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L.A. Young (SwRI)
Pluto is not a static world, but one where the balance between the atmosphere and surface changes in response to the heiocentric distance and sub-solar latitude. Most models of Pluto's seasonal activity predict the latitudinal migration of tens of cm of frost and changes in the surface pressure of several orders of magnitude [1], and recent stellar occultations show a doubling of Pluto's atmospheric pressure at occultation altitudes [2]. When the New Horizons spacecraft encounters Pluto and Charon, scheduled for 2015, it will give us unprecedented geological maps, surface compositions, and atmospheric profiles [3]. To best interpret the data returned from New Horizons, we need to place Pluto in the context of temporal change over the preceding decade.
Furthermore, the geometry of Pluto's orbit provides new opportunities over the next decade, such as the upcoming ``occultation season" as Pluto crosses the galactic plane, and the chance to measure an opposition surge as Pluto approaches the ecliptic. I will summarize recent improvements in our understanding of Pluto's surface and atmosphere and the planned measurements by New Horizons, and describe how continued observations and models will allow us to understand the seasonal behavior of this rapidly changing world.
\noindent [1] e.g., Hansen & Paige 1996, Icarus 120, 247. [2] Pasachoff et al.\ 2005, AJ 129, 1718; Sicardy et al.\ 2003, Nature 424, 168; Elliot et al.\ 2003, Nature 424, 165. [3] Stern & Spencer\ 2003, Earth Moon and Planets, 92, 477.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.