|HCl, HF and H2O+ in comets : probing solar nebula and coma chemistry
|The composition of comets provides a record of the chemistry of the primitive solar nebula, in the region and at the time of their formation. The presence of interstellar-like organics and other exotic gases in cometary nuclei gives the definite impression that comets preserve a record of the interstellar composition characteristic of the presolar cloud, or that cometary and interstellar molecules formed by similar processes. We propose to take benefit of the unique capacities of Herschel in the sub-millimeter domain and the high sensitivity of HIFI to search for cometary molecules of cosmogonic interest that cannot be observed from the ground, namely HCl (both (35)Cl and (37)Cl isotopes) and HF. These species are the main reservoirs of fluorine and chlorine in the ISM, as measured from Herschel, and are locked onto grains in dense molecular clouds. Their survival during the collapse of the presolar cloud is uncertain, but both HCl and HF should have reformed readily from the released atomic Cl and F in the proto-planetary disk. We expect that these molecules condensed onto pre-cometary grains during the cooling phase of the Solar Nebula. In addition, observations of H2O+ are proposed to constrain the H2O chemistry in cometary atmospheres and to measure accurately the frequency of its 111-000 and 202-111 ortho transitions near 1115 and 742 GHz, respectively, for best interpretation of H2O+ interstellar data.
|Searches for HCl and HF in comets 103P-Hartley 2 and C-2009 P1 (Garradd) with the Herschel Space Observatory . Bockelée-Morvan D. et al. . Astronomy & Astrophysics, Volume 562, id.A5, 8 pp. . 562 . 10.1051/0004-6361/201322939 . 2014A&A...562A...5B ,
|HIFI_HifiPoint_fs, HIFI_HifiPoint_dbs, HIFI_HifiMapping_fly
|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_dbockele_1, SPG v14.1.0. https://doi.org/10.5270/esa-nxm5pa7