(i) UV irradiation of ices and isotope fractionation
Studies of icy objects in the Solar System such as comets and Saturn’s frozen satellites have shown how important it is to understand interactions between gas phases and ice surfaces in conditions of the nascent Solar System. Remarkably, the on-going detection of argon degassed by Comet 67P and studied by the Rosetta spacecraft highlights the necessity to document the behaviour of volatile elements such as noble gases in the cold environment. We shall develop a new experimentation in which various ices will be grown up onto a cold head in the presence of noble gases and/or nitrogen. The ice will be heated at different temperatures, and the released noble gases will be analyzed in situ by static mass spectrometry.
(ii) Xenon photochemistry and isotope fractionation
To supplement experiments done with the synchrotron light (Task 2), we shall explore Xe photochemistry under Lyman alpha irradiation, one of the best analogues of the solar light. Experiments will consist in irradiating with a Ly-alpha lamp a cold surface made of Xe trapped in water-ice, and attempt to form Xe hydrides and oxides. In the Archean atmosphere such compounds could be then lifted off the atmosphere following Coulomb entrainment by escaping H+ ions also from H2O photodissociation. Noble gas (Xe) and stable isotopes (H, O) will be analyzed at CRPG.