NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
En Route to Destruction: the Evolution in Composition of Ices in Comet D 2012 S1 (ISON) Between 1.2 and 0.34 Au from the Sun as Revealed at Infrared WavelengthsWe report production rates for H2O and eight trace molecules (CO, C2H6, CH4, CH3OH, NH3, H2CO, HCN, C2H2) in the dynamically new, Sun-grazing Comet C2012 S1 (ISON), using high-resolution spectroscopy at Keck II and the NASA IRTF on 10pre-perihelion dates encompassing heliocentric distances Rh1.210.34 AU. Measured water production rates spanned two orders of magnitude, consistent with a long-term heliocentric power law Q(H2O) Rh-3.10.1). Abundance ratios for CO, C2H6, and CH4 with respect to H2O remained constant with Rh and below their corresponding mean values measured among a dominant sample of Oort Cloud comets. CH3OH was also depleted for Rh 0.5 AU, but was closer to its mean value for Rh0.5 AU. The remaining four molecules exhibited higher abundance ratios within 0.5 AU: for Rh 0.8 AU, NH3 and C2H2 were consistent with their mean values while H2CO and HCN were depleted. For Rh 0.5 AU, all four were enriched, with NH3, H2CO, and HCN increasing most. Spatial profiles of gas emission in ISON consistently peaked sunward of the dust continuum, which was asymmetric antisunward and remained singly peaked for all observations. NH3 within 0.5 AU showed a broad spatial distribution, possibly indicating its release in the coma provided that optical depth effects were unimportant. The column abundance ratio NH2H2O at 0.83 AU was close to the typical NHOH from optical wavelengths, but was higher within 0.5 AU. Establishing its production rate and testing its parentage (e.g., NH3) require modeling of coma outflow.
Document ID
20170002498
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Disanti, M. A.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Bonev, B. P.
(Catholic Univ. of America Washington, DC, United States)
Gibb, L. E.
(LENTECH, Inc. Greenbelt, MD, United States)
Paganini, L.
(Catholic Univ. of America Washington, DC, United States)
Villanueva, G.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Mumma, M. J.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Keane, J. V.
(Hawaii Univ. Honolulu, HI, United States)
Blake, G. A.
(California Inst. of Tech. Pasadena, CA, United States)
Dello Russo, N.
(Johns Hopkins Univ. Laurel, MD, United States)
Meech, K. J.
(Hawaii Univ. Honolulu, HI, United States)
Vervack, R. J., Jr.
(Johns Hopkins Univ. Laurel, MD, United States)
McKay, A. J.
(Texas Univ. Austin, TX, United States)
Date Acquired
March 23, 2017
Publication Date
March 16, 2016
Publication Information
Publication: The Astrophysical Journal
Publisher: IOP Publishing
Volume: 820
Issue: 1
ISSN: 2041-8205
e-ISSN: 2041-8213
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN40189
Funding Number(s)
CONTRACT_GRANT: NNG12CR32C
CONTRACT_GRANT: NNX13AD84A
CONTRACT_GRANT: NNH14CK55B
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available