Mathematics – Logic
Scientific paper
Sep 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996dps....28.0426k&link_type=abstract
American Astronomical Society, DPS meeting #28, #04.26; Bulletin of the American Astronomical Society, Vol. 28, p.1075
Mathematics
Logic
Scientific paper
It is generally accepted that the small icy bodies of the Solar System - comets, icy satellites and transneptunian Kuiper-belt objects have been formed following an accretional path starting with dust and going through the fluffy aggregate stage and then planetesimals. Such a mechanism of formation involves different internal processes developing within a forming body. The effects considered heare are (i) gravitational self-compaction of the body, (ii) radioactive heat generation, and (iii) heat conduction. The radioactive heating acts very slow due to decay of the nuclei K40, Th232, U235 and U238. On the other hand, the nuclei Al26 have a short lifetime tau ~ 10(6) years. This is a value comparable to the time interval required for a satellite formation. Its role as a fast internal source of heat could be important especialy for the small bodies for which the specific gravitational energy is negligible. Indeed, a ratio of the total energy of radioactive decay to the total gravitational energy is of the order (HM)/(0.6GM(2) /R) ~ R(-2) where M is the mass, R is the radius, G is the gravitational constant and H is radioactive energy stored in the unit of mass. In this paper we analyze, on the basis ot the low-temperature, megapascal-pressure experimental data, the self-compaction of icy satellites due to temperature-, pressure- and time-dependent rheological processes. The presented considerations are the extension of those presented in our previous publications on the subject (Proc. XVIII LPSC, PEPI 55, and PSS 41, 42, 43). Now, the main emphasis is put on the role of the presence of Al26. However, we include also the discussion of the influence of different rheologies (especially taking into account the presence of ammonia admixture in water ice) on the results obtained. The numerical results are mainly for small Saturnian satellites Janus and Epimatheus. A special series of calculations have been performed in order to compare our model with those of Prialnik and Podolak (Icarus 1995) concerning icy objects dozen kilometers in size.
Kossacki Konrad J.
Leliwa-Kopystyński Jacek
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