Abstract
Combining stellar occultation observations probing Pluto’s atmosphere from 1988 to 2013, and models of energy balance between Pluto’s surface and atmosphere, we find the preferred models are consistent with Pluto retaining a collisional atmosphere throughout its 248-year orbit. The occultation results show an increasing atmospheric pressure with time in the current epoch, a trend present only in models with a high thermal inertia and a permanent N2 ice cap at Pluto’s north rotational pole.
Highlights
Pluto has an eccentric orbit, e = 0.26, and high obliquity, 102–126° (Dobrovolskis and Harris, 1983), leading to complex changes in surface insolation over a Pluto year, and, in surface temperatures
(1988–2013) have substrate thermal inertias of 1000 or 3162 J mÀ2 sÀ1/2 KÀ1. These values are much larger than the thermal inertia measured from daily variation in temperature on Pluto of 20–30 tiu for the non-N2 ice regions (Lellouch et al, 2011), or on other bodies such as Mimas, 16–66 tiu (Howett et al, 2011)
In 2015, The New Horizons spacecraft will fly past Pluto providing the first close-up investigation of Pluto and its moons (Stern et al, 2008; Young et al, 2008b)
Summary
Pluto has an eccentric orbit, e = 0.26, and high obliquity, 102–126° (Dobrovolskis and Harris, 1983), leading to complex changes in surface insolation over a Pluto year, and, in surface temperatures. When the first volatile ice species, CH4, was discovered on Pluto’s surface, researchers quickly recognized that these insolation and temperature variations would lead to large annual pressure variations, due to the very sensitive dependence of equilibrium vapor–pressure on the surface temperature. Address: 1050 Walnut Street, Boulder, CO 80302, USA
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