We report simple measurements of the physical properties of frozen aqueous solutions of NH3 down to 80 K. These measurements are relevant for the geophysics of icy satellites and Titan in particular. We find that the thermal conductivity of NH3-rich (~10--30%) water ice is 1--2 Wm-1 K-1, or 2--3 times lower than that of pure water ice. We find evidence for significant microwave absorptivity in NH3-rich ice-even at 100K-and that the electrical properties are very strongly temperature-dependent. At around 100K the Young's Modulus for NH3-free and NH3-rich ice appears to be about the same, while at 160K the NH3-rich ice is 10¿ more compliant. ¿ 2001 American Geophysical Union