Manfroid, Jean[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO) >]
Hutsemekers, Damien[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Arpigny, Claude[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO) >]
Boissier, J.[IRAM, 300 rue de la Piscine, Domaine Universitaire, F-38406 Saint Martin d'Hères, France.]
Cochran, W.[Department of Astronomy and McDonald Observatory, University of Texas at Austin, C-1400, Austin, TX 78712.]
Colom, P.[LESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92190 Meudon, France; .]
Crovisier, J.[LESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92190 Meudon, France; .]
Milutinovic, N.[University of Victoria - UVic > Department of Physics and Astronomy >]
Moreno, R.[LESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92190 Meudon, France; .]
Prochaska, J. X.[Department of Astronomy and Astrophysics, and UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064.]
Ramirez, I.[Department of Astronomy and McDonald Observatory, University of Texas at Austin, C-1400, Austin, TX 78712.]
Schulz, R.[ESA/RSSD, ESTEC, P.O. Box 299, NL-2200 AG Noordwijk, The Netherlands.]
Zucconi, J.-M.[Observatoire de Besançon, F-25010 Besançon Cedex, France.]
[en] Comets: General ; comets: individual (17P/Holmes) ; Radio Lines: Solar System
[en] From millimeter and optical observations of the Jupiter-family comet 17P/Holmes performed soon after its huge outburst of 2007 October 24, we derive [SUP]14[/SUP]N/[SUP]15[/SUP]N = 139 +/- 26 in HCN and [SUP]14[/SUP]N/[SUP]15[/SUP]N = 165 +/- 40 in CN, establishing that HCN has the same nonterrestrial isotopic composition as CN. The same conclusion is obtained for the long-period comet C/1995 O1 (Hale-Bopp) after a reanalysis of previously published measurements. These results are compatible with HCN being the prime parent of CN in cometary atmospheres. The [SUP]15[/SUP]N excess relative to the Earth's atmospheric value indicates that N-bearing volatiles in the solar nebula underwent important N isotopic fractionation at some stage of solar system formation. HCN molecules never isotopically equilibrated with the main nitrogen reservoir in the solar nebula before being incorporated in Oort Cloud and Kuiper Belt comets. The [SUP]12[/SUP]C/[SUP]13[/SUP]C ratios in HCN and CN are measured to be consistent with the terrestrial value.
[LESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92190 Meudon, France; .]
