Photolysis Study of Cosmic Ices and Proposed Reflectance Measurements

We have carried out laboratory simulation studies on the spectral identification of IR absorption features produced through vacuum ultraviolet photon-induced chemical reactions in several ice systems relevant to icy satellites of planetary systems and grains in interstellar medium. Several ice systems containing some of the most abundant molecules, namely, H2O, CH4, CO, CO2, CH3OH, and NH3, in cosmic environments are studied. We have also measured the production yields for the photolyzed products and the destruction yields of the parent molecules in the ice samples. A tunable intense synchrotron radiation light source available at the National Synchrotron Radiation Research Center, Hsinchu, Taiwan, was employed to provide the required photons. Typical photon-induced reaction products include radicals (CH2, CH3, C2H3, C2H5), light hydrocarbons (C2H2, C2H4, C2H6, C3H8), carbon-containing compounds (suboxides), alcohols (CH3OH, C2H5OH), and others like HCO, H2CO, XCN, and simple amino acids. In addition to the ongoing simulation studies we plan to implement an in-situ reflectance measurement of a given ice sample before and after photolysis in the spectral region between 0.3 and 2.5 micron. The chosen samples will be relevant to surface materials of our Solar System. The results to be obtained will provide valuable data to our understanding of space weathering for the surfaces of airless bodies of our Solar System. Detailed results of our ongoing work and the proposed implementation will be presented. This research is based on work supported by NSF grant AST-0604455.