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Science 28 April 1989:
Vol. 244. no. 4903, pp. 454 - 457
DOI: 10.1126/science.244.4903.454
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Articles

Hydrogen Sulfide on IO: Evidence from Telescopic and Laboratory Infrared Spectra

DOUGLAS B. NASH 1 and ROBERT R. HOWELL 2

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, and San Juan Capistrano Research Institute, San Juan Capistrano, CA 92675.
2 Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071.

Evidence is reported for hydrogen sulfide (H2S) on Io's surface. An infrared band at 3.915 (± 0.015) micrometers in several ground-based spectra of Io can be accounted for by reflectance from H2S frost deposited on or cocondensed with sulfur dioxide (SO2) frost. Temporal variation in the occurrence and intensity of the band suggests that condensed H2S on Io's surface is transient, implying a similar variation of H2S abundance in Io's atmosphere. The band was observed in full-disk measurements of Io at several orbital longitudes, including once at 24°(sim0.5 hour after Io's reappearance after an eclipse)—but not after another reappearance at 22°—and once at 95°(on Io's leading hemisphere). These results suggest that condensed H2S is sparse and variable but can be widespread on Io's surface. When present, it would not only produce the infrared band but would brighten Io's typical surface at ultraviolet and visible wavelengths.

Submitted on November 29, 1988


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Far-Ultraviolet Imaging Spectroscopy of Io's Atmosphere with HST/STIS.
F. L. Roesler, H. W. Moos, R. J. Oliversen, R. C. Woodward Jr., K. D. Retherford, F. Scherb, M. A. McGrath, W. H. Smyth, P. D. Feldman, and D. F. Strobel (1999)
Science 283, 353-357
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Science. ISSN 0036-8075 (print), 1095-9203 (online)