Physical properties of ammonia‐rich ice: Application to Titan

Abstract

Abstract. 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 (-0 10-30%) water ice is 1-2 Wm-iK -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 10x more compliant.

Arecibo radar observations of Rhea, Dione, Tethys, and Enceladus

“…Lowering of the melting point in these objects is one means of explaining the evidence of more active geology than would otherwise be expected on these small, cold objects (Squyres et al, 1983). Ammonia in the near-surface should affect the radar reflectivity since it can increase the absorption of centimeter-wavelength radiation considerably (Lorenz and Shandera, 2001) and be less optically active than silicates or organics. To date there has been no robust detection of any significant quantity of ammonia on these objects.…”

Titan's damp ground: Constraints on Titan surface thermal properties from the temperature evolution of the Huygens GCMS inlet

“…Solid and liquid organic materials tend to have 0.2 < k < 0.3 Wm −1 K −1 , thus a tar (the "crème brulee hypothesis") seems incompatible with the observed temperature history. Solid ice at 94 K has a conductivity of ~5 Wm −1 K −1 , while solid ammonia-rich ice has a conductivity of ~2 Wm −1 K −1 (Lorenz and Shandera 2001). Clathrate hydrates or ices like CO 2 tend to have k < 1 Wm −1 K −1 , e.g., Ross and Kargel (1998).…”

Heat flow and depth to a possible internal ocean on Triton

“…There are some available measures of the thermal conductivity of ammonia-rich ice (Ross and Kargel, 1998;Lorenz and Shandera, 2001). It can be deduced from these measurements that the thermal conductivity of …”