Acoustic and Microstructural Properties of Partially Molten Samples in the Ice–Ammonia System

Abstract

We measured the ultrasonic properties and microstructure of two-phase binary mixtures of the ice−ammonia partial melt system, which was selected based on its importance for numerous planetary bodies. The equilibrium microstructure of ice−ammonia melt was examined using a light microscope within a cold room. The measured median dihedral angle between the solid and melt at 256 K is approximately 63°, with a broad distribution of observed angles between 10° and 130°. P-wave velocities in the partially molten samples were measured as a function of temperature (177 < T(K) < 268) and composition (1−6.4 wt % NH3). Vp decreases approximately linearly with increasing temperature and melt fraction. We compare the results of this study to those of other potential binary systems by normalizing the datasets using a vertical lever (TL−TE) and articulating the potential effects on the mechanical behavior and transport capabilities of partially molten ice in icy satellites.

Keywords

• ice
• ammonia
• partial melt
• microstructure
• ultrasonics