Christopher Howard

“Crystallographic, ab initio and spectroscopic properties of planetary ices in the outer solar system.”

PhD project title:

Properties of planetary ices formed in the NH3 – CO2 ± H2O ternary system.

Project description:

Interactions between the most simple of molecules are of fundamental interest across diverse areas of the physical sciences, and the ternary system H2O – NH3 – CO2 is no exception. 

In the outer solar system, interaction of CO2 with aqueous ammonia is likely to occur, synthesizing ‘rock-forming’ minerals, with CO2 also playing a major role 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.

However, 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 solids and fluids in planetary environments. 

This project will focus on both computation and experimental data, specifically to acquire thermal, structural, elastic and vibrational properties in preparation for a planetary model. The hydrogen-bonded nature of this system makes neutron diffraction ideal over X-ray diffraction, giving accurate atomic positions and therefore bonding, critical for material properties. On-going and future work will provide new insights into the behaviour of NH3 – CO2 ± H2O solids and fluids in planetary environments.