L. Paganini, M. J. Mumma, G. L. Villanueva, M. A. DiSanti, B. P. Bonev, M. Lippi, H. Boehnhardt
We quantified ten parent volatiles in comet C/2009 P1 (Garradd) before
perihelion, through high-dispersion infrared spectra acquired with CRIRES at
ESO's VLT on UT 2011 August 07 (Rh = 2.4 AU) and September 17-21 (Rh = 2.0 AU).
On August 07, water was searched but not detected at an upper limit (3{\sigma})
of 2.1 \times 10^28 s-1, while ethane was detected with a production rate of
6.1 \times 10^26 s-1 (apparent mixing ratio > 2.90%). On September 17-21, the
mean production rate for water was 8.4 \times 10^28 s-1, and abundance ratios
(relative to water) of detected trace species were: CO (12.51%), CH3OH (3.90%),
CH4 (1.24%), C2H6 (1.01%) and HCN (0.36%). Upper limits (3{\sigma}) to
abundances for four minor species were: NH3 (1.55%), C2H2 (0.13%), HDO (0.89%)
and OCS (0.20%). Given the relatively large heliocentric distance, we explored
the effect of water not being fully sublimated within our FOV and identified
the 'missing' water fraction needed to reconcile the retrieved abundance ratios
with the mean values found for "organics-normal". The individual spatial
profiles of parent volatiles and the continuum displayed rather asymmetric
outgassing. Indications of H2O and CO gas being released in different
directions suggest different active vents and/or the possible existence of
polar and apolar ice aggregates in the nucleus. The high fractional abundance
of CO identifies comet C/2009 P1 as a CO-rich comet.
View original:
http://arxiv.org/abs/1202.0214
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