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M. W. Buie (Lowell Observatory)
The two occultations observed in 2002 (P126, July 20; P131.1, Aug 21) have provided an extremely valuable probe of current atmospheric conditions. The most common and simplest expectation has been a prediction of decreasing surface temperature in response to Pluto receding from the Sun. These expectations are much too simple. The three-fold pressure increase reported by Elliot et al., at the 2002 DPS Meeting requires a increase of roughly 3\circK in the frost temperature. This temperature increase must be generated by an increase in amount of energy absorbed by the surface that more than offsets the lower available incoming insolation. This energy absorption increase can be caused by an inhomogeneous frost distribution coupled with the changing illumination geometry. The increase can also be caused by changes in the albedo of the frosted terrain. As we are learning, the surface and atmosphere of Pluto comprise a very complicated thermal system that depends on the actual insolation deposition combined with the surface albedo distribution and finally buffered by atmospheric transport.
Photometry collected through the 2000 apparition indicated a fading of the lightcurve which was opposite of what was predicted from static albedo models (Buie, DPS 2000 Meeting). In this presentation, I will review this thermal balance and present data constraints (from new and old data) that will guide our understanding of the seasonal atmospheric evolution on Pluto in the context of the new occultation data. New photometric data through 2002 will be discussed as well as the current collection of spectral monitoring data taken over the past decade.
This research was funded by NASA Planetary Astronomy.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.