Comparative Planetology
Planetary ices in the H2O – NH3 – CO2 ternary system
Christopher Howard
Dr. Dominic Fortes (UCL)
Interactions between the most simple of molecules are of fundamental interest across diverse areas of the physical sciences, as well as underpinning a number of important industrial processes, and the ternary system H2O – NH3 – CO2 is no exception.
Interaction of CO2 with aqueous ammonia in the outer solar system is likely to occur, synthesizing ‘rock-forming’ minerals in the outer solar system (Kargel, 1991), with CO2 playing a major role (as a dissolved volatile) in ammonia-water oceans and cryomagmas inside icy planetary bodies. In the same context, ammonium carbonates may have some astrobiological relevance, since removal of water leads to the formation of urea.
Our knowledge of ammonium carbonates is limited under ambient conditions of pressure and temperature and is entirely absent at the higher pressures extant in the interiors of large icy bodies, limiting our ability to model the behaviour of H2O – NH3 – CO2 solids and fluids in planetary environments. To solve this, computational and experimental mineral physics techniques have been (and will be) used to determine the structure and properties of solid ammonium carbonates applicable to these bodies.
So far, neutron powder diffraction of a known compound, ammonium carbamate, has yielded thermal and structural measurements, and computational calculations of ammonium carbonate have provided elastic, thermal and vibrational properties, in preparation for a planetary model.
Ongoing and future work will concentrate on the development of a planetary model that will provide new insights into the behaviour of H2O – NH3 – CO2 solids and fluids in planetary environments.


16:30 - 18:00