Infrared study of lower sulfur oxides on Io's surface
Sulfur dioxide, SO2, and sulfur monoxide, SO, are the only sulfur oxides that have been firmly identified in Io's atmosphere. While SO2, according to infrared observations, is ubiquitous on Io's surface and seems to widely dominate it, SO has never been found on the surface. In fact, contrary to SO2, SO is extremely reactive and unstable. It decomposes by disproportionation forming SO2 and S2O. This latter molecule, disulfur monoxide, is much more stable than SO and, depending on temperature and pressure conditions, it can, either, directly condense on the "cold" surface, or polymerize forming polysulfuroxides, or even, thermally decompose to SO2 and sulfur.Hapke (1989, Icarus 79, 47-74) measured the spectral reflectance of S2O and its resulting polymer over the range 200-1700 nm. Using Voyager observations, he tried to show that the spectral properties of Io can be matched by combinations of SO2, S2O, polysulfuroxide and basalt, but his model was controversial and since then, no experimental data on S2O and its polymer were added to confirm or definitely reject the possibility of the presence of these molecules on Io's surface. Thus, we have undertaken series of laboratory experiments to synthesize and measure the infrared spectra of S2O and its resulting polymeric sulfuroxides, under different temperature conditions and very low pressures. The results of these experiments will be presented and compared to NIMS/Galileo data. Then, the way of formation and possible presence of these lower sulfur oxides on Io's surface will be discussed.
AAS/Division for Planetary Sciences Meeting Abstracts #36
- Pub Date:
- November 2004