Thermal conductivity of porous aggregates

¹ Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
e-mail: arakawa.s.ac@m.titech.ac.jp
² Astronomical Institute, Tohoku University, Aoba, Sendai 980-8578, Japan
³ Division of Theoretical Astronomy, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan

Received: 27 October 2017
Accepted: 16 November 2017

Abstract

Context. The thermal conductivity of highly porous dust aggregates is a key parameter for many subjects in planetary science; it is not yet fully understood, however.

Aims. We investigate the thermal conductivity of fluffy dust aggregates with filling factors lower than 10^-1.

Methods. We determined the temperature structure and heat flux of the porous dust aggregates calculated through N-body simulations of static compression in the periodic boundary condition.

Results. We derive an empirical formula for the thermal conductivity through the solid network k_sol as a function of the filling factor of dust aggregates φ. The results reveal that k_sol is approximately proportional to φ², and the thermal conductivity through the solid network is significantly lower than previously assumed. In light of these findings, we must reconsider the thermal histories of small planetary bodies.