|Confirmation of the first detection of HNC on Titan
|Observations of Titan were performed on June 14, 2010 with Herschel-HIFI, as part of the Herschel guaranteed time key programme Water and related chemistry in the Solar System (PI: P. Hartogh). These measurements, targetted to the H2O 556.935 GHz line, have shown in addition an unanticipated line at 543.897 GHz. We attribute this emission to HNC(6-5), which would represent the first detection of HNC in Titan.s atmosphere. Preliminary interpretation of the data suggests that HNC is confined to the upper atmosphere (above at least 300 km, and may be even higher). HNC is a plausible species in Titan.s atmosphere, expected to be produced by dissociative recombination reaction of the ionospheric ion HCNH+ at altitudes above 1000 km. The loss process considered is HNC protonation by reaction with H-bearing ions and H atoms, yielding HCN. An accurate knowledge of the vertical distribution of HNC and HCN at altitudes above 800 km would provide a major constraint for the photochemical formation scheme of HNC. The goal of this proposal are (i) to spectroscopically confirm the presence of HNC in the upper atmosphere of Titan by observing another transition at 906 GHz (ii) to measure the narrow component of HCN at 532 GHz, in order to retrieve its abundance abundance profile over 400-800 km. The so-constrained HNC-HCN ratio in the upper atmosphere will permit us to discriminate between the different possible formation-loss schemes of HNC.
|Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
|Publisher And Registrant
|European Space Agency
|European Space Agency, 2012, OT1_rmoreno_1, SPG v14.1.0. https://doi.org/10.5270/esa-rb4o2cr