Speaker: Alain Khayat, University of Hawaii
Multi-band search for active release of volcanic gases on Mars
The study of planetary atmospheres by means of spectroscopy is important for understanding their origin and evolution. The presence of short-lived trace gases in the martian atmosphere would have implications for recent ongoing geologic activity on the planet. On Earth, sulfur dioxide (SO2), sulfur monoxide (SO) and hydrogen sulfide (H2S) are the sulfuretted gases released during volcanic outgassing. Carbonyl sulfide (OCS) is an end-product of the reactions between volcanic sulfur species and other molecules in the martian atmosphere. We carried out the first ground-based, semi-simultaneous, multi-band and mutli-species search above Tharsis and Syrtis volcanic regions on Mars. The submillimeter part of the search extended between 23 November 2011 and 13 May 2012 which corresponded to Mars’ mid Northern Spring and early Northern Summer seasons (Ls = 34–110°). The strong submillimeter rotational transitions of SO2, SO and H2S were targeted using the high-resolution heterodynce receiver Barney on the Caltech Submillimeter Telescope. The infrared part of the search covered OCS in its combination band (ν2+ν3) at 3.42 μm at two successive Mars years (31 & 32), during Mars’ late Northern Spring and mid Northern Summer seasons, between Ls= 43º and Ls= 147º. The targeted volcanic districts were observed during the two intervals, 14 Dec. 2011 to 6 Jan. 2012 on the first year, and 30 May 2014 to 16 June 2014 on the second year using the high resolution infrared spectrometer (CSHELL) on NASA’s Infrared Telescope Facility (NASA/IRTF). We reached sensitivities that are sufficient to detect a volcanic release on Mars that is 4% the SO2 released continuously from Kilauea volcano in Hawaii or 5% that of the Masaya volcano in Nicaragua. We will present our results and discuss their implications on current volcanic outgassing activity, and the volcanic/non-volcanic origin for the methane released in 2003 (Mumma et al., 2009). We will touch on future steps with the Atacama Large Millimeter Array (ALMA) that could take advantage of its unprecedented sensitivity at sub arc-second spatial resolutions on Mars, and the future European ExoMars Trace Gas Orbiter to the red planet.