Effects of insoluble particles on grain growth in polycrystalline ice: Implications for rheology of ice shells of icy satellites

Effects of small volume fractions of insoluble particles on grain growth rates of polycrystalline ice were examined at 270 K. The presence of approximately 1 vol% of insoluble particles significantly inhibits the grain growth, and this inhibition effect strongly depends on the particle size. The observed grain growth behavior of ice can be reasonably interpreted on the basis of the Zener pinning effect. Our preliminary results suggest that low viscosities due to small grain sizes required for convective instability in ice shells of icy satellites are achieved by the presence of very small fractions of fine silicate dust particles.