Thermal Properties of the Surface of 67P/Chryumov-Gerasimenko: Initial Results

Abstract

The imaging spectrometer VIRTIS onboard Rosetta (Coradini et al., 2007) acquires spectra in the range from the near-UV through the IR (0.25-5 micron). Infrared spectra are affected by thermal emission from the surface of the comet, so the measured radiance in that spectral region can be used to retrieve surface temperatures and spectral emissivities by means of temperature-retrieval algorithms (Tosi et al., 2014, Erard, 2014). The temperature of a surface, and in particular its variation with respect to illumination conditions, depends strongly on the thermal inertia of the materials composing this surface and the sub-surface, but also on the topography and small scale roughness. Theoretical codes computing surface and subsurface temperatures under a range of different assumptions on the composition, activity and physical status of the surface matter are used to reproduce the IR radiances observed, and the apparent/effective thermal inertia determined in this way is assumed to correspond to reality (Capria et al., 2014). The initial results obtained using the data acquired during the approach and pre-landing (July 2014-November 2014) first phases of the Rosetta mission will be presented. Authors acknowledge the funding from Italian, German and French Space Agencies.