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Science 14 November 1980:
Vol. 210. no. 4471, pp. 784 - 786
DOI: 10.1126/science.210.4471.784
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Articles

Io: Longitudinal Distribution of Sulfur Dioxide Frost

Twenty spectra of Io (0.26 to 0.33 micrometer), acquired with the International Ultraviolet Explorer spacecraft, have been studied. There is a strong ultraviolet absorption shortward of 0.33 micrometer that is consistent with earlier ground-based spectrophotometry; its strength is strongly dependent on Io's rotational phase angle at the time of observation. This spectral feature and its variation are interpreted as indicative of a longitudinal variation in the distribution of sulfur dioxide frost on Io. The frost is most abundant at orbital longitudes 72° to 137° and least abundant at longitudes 250° to 323°. Variations in spectral reflectivity between 0.4 and 0.5 micrometer, reported in earlier ground-based spectral studies, correlate inversely with variations in reflectivity between 0.26 and 0.33 micrometer. It is concluded that this is because the Io surface component with the highest visible reflectivity (sulfur dioxide frost) has the lowest ultraviolet reflectivity. At least one other component is present and may be sulfur allotropes or alkali sulfides. This model is consistent with ground-based ultraviolet, visible, and infrared spectrophotometry. Comparison with Voyager color photographs indicates that the sulfur dioxide frost is in greatest concentration in the "white" areas on Io and the other sulfurous components are in greatest concentration in the "red" areas.

Submitted on July 16, 1980


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Hydrogen Sulfide on IO: Evidence from Telescopic and Laboratory Infrared Spectra.
D. B. Nash, D. B. NASH, and R. R. HOWELL (1989)
Science 244, 454-457
   Abstract »    PDF »
Fast Ion Bombardment of Ices and Its Astrophysical Implications.
W. L. Brown, L. J. Lanzerotti, and R. E. Johnson (1982)
Science 218, 525-531
   Abstract »    PDF »


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