Comparative Planetary Science
Water Production Rates of the Oort Cloud and Jupiter Family Comets Observed by Herschel/SPIRE
Thomas G. Wilson
Bruce Swinyard (University College London, RAL Space), Jonathan Rawlings (University College London)
University College London
Water is a main constituent of cometary comae, and multi-band infrared and submillimetre spectroscopy of fundamental rotational water lines is an important tool in studying the physical properties of comae. Here we present all Herschel/SPIRE spectroscopic observations of several fundamental rotational ortho- and para-water transitions seen in the Jupiter Family comets; 103P/Hartley 2, 10P/Tempel 2, and 45P/Honda-Mrkos-Pajdusakova, and the Oort Cloud comet; C/2009 P1 (Garradd). Radiative transfer models which include excitation by collisions with neutrals and electrons, and solar infrared radiation were used to produce synthetic line profiles. We constrain the ortho-to-para ratio (OPR) for all comets and by constraining the electron density profile, and estimating the gas kinetic temperature and the gas expansion velocity, we derive water production rates for the four comets noted above; ∼2-9×10^27 s^-1, ∼2-12×10^27 s^-1, ∼0.2-1.4×10^27 s^-1, and ∼7-26×10^28 s^-1. Comparisons are made with the water production rates derived using an OPR of 3.
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