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Far-Ultraviolet Imaging Spectroscopy of Io's Atmosphere with HST/STIS

1999; American Association for the Advancement of Science; Volume: 283; Issue: 5400 Linguagem: Inglês

10.1126/science.283.5400.353

1095-9203

F. L. Roesler, H. W. Moos, R. J. Oliversen, R. C. Woodward, K. D. Retherford, F. Scherb, M. A. McGrath, W. H. Smyth, P. D. Feldman, D. F. Strobel,

Atmospheric Ozone and Climate

Well-resolved far-ultraviolet spectroscopic images of O i , S i , and previously undetected H i Lyman-α emission from Io were obtained with the Hubble space telescope imaging spectrograph (STIS). Detected O i and S i lines (1250 to 1500 angstroms) have bright equatorial spots (up to 2.5 kilorayleighs) that shift position with jovian magnetic field orientation; limb glow that is brighter on the hemisphere facing the jovian magnetic equator; and faint diffuse emission extending to ∼20 Io radii. All O i and S i features brightened by ∼50 percent in the last two images, concurrently with a ground-based observation of increased iogenic [O i ] 6300-angstrom emission. The H i Lyman-α emission, consisting of a small, ∼2-kilorayleigh patch near each pole, has a different morphology and time variation.