The International ISSI Team "Comet 67P/Churyumov-Gerasimenko Surface Composition as a Playground for Radiative Transfer Modeling and Laboratory Measurements"

Abstract

The Rosetta mission provided unprecedented information about 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) nucleus properties and evolution along its orbit around the Sun. The composition of cometary nuclei is considered as representative of the composition of the outer regions of the early solar nebula and is a direct proxy to constrain the physical conditions of the early phases of the Solar System. Remote sensing observations at visible-infrared (VIS-IR) wavelengths of the nucleus of comet 67P/C-G performed by VIRTIS and OSIRIS aboard the Rosetta mission have revealed a surface ubiquitously covered by low-albedo material, characterized by the presence of refractory and semi-volatile organics and dark opaque phases. However, a quantitative determination of the physical properties (grain size, porosity) and chemical composition of the surface regolith, from spectrophotometric analysis, is still missing. The surface composition of 67P/C-G will be investigated within an international team hosted by ISSI (International Space Science Institute, Bern, CH), taking advantage of available and dedicated laboratory reflectance measurements of cometary analogue samples and radiative transfer models. The convergence between models and measurements will allow us to provide a thorough characterization of 67P/C-G surface. At the same time, the comparison of theoretical predictions with results from laboratory reflectance spectroscopy on powders of analogue materials give us the possibility to constrain the capability of the radiative transfer models to characterize sample composition (endmember abundances and mixing modalities) and physical properties.