Organic components of cometary nuclei and the effects of opaque phases on spectral detectability of cometary organics and minerals.

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The research proposal is aimed at (1) development of a careful approach to spectroscopic identification and characterization of organics on the surfaces of comet nuclei by taking into account influence of opaque phases (in particular, Fe-sulfides), as well as possible optical alteration caused by irradiation of the surfaces with charged particles and thermal processing of organics at perihelion; (2) spectroscopic characterization of organic components exposed on the nucleus of comet 67P/Churyumov-Gerasimenko. These goals will be achieved through several different approaches, including laboratory experiments, theoretical calculations, and interpretation of new VIS-IR reflectance spectra of comet 67/P. The proposed work will include (1) spectral reflectance studies (0.4-20 micrometers) of analogue materials for cometary refractory organics, carefully selected based on the previous work and the most up-to-date information provided by the ESA's Rosetta mission; (2) spectral reflectance studies of unheated and heated intimate mixtures of Fe-sulfides with selected organics and minerals relevant to comets; (3) application of radiative transfer models to simulate reflectance spectra of organic-sulfide intimate mixtures and space weathering effects; (4) analysis/interpretation of the VIRTIS/Rosetta spectra of comet 67/P in terms of detectability and relative abundances of organic and inorganic surface constituents.; (5) comparative analysis of spectral variability among comet nuclei, dark TNOs, low albedo asteroids and carbonaceous meteorites based on the obtained results. The expected results can significantly contribute to our understanding the spectral variability among dark small bodies of the solar system, and provide new insights into the nature and distribution of organic materials throughout the outer solar system.