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K. H. Baines, R. W. Carlson (JPL/CalTech), E. C. Newman (Edinburgh Univ., U. K.)
Multi-spectral imagery of Jupiter's Great Red Spot (GRS) acquired by the Galileo/NIMS are used to constrain the temporal and spatial variability of the vertical aerosol structure and the distribution of ammonia in and around this most-prominent anti-cyclonic feature. As previously noted (Baines et al., B. A. A. S. 28, 1136, 1996), the GRS exhibits a high-altitude core spanning about 3/4 of its visual size when viewed with moderate absorption wavelengths, indicating a bulk elliptical, "wedding cake" shape in it's overall three-dimensional cloud structure. A distinctive spiral pattern within the GRS core is seen in moderate methane and hydrogen absorption bandpasses. This pattern - which has been modelled to show a 2 km variation in cloudtop pressure within the GRS - is inconsistent with a different spiral-shaped pattern observed in ammonia-sensitive wavelengths, thus indicating spatial variability not only in the column abundance of ammonia within the GRS, but in its mixing ratio as well.
An anomolous feature is observed to the northwest of the GRS in images obtained June 27, 1996. Located in the turbulent region to the northwest of the GRS, at 329.2 W, 11.8 S (System III, planetocentric), the feature exhibits (1) high reflectivity at continuum and moderate absorption wavelengths below 2.0 micron, (2) low thermal transmission at 5 micron, but (3) anomolously low reflectivity at the 2.73-micron continuum. Together, these measurements suggest an optically thick, far-red-absorbing cloud at moderately-high altitudes (above 1 bar), perhaps indicative of unusually vigorous vertical transport of large (several micron diameter) ammonia or water particles to the high troposphere induced by the turbulent flow associated with the GRS. If so, this turbulent region may be the best site yet found for mining the deep clouds of Jupiter.
The author(s) of this abstract have provided an email address for comments about the abstract: kbaines@aloha.jpl.nasa.gov