Uncorrelated Volatile Behavior during the 2011 Apparition of Comet C/2009 P1 Garradd
Abstract
The High Resolution Instrument Infrared Spectrometer (HRI-IR) on board the Deep Impact Flyby spacecraft detected H2O, CO2, and CO in the coma of the dynamically young Oort Cloud comet C/2009 P1 (Garradd) post-perihelion at a heliocentric distance of 2 AU. Production rates were derived for the parent volatiles, Q H2O = 4.6 ± 0.8 × 1028, Q CO2 = 3.9 ± 0.7 × 1027, and Q CO = 2.9 ± 0.8 × 1028 molecules s-1, and are consistent with the trends seen by other observers and within the error bars of measurements acquired during a similar time period. When compiled with other observations of Garradd's dominant volatiles, unexpected behavior was seen in the release of CO. Garradd's H2O outgassing, increasing and peaking pre-perihelion and then steadily decreasing, is more typical than that of CO, which monotonically increased throughout the entire apparition. Due to the temporal asymmetry in volatile release, Garradd exhibited the highest CO to H2O abundance ratio ever observed for any comet inside the water snow line at ~60% during the HRI-IR observations. Also, the HRI-IR made the only direct measurement of CO2, giving a typical cometary abundance ratio of CO2 to H2O of 8% but, with only one measurement, no sense of how it varied with orbital position.
- Publication:
-
The Astronomical Journal
- Pub Date:
- January 2014
- DOI:
- 10.1088/0004-6256/147/1/24
- arXiv:
- arXiv:1311.4802
- Bibcode:
- 2014AJ....147...24F
- Keywords:
-
- comets: general;
- comets: individual: C/2009 P1 Garradd;
- infrared: planetary systems;
- techniques: spectroscopic;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 38 pages, 10 figures, 5 tables, accepted for publication in The Astronomical Journal