Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 20 June 1986:
Vol. 232. no. 4757, pp. 1523 - 1528
DOI: 10.1126/science.232.4757.1523
Prev | Table of Contents | Next

Articles

Detection of Water Vapor in Halley's Comet

MICHAEL J. MUMMA 1, HAROLD A. WEAVER 2, HAROLD P. LARSON 3, D. SCOTT DAVIS 4, and MICHAEL WILLIAMS 3

1 Head of the Planetary Systems Branch, Code 693, Goddard Space Flight Center, Greenbelt, MD 20771.
2 Associate research scientist at the Center for Astrophysical Sciences, Johns Hopkins University, Baltimore, MD 21218.
3 Members of the Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721.
4 Research Associate at the Steward Observatory, University of Arizona, Tucson, AZ 85721.

Gaseous, neutral H2O was detected in the coma of comet Halley on 22.1 and 24.1 December 1985 Universal Time. Nine spectral lines of thev3 band (2.65 micrometers) were found by means of a Fourier transform spectrometer (lgr/utrilgr sim 105) on the NASA-Kuiper Airborne Observatory. The water production rate was sim6 x 1028 molecules per second on 22.1 December and 1.7 x 1029 molecules per second on 24.1 December UT. The numbers of spectral lines and their intensities are in accord with nonthermal-equilibrium cometary models. Rotational populations are derived from the observed spectral line intensities and excitation conditions are discussed. The ortho-para ratio was found to be 2.66±0.13, corresponding to a nuclear-spin temperature of 32 K (+5 K, -2 K), possibly indicating that the observed water vapor originated from a low-temperature ice.

To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)