| Description |
In 2015, Pluto and its system of satellites will be explored by the New Horizons space mission. Pluto is the most prominent representative of large Kuiper-belt objects with volatile ices (N2, CH4, CO) on their surfaces. Due to its elliptic orbit and strong polar inclination, the large seasonal and spatial variability of the insolation is expected to drive global scale transport of the volatile ices, whose thermal balance determines the atmospheric state.Recent observations of Pluto of various kinds have revealed that it is undergoing seasonal evolution, with changes in its atmosphere, surface spectrum, and thermal emission. In particular, Spitzer observations over 2004-2007 indicated a surprising dimming of the dwarf planet at thermal wavelengths, most probably associated with extension of the coldest, N2-ice dominated, regions. We propose to measure the thermal lightcurve of the Pluto/Charon system (i.e. the rotational variation of its thermal emission) with PACS and SPIRE in order to (i) assess the changes in the ice distribution (ii) determine the emissivities (spectral and bolometric) of Pluto.s different terrains (iii) determine their thermal inertia on seasonal timescales. These parameters are needed to constrain volatile transport and general circulation models, and to put the upcoming New Horizons measurements in a broader, time-evolving, perspective. |
