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The molecular composition of Comet C/2007 W1 (Boattini): Evidence of a peculiar outgassing and a rich chemistry

Villanueva, G. L. and Mumma, M. J. and DiSanti, M. A. and Bonev, B. P. and Gibb, E. L. and Magee-Sauer, K. and Blake, G. A. and Salyk, C. (2011) The molecular composition of Comet C/2007 W1 (Boattini): Evidence of a peculiar outgassing and a rich chemistry. Icarus, 216 (1). pp. 227-240. ISSN 0019-1035.

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We measured the chemical composition of Comet C/2007 W1 (Boattini) using the long-slit echelle grating spectrograph at Keck-2 (NIRSPEC) on 2008 July 9 and 10. We sampled 11 volatile species (H_2O, OH^∗, C_2H_6, CH_3OH, H_2CO, CH_4, HCN, C_2H_2, NH_3, NH_2, and CO), and retrieved three important cosmogonic indicators: the ortho-para ratios of H2O and CH4, and an upper-limit for the D/H ratio in water. The abundance ratios of almost all trace volatiles (relative to water) are among the highest ever observed in a comet. The comet also revealed a complex outgassing pattern, with some volatiles (the polar species H_2O and CH_3OH) presenting very asymmetric spatial profiles (extended in the anti-sunward hemisphere), while others (e.g., C_2H_6 and HCN) showed particularly symmetric profiles. We present emission profiles measured along the Sun–comet line for all observed volatiles, and discuss different production scenarios needed to explain them. We interpret the emission profiles in terms of release from two distinct moieties of ice, the first being clumps of mixed ice and dust released from the nucleus into the sunward hemisphere. The second moiety considered is very small grains of nearly pure polar ice (water and methanol, without dark material or apolar volatiles). Such grains would sublimate only very slowly, and could be swept into the anti-sunward hemisphere by radiation pressure and solar-actuated non-gravitational jet forces, thus providing an extended source in the anti-sunward hemisphere.

Item Type:Article
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URLURL TypeDescription
Blake, G. A.0000-0003-0787-1610
Salyk, C.0000-0003-3682-6632
Additional Information:© 2011 Elsevier Inc. Received 18 May 2011. Revised 27 August 2011. Accepted 30 August 2011. Available online 8 September 2011. G.L.V., M.J.M., M.A.D. and B.P.B. acknowledge support from NASA’s Astrobiology Institute (RTOP 344-53-51), and NASA’s Planetary Atmospheres and Astronomy Programs (RTOPs 344-32-07, 08-PAST08-0034, 08-PATM08-0031). B.P.B. and E.L.G. acknowledge support from the NSF Astronomy and Astrophysics Research Grants Program (AST-0807939), and KMS from the NSF RUI Program. GAB acknowledges support from the NASA Origins of Solar Systems program. We thank James Lyke and the staff of Keck Observatory for general support. The data presented herein were obtained at the W.M. Keck Observatory operated as a scientific partnership among CalTech, UCLA, and NASA. This Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Funding AgencyGrant Number
NASARTOP 344-53-51
NASARTOP 344-32-07
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Comets, Composition; Infrared observations; Astrobiology; Cosmochemistry
Issue or Number:1
Record Number:CaltechAUTHORS:20111221-134601839
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Official Citation:G.L. Villanueva, M.J. Mumma, M.A. DiSanti, B.P. Bonev, E.L. Gibb, K. Magee-Sauer, G.A. Blake, C. Salyk, The molecular composition of Comet C/2007 W1 (Boattini): Evidence of a peculiar outgassing and a rich chemistry, Icarus, Volume 216, Issue 1, November 2011, Pages 227-240, ISSN 0019-1035, 10.1016/j.icarus.2011.08.024. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28554
Deposited By: Ruth Sustaita
Deposited On:21 Dec 2011 22:19
Last Modified:09 Dec 2019 21:58

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