NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
The ortho/para ratio of water vapor in Comet HalleyThe ortho/para ratio of H2O is shown to be an invariant in the cometary coma. The dependence of ortho-para ratio on temperature in thermal equilibrium is given, and the nuclear-spin-temperature is defined. Its relation to the physical temperature of the cometary ices is discussed, and the prospects for using the observed ortho/para ratio to infer properties of the cometary nucleus are explored. The ortho/para ratio in Halley's comet is derived from high resolution infrared spectra of near 2.7 microns wavelength. On UT December 24.1, 1985 it was 2.73 + or - 0.17, and on UT March 22.7, 1986 it was 3.23 + or - 0.37. The nuclear-spin-temperature was 35 K (+9 K, -5 K) pre-perihelion, and less than 40 K post-perihelion, at the 67% confidence limit. Both numbers are consistent with modeled values of the equilibrium temperature of the cometary nucleus at aphelion (47 K). However, at the 95% confidence limit they are also fully consistent with temperatures less than 50 K, corresponding to an ortho/para ratio of about 3.0.
Document ID
19870015765
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Mumma, Michael J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Larson, Harold P.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Weaver, Harold A.
(Space Telescope Science Inst. Baltimore, Md., United States)
Date Acquired
September 5, 2013
Publication Date
December 1, 1986
Publication Information
Publication: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas
Subject Category
Astrophysics
Accession Number
87N25198
Distribution Limits
Public
Copyright
Other

Available Downloads

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