Probing Titan’s Atmosphere with ALMA
Wednesday, 17 December 2014
The advent of the Atacama Large Millimeter/Sub-millimeter Array (ALMA) has provided a new and powerful facility for probing the atmospheres of solar system targets at long wavelengths (84-720 GHz) where the rotational lines of small, polar molecules are prominent. Previously, observatories such as the Sub Millimeter Array (SMA) and IRAM (30-m and Plateau de Bure Interferometer) have demonstrated the detection of molecules such as CO, HCN, HC3N and CH3CN in Titan’s atmosphere, allowing the determination of vertical abundance gradients, and isotopic ratios of 13C/12C, 15N/14N and 18O/16O. More recently, the Herschel observatory made the first detection of hydrogen isocyanide (HNC) in Titan’s atmosphere. However, to date all these observations have not resolved Titan’s disk, and measured only disk-averaged abundances. ALMA changes this picture dramatically, since the full ALMA will eventually achieve a resolution of 0.004” at the shortest wavelengths, compared to Titan’s angular size of 0.800”. We will discuss early Titan science using ALMA, including the re-observation of species seen previously by SMA, IRAM and Herschel, and the search for new species and isotopes. We will also show the capability of ALMA to spatially map the emissions of stronger molecular species, and measure winds by using resolved spectral line profiles.