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Helium and Neon in CometsTwo comets were observed with EUVE in late 1994. Both comet Mueller and comet Borrelly are short-period comets having well established orbital elements and accurate ephemerides. Spectra of 40 ksec were taken of each. No evidence for emission lines from either Helium or Neon was detected. We calculated limits on the production rates of these atoms (relative to solar) assuming a standard isotropic outflow model, with a gas streaming speed of 1 km/s. The 3-sigma (99.7% confidence) limits (1/100,000 for He, 0.8 for Ne) are based on a conservative estimate of the noise in the EUVE spectra. They are also weakly dependent on the precise pointing and tracking of the EUVE field of view relative to the comet during the integrations. These limits are consistent with ice formation temperatures T greater than or equal to 30 K, as judged from the gas trapping experiments of Bar-Nun. For comparison, the solar abundances of these elements are He/O = 110, Ne/O = 1/16. Neither limit was as constraining as we had initially hoped, mainly because comets Mueller and Borrelly were intrinsically less active than anticipated.
Document ID
19980185830
Acquisition Source
Goddard Space Flight Center
Document Type
Contractor Report (CR)
Authors
Jewitt, David (Hawaii Univ. Honolulu, HI United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1996
Subject Category
Astrophysics
Report/Patent Number
NASA/CR-96-207478
NAS 1.26:207478
Funding Number(s)
CONTRACT_GRANT: NAG5-2631
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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