DPS 2001 meeting, November 2001
Session 22. Outer Planet Atmospheres II: Chemistry and Thermal Structure
Oral, Chairs: K. Rages, J. Moses, Wednesday, November 28, 2001, 3:00-4:30pm, Regency E

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[22.04] Variability on Uranus and Neptune during HST Cycle 9

K. A. Rages (SPRI/NASA Ames), H. B. Hammel (SSI), G. W. Lockwood (Lowell Observatory), M. Marley (NASA Ames)

Hubble Space Telescope images of Uranus and Neptune obtained during Cycle 9 (July 2000-June 2001) show variability on time scales from days to months. Discrete cloud features are seen on Uranus in most of the 21 images taken at wavelengths longward of 600 nm during seven different visits. Following a previously established pattern, these clouds fall into two distinct groups—small bright spots near the sunrise line in the northern hemisphere and more diffuse patches detached from or condensed within the south polar collar. There is some evidence for a transient 30% decrease in the optical depth of Uranus’ south polar cap during October 2000. On Neptune, the major activity band continued to be ~45\deg S latitude. Areas of more diffuse cloudiness were seen in the north, and a bright plume was visible near 70\deg S in June 2001.

This work was funded through Grant GO-08634, submitted to the Space Science Telescope Institute, which is operated by the Association of Universities for Research in Astronomy.

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