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R. R. Howell (U. Wyoming), R. M. Lopes (JPL)
Galileo-NIMS observations of Loki Patera show temperature effects which, although generally consistent with silicate resurfacing wave models, may require additional heat transfer and buffering due to volatiles. For example discrete, different, temperatures are seen at various margins of the patera, and are all considerably lower than those expected for exposed silicate magma. Furthermore, although an assumed resurfacing wave coupled with silicate cooling models can reproduce the general surface temperature trend in the main patera, the temperature values (ignoring a very small ``hot crack" component) are uniform within a couple degrees Kelvin over tens of km. A silicate cooling model has difficulty producing such uniformity in the presence of even minor variations in material properties such as vesicularity or conductivity. We have begun extending the silicate cooling models to include volatiles to determine the magnitude of the effects they cause. For example simple sulfur sublimation driven transfer of latent heat from a ~ 300K typical surface to a nearby cooler one provides insufficient buffering due to the slow sublimation rate at 300K. However temperatures sufficiently high (350K) to drive the required sulfur sublimation are found just 0.3m into a cooling silicate crust. Thus vertical plus horizontal transport of sulfur vapor may provide a viable buffering mechanism.
We have also begun analyzing SSI and Voyager images to obtain ``spectra" of selected spots in the Loki region to search for possible evidence of volatiles. Preliminary analysis indicates that several locations just outside the patera have ``red" spectra indicative of short chain sulfur compounds resulting from sulfur vaporization/deposition. Subtle albedo patterns in the patera itself may provide further evidence of volatiles.
This work is supported by NASA PG&G grant NAG5-11730.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.