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Disappearance of 19P/Borrelly's Silicate Feature in 2001 Apparition Is Attributed to Increase in Grain SizeWe report on observations and analysis of HIFOGS 10 microns spectrophotometry of short period comet 19P/Borrelly on 2003 October 13, 15 UT at the NASA IRTF. 19P/Borrelly is one of two short period comets, comet 4PIFaye being the other, to have a silicate feature detected. During Borrelly s perihelion passage in 1994 December, a silicate feature was present with a flux-to-continuum ratio of 0.25. Two apparitions later in 2003 October, the silicate feature is absent. Thermal emission modeling using amorphous olivine and amorphous carbon shows that a slight increase in grain size accounts for the disappearance of the silicate feature. Analysis of 19P/Borrelly suggests grain size, and not the absence of olivine minerals, may be responsible for the absence of silicate features in most short period comets. 19P/Borrelly is one of the more active short period comets. However, short period comets as a family are less active than long period comets. Short period comets probably originated in the Kuiper Belt and suffered collisions while in residence in the outer solar system. Upon evolution into orbits that take them through the inner solar system, the surfaces of short period comets are exposed to sunlight through their many perihelion passages. This is in contrast to long period comets which probably originated near Jupiter and were expelled to the Oort cloud where they have existed and been exposed to cosmic ray processing. By studying the grain properties in short period comets and comparing to long period comets, we compare the effects on the grain populations of different parent body evolution histories. Upcoming opportunities to study short and long period comets will be advertised.
Document ID
20030069034
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Wooden, D. H.
(NASA Ames Research Center Moffett Field, CA, United States)
Woodward, C. E.
(Minnesota Univ. United States)
Harker, D. E.
(California Univ. San Diego, CA, United States)
Date Acquired
August 21, 2013
Publication Date
June 19, 2002
Subject Category
Astronomy
Meeting Information
Meeting: 35th American Astronomical Society Division of Planetary Sciences Annual Meeting
Location: Monterey, CA
Country: United States
Start Date: September 2, 2003
End Date: September 6, 2003
Funding Number(s)
PROJECT: RTOP 344-37-21-03
Distribution Limits
Public
Copyright
Other

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