@article{3cff068e56be46beb14c01dda7d07c91,
title = "Evolution of H2O, CO, and CO2 production in Comet C/2009 P1 Garradd during the 2011-2012 apparition",
abstract = "We present analysis of high spectral resolution NIR spectra of CO and H2O in Comet C/2009 P1 (Garradd) taken during its 2011-2012 apparition with the CSHELL instrument on NASA's Infrared Telescope Facility (IRTF). We also present analysis of observations of atomic oxygen in Comet Garradd obtained with the ARCES echelle spectrometer mounted on the ARC 3.5-m telescope at Apache Point Observatory and the Tull Coude spectrograph on the Harlan J. Smith 2.7-m telescope at McDonald Observatory. The observations of atomic oxygen serve as a proxy for H2O and CO2. We confirm the high CO abundance in Comet Garradd and the asymmetry in the CO/H2O ratio with respect to perihelion reported by previous studies. From the oxygen observations, we infer that the CO2/H2O ratio decreased as the comet moved towards the Sun, which is expected based on current sublimation models. We also infer that the CO2/H2O ratio was higher pre-perihelion than post-perihelion. We observe evidence for the icy grain source of H2O reported by several studies pre-perihelion, and argue that this source is significantly less abundant post-perihelion. Since H2O, CO2, and CO are the primary ices in comets, they drive the activity. We use our measurements of these important volatiles in an attempt to explain the evolution of Garradd's activity over the apparition.",
keywords = "Comets, Comets, coma, Comets, composition",
author = "McKay, {Adam J.} and Cochran, {Anita L.} and DiSanti, {Michael A.} and Geronimo Villanueva and Russo, {Neil Dello} and Vervack, {Ronald J.} and Morgenthaler, {Jeffrey P.} and Harris, {Walter M.} and Chanover, {Nancy J.}",
note = "Funding Information: We thank the two anonymous reviewers whose comments improved the quality of this manuscript. This work was supported by the NASA GSRP Fellowship program through Grant No. NNX11AO03H and by the NASA Planetary Atmospheres Program through Grant No. NNX08A052G . We thank John Barentine, Jurek Krzesinski, Chris Churchill, Pey Lian Lim, Paul Strycker, and Doug Hoffman for developing and optimizing the ARCES IRAF reduction script used to reduce these data. We acknowledge the NASA-Infrared Telescope Facility for their support of our Garradd CSHELL observations and the APO observing specialists for their assistance with the Garradd ARCES observations. We would also like to acknowledge the JPL Horizons System, which was used to generate ephemerides for nonsidereal tracking of the comets during the observations, and the SIMBAD database, which was used for selection of reference stars. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Publisher Copyright: {\textcopyright} 2014 Elsevier Inc..",
year = "2015",
month = apr,
day = "1",
doi = "10.1016/j.icarus.2014.12.023",
language = "English (US)",
volume = "250",
pages = "504--515",
journal = "Icarus",
issn = "0019-1035",
publisher = "Academic Press Inc.",
}