Experimental studies of hydrated analogue materials of relevance to Solar System bodies using synchrotron radiation

Abstract

Synchrotron X-ray powder diffraction on beamline I11 at the Diamond Light Source is used to study the in situ formation of CO2/CH4 clathrates. Frozen aqueous salt solutions were subjected to gas pressures between 5-26 bar and thermally cycled in the temperature range 90-270 K. This was done to replicate the likely sub-surface ocean compositions and pressures found on Europa, Enceladus and Titan and the Martian cryosphere. By using varying composition and concentration of the salt solutions we measure their inhibiting effect on clathrate formation, and in some cases find that the salts can affect the clathrate structure.

Synchrotron X-ray powder diffraction and in situ Raman spectroscopy are used to observe the change in structure of epsomite as it is cycled through a range of temperatures replicating diurnal and seasonal changes on the Martian surface. We find no evidence to support a low temperature phase of epsomite which would be the more prevalent form on colder surfaces.

Results are presented on the study of in situ synchrotron X-ray powder diffraction on meridianiite formation. A slow cooling rate was applied to the sample using a cold cell on I11's Long Duration Experiment facility; in situ cooling experiments were also performed on I11s time- resolved facility. Large ice crystals which then break
into smaller particles as meridianiite forms were observed and the implications for ice rheology are discussed. A sample simulating Europa's ocean composition was also investigated in the same Long Duration Experiment. It is shown that meridianiite seemingly prevents gypsum forming at low temperatures, which has implications for organic material beneath the surface of Europa.