L. Paganini, M. J. Mumma, B. P. Bonev, G. L. Villanueva, M. A. DiSanti, J. V. Keane, K. J. Meech
We present spectral and spatial information for major volatile species in
Comet 10P/Tempel 2, based on high-dispersion infrared spectra acquired on UT
2010 July 26 (heliocentric distance Rh = 1.44 AU) and September 18 (Rh = 1.62
AU), following the comet's perihelion passage on UT 2010 July 04. The total
production rate for water on July 26 was (1.90 \pm 0.12) \times 10^28 molecules
s-1, and abundances of six trace gases (relative to water) were: CH3OH (1.58%
\pm 0.23), C2H6 (0.39% \pm 0.04), NH3 (0.83% \pm 0.20), and HCN (0.13% \pm
0.02). A detailed analysis of intensities for water emission lines provided a
rotational temperature of 35 \pm 3 K. The mean OPR is consistent with nuclear
spin populations in statistical equilibrium (OPR = 3.01 \pm 0.18), and the
(1{\sigma}) lower bound corresponds to a spin temperature > 38 K. Our
measurements were contemporaneous with a jet-like feature observed at optical
wavelengths. The spatial profiles of four primary volatiles display strong
enhancements in the jet direction, which favors release from a localized vent
on the nucleus. The measured IR continuum is much more sharply peaked and is
consistent with a dominant contribution from the nucleus itself. The peak
intensities for H2O, CH3OH, and C2H6 are offset by ~200 km in the jet
direction, suggesting the possible existence of a distributed source, such as
the release of icy grains that subsequently sublimed in the coma. On UT
September 18, no obvious emission lines were present in our spectra,
nevertheless we obtained a 3{\sigma} upper limit Q(H2O) < 2.86 \times 10^27
molecules s-1.
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http://arxiv.org/abs/1201.5166
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