Detection of C2HD and the D/H ratio on Titan |
| |
Authors: | Athena Coustenis,Donald E. Jennings,Yves Bé nilan,Sandrine Vinatier,Gordon L. Bjoraker,Ronald C. Carlson |
| |
Affiliation: | a Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique (LESIA), Observatoire de Paris-Meudon, 5, Place Jules Janssen, 92195 Meudon Cedex, France b NASA/Goddard Space Flight Center, Code 693, Greenbelt, MD 20771, USA c LISA, CNRS, Univ. Paris 12 and Paris 7, 94010 Créteil Cedex, France d Department of Astronomy, University of Maryland, College Park, MD 20742, USA e IACS, Catholic University of America, and NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA |
| |
Abstract: | We report here the first detection of mono-deuterated acetylene (acetylene-d1, C2HD) in Titan's atmosphere from the presence of two of its emission bands at 678 and 519 cm−1 as observed in CIRS spectral averages of nadir and limb observations taken between July 2004 and mid-2007. By using new laboratory spectra for this molecule, we were able to derive its abundance at different locations over Titan's disk. We find the C2HD value () to be roughly constant with latitude from the South to about 45° N and then to increase slightly in the North, as is the case for C2H2. Fitting the 678 cm−1ν5 band simultaneously with the nearby C2H2 729 cm−1ν5 band, allows us to infer a D/H ratio in acetylene on Titan with an average of the modal values of 2.09±0.45×10−4 from the nadir observations, the uncertainties being mainly due to the vertical profile used for the fit of the acetylene band. Although still subject to significant uncertainty, this D/H ratio appears to be significantly larger than the one derived in methane from the CH3D band (upper limit of 1.5×10−4; Bézard, B., Nixon, C.A., Kleiner, I., Jennings, D.E., 2007. Icarus, 191, 397-400; Coustenis, A., Achterberg, R., Conrath, B., Jennings, D., Marten, A., Gautier, D., Bjoraker, G., Nixon, C., Romani, P., Carlson, R., Flasar, M., Samuelson, R.E., Teanby, N., Irwin, P., Bézard, B., Orton, G., Kunde, V., Abbas, M., Courtin, R., Fouchet, Th., Hubert, A., Lellouch, E., Mondellini, J., Taylor, F.W., Vinatier, S., 2007. Icarus 189, 35-62). From the analysis of limb data we infer D/H values of (at 54° S), (at 15° S), (at 54° N) and (at 80° N), which average to a mean value of 1.63±0.27×10−4. |
| |
Keywords: | Titan Atmospheres, composition Infrared observations Satellites, atmospheres Satellites, composition |
本文献已被 ScienceDirect 等数据库收录! |
|