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Title: The Composition of Comet C/2012 K1 (PanSTARRS) and the Distribution of Primary Volatile Abundances Among Comets

Abstract

On 2014 May 22 and 24 we characterized the volatile composition of the dynamically new Oort cloud comet C/2012 K1 (PanSTARRS) using the long-slit, high resolution ( λ /Δ λ  ≈ 25,000) near-infrared echelle spectrograph (NIRSPEC) at the 10 m Keck II telescope on Maunakea, Hawaii. We detected fluorescent emission from six primary volatiles (H{sub 2}O, HCN, CH{sub 4}, C{sub 2}H{sub 6}, CH{sub 3}OH, and CO). Upper limits were derived for C{sub 2}H{sub 2}, NH{sub 3}, and H{sub 2}CO. We report rotational temperatures, production rates, and mixing ratios (relative to water). Compared with median abundance ratios for primary volatiles in other sampled Oort cloud comets, trace gas abundance ratios in C/2012 K1 (PanSTARRS) for CO and HCN are consistent, but CH{sub 3}OH and C{sub 2}H{sub 6} are enriched while H{sub 2}CO, CH{sub 4}, and possibly C{sub 2}H{sub 2} are depleted. When placed in context with comets observed in the near-infrared to date, the data suggest a continuous distribution of abundances of some organic volatiles (HCN, C{sub 2}H{sub 6}, CH{sub 3}OH, CH{sub 4}) among the comet population. The level of “enrichment” or “depletion” in a given comet does not necessarily correlate across all molecules sampled, suggesting that chemical diversity among comets may bemore » more complex than the simple organics-enriched, organics-normal, and organics-depleted framework.« less

Authors:
;  [1]; ; ; ; ;  [2]
  1. Department of Physics and Astronomy, University of Missouri-St. Louis, 503 Benton Hall, One University Blvd., St. Louis, MO 63121 (United States)
  2. Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Mail Stop 690, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22663728
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 153; Journal Issue: 4; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; AMMONIA; CARBON; CARBON MONOXIDE; COMETS; ETHANE; FLUORESCENCE; HYDROCYANIC ACID; METHANE; METHANOL; MIXING RATIO; MOLECULES; PLANETS; RESOLUTION; SATELLITES; TELESCOPES; VOLATILITY; WATER

