO ASI Series, vol 156. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-5418-2_24
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DOI: https://doi.org/10.1007/978-94-009-5418-2_24
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