Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published November 2011 | public
Journal Article

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

Abstract

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.

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.

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023