Citation Formats

Roth, Nathan X., Gibb, Erika L., Bonev, Boncho P., DiSanti, Michael A., Mumma, Michael J., Villanueva, Geronimo L., and Paganini, Lucas, E-mail: nxrq67@mail.umsl.edu. The Composition of Comet C/2012 K1 (PanSTARRS) and the Distribution of Primary Volatile Abundances Among Comets. United States: N. p., 2017. Web. doi:10.3847/1538-3881/AA5D18.
Roth, Nathan X., Gibb, Erika L., Bonev, Boncho P., DiSanti, Michael A., Mumma, Michael J., Villanueva, Geronimo L., & Paganini, Lucas, E-mail: nxrq67@mail.umsl.edu. The Composition of Comet C/2012 K1 (PanSTARRS) and the Distribution of Primary Volatile Abundances Among Comets. United States. doi:10.3847/1538-3881/AA5D18.
Roth, Nathan X., Gibb, Erika L., Bonev, Boncho P., DiSanti, Michael A., Mumma, Michael J., Villanueva, Geronimo L., and Paganini, Lucas, E-mail: nxrq67@mail.umsl.edu. Sat . "The Composition of Comet C/2012 K1 (PanSTARRS) and the Distribution of Primary Volatile Abundances Among Comets". United States. doi:10.3847/1538-3881/AA5D18.
@article{osti_22663728,
title = {The Composition of Comet C/2012 K1 (PanSTARRS) and the Distribution of Primary Volatile Abundances Among Comets},
author = {Roth, Nathan X. and Gibb, Erika L. and Bonev, Boncho P. and DiSanti, Michael A. and Mumma, Michael J. and Villanueva, Geronimo L. and Paganini, Lucas, E-mail: nxrq67@mail.umsl.edu},
abstractNote = {On 2014 May 22 and 24 we characterized the volatile composition of the dynamically new Oort cloud comet C/2012 K1 (PanSTARRS) using the long-slit, high resolution ( λ /Δ λ  ≈ 25,000) near-infrared echelle spectrograph (NIRSPEC) at the 10 m Keck II telescope on Maunakea, Hawaii. We detected fluorescent emission from six primary volatiles (H{sub 2}O, HCN, CH{sub 4}, C{sub 2}H{sub 6}, CH{sub 3}OH, and CO). Upper limits were derived for C{sub 2}H{sub 2}, NH{sub 3}, and H{sub 2}CO. We report rotational temperatures, production rates, and mixing ratios (relative to water). Compared with median abundance ratios for primary volatiles in other sampled Oort cloud comets, trace gas abundance ratios in C/2012 K1 (PanSTARRS) for CO and HCN are consistent, but CH{sub 3}OH and C{sub 2}H{sub 6} are enriched while H{sub 2}CO, CH{sub 4}, and possibly C{sub 2}H{sub 2} are depleted. When placed in context with comets observed in the near-infrared to date, the data suggest a continuous distribution of abundances of some organic volatiles (HCN, C{sub 2}H{sub 6}, CH{sub 3}OH, CH{sub 4}) among the comet population. The level of “enrichment” or “depletion” in a given comet does not necessarily correlate across all molecules sampled, suggesting that chemical diversity among comets may be more complex than the simple organics-enriched, organics-normal, and organics-depleted framework.},
doi = {10.3847/1538-3881/AA5D18},
journal = {Astronomical Journal (Online)},
number = 4,
volume = 153,
place = {United States},
year = {Sat Apr 01 00:00:00 EDT 2017},
month = {Sat Apr 01 00:00:00 EDT 2017}
}
  • Comets C/2011 L4 (PanSTARRS) and C/2012 F6 (Lemmon) were observed throughout their 2012-2013 apparitions with the Solar Wind Anisotropies (SWAN) all-sky hydrogen Lyα camera on board the Solar and Heliosphere Observatory (SOHO) satellite. SOHO has been in a halo orbit around the L1 Earth-Sun Lagrange point since early 1996 and has been observing the interplanetary medium and comets beginning with C/1996 B2 (Hyakutake). The global water production from these comets was determined from an analysis of the SWAN Lyα camera observations. Comet C/2011 L4 (PanSTARRS), which reached its perihelion distance of 0.302 AU on 2013 March 10.17, was observed onmore » 50 days between 2013 January 29 and April 30. Comet C/2012 F6 (Lemmon), which reached its perihelion distance of 0.731 AU on 2013 March 24.51, was observed on 109 days between 2012 November 29 and 2013 June 31. The maximum water production rates were ∼1 × 10{sup 30} molecules s{sup –1} for both comets. The activities of both comets were asymmetric about perihelion. C/2011 L4 (PanSTARRS) was more active before perihelion than after, but C/2012 F6 (Lemmon) was more active after perihelion than before.« less
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  • We report production rates, rotational temperatures, and related parameters for gases in C/2013 R1 (Lovejoy) using the Near InfraRed SPECtrometer at the Keck Observatory, on six UT dates spanning heliocentric distances (R{sub h} ) that decreased from 1.35 AU to 1.16 AU (pre-perihelion). We quantified nine gaseous species (H{sub 2}O, OH*, CO, CH{sub 4}, HCN, C{sub 2}H{sub 6}, CH{sub 3}OH, NH{sub 3}, and NH{sub 2}) and obtained upper limits for two others (C{sub 2}H{sub 2} and H{sub 2}CO). Compared with organics-normal comets, our results reveal highly enriched CO, (at most) slightly enriched CH{sub 3}OH, C{sub 2}H{sub 6}, and HCN, andmore » CH{sub 4} consistent with {sup n}ormal{sup ,} yet depleted, NH{sub 3}, C{sub 2}H{sub 2}, and H{sub 2}CO. Rotational temperatures increased from ∼50 K to ∼70 K with decreasing R{sub h} , following a power law in R{sub h} of –2.0 ± 0.2, while the water production rate increased from 1.0 to 3.9 × 10{sup 28} molecules s{sup –1}, following a power law in R{sub h} of –4.7 ± 0.9. The ortho-para ratio for H{sub 2}O was 3.01 ± 0.49, corresponding to spin temperatures (T {sub spin}) ≥ 29 K (at the 1σ level). The observed spatial profiles for these emissions showed complex structures, possibly tied to nucleus rotation, although the cadence of our observations limits any definitive conclusions. The retrieved CO abundance in Lovejoy is more than twice the median value for comets in our IR survey, suggesting this comet is enriched in CO. We discuss the enriched value for CO in comet C/2013 R1 in terms of the variability of CO among Oort Cloud comets.« less
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