《《Monte Carlo modeling of the thermal conductivity of porous cometary ice》.pdf

Icarus 157, 219–227 (2002) doi:10.1006/icar.2002.6815, available online at on Monte Carlo Modeling of the Thermal Conductivity of Porous Cometary Ice Yossi Shoshany, Dina Prialnik, and Morris Podolak Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv 69978, Israel E-mail: dina@planet.tau.ac.il Received July 1, 2001; revised November 13, 2001 We should stress that pores will be assumed to be empty, The basic structure of comet nuclei is an aggregation of grains, whereas in reality, when the solid matrix is made predominantly with a size distribution that extends over several orders of magni- of ice and temperatures are not too low, vapor may fill the pores tude and a similar distribution of pores. Although attempts have and flow through them. Such is the case in the outer layers of been made to assess the effect of porosity on the thermal conductiv- cometary nuclei, for example. Often, heat transport by vapor ity, the effect of pore size distribution has been ignored. Modeling can be more efficient than heat conduction by the solid (e.g., a porous structure with a wide size distribution would require a Smoluchowski 1982, Steiner and K¨omle 1991). Rigorously, such very fine 3-D grid, so as to accommodate the smallest and largest situations should be described by simultaneous solutions of the voids. In order to circumvent this difficulty, we adopt a hierarchical