The Volatile Composition of Comet C/2003 K4 (Linear) at Near-Ir Wavelengths—comparisons With Results From the Nançay Radio Telescope and From Theodin,spitzer, Andsohospace Observatories

We observed comet C/2003 K4 (LINEAR) using NIRSPEC at the Keck Observatory on UT 2004 November 28, when the comet was at 1.28 AU from the Sun (post-perihelion) and 1.38 AU from Earth. We detected six gaseous species (H 2 O, OH*, C 2 H 6 , CH 3 OH, CH 4 , and HCN) and obtained upper limits for three others (H 2 CO, C 2 H 2 , and NH 3 ). Our results indicate a water production rate of (1.72 ± 0.18) × 10 29 molecules s −1 , in reasonable agreement with production rates from SOHO (on the same day), Odin (one day earlier), and Nançay (about two weeks earlier). We also report abundances (relative to water) for seven trace species: CH 3 OH (∼1.8%), CH 4 (∼0.9%), and C 2 H 6 (∼0.4%) that were consistent with mean values among Oort cloud (OC) comets, while NH 3 (<0.55%), HCN (∼0.07%), H 2 CO (<0.07%), and C 2 H 2 (<0.04%) were "lower" than the mean values in other OC comets. We extracted inner-coma rotational temperatures for four species (H 2 O, C 2 H 6 , CH 3 OH, and CH 4 ), all of which are consistent with 70 K (within 1 σ ). The extracted ortho-para ratio for water was 3.0 ± 0.15, corresponding to spin temperatures larger than 39 K (at the 1 σ level) and agreeing with those obtained with the Spitzer Space Telescope at the 2 σ level.