Organisateur :
Giovanni Strazzulla (INAF-Osservatorio Astrofisico di Catania, Italy);
Antonella Barucci (LESIA)

Solid phase molecules (often referred to as "ices") are present both in the interstellar medium as mantles on interstellar and circumstellar dust and in/on many objects in the Solar System. Ices are exposed to a number of energetic processes such as photolysis by UV photons, and radiolysis by ion and/or electron bombardment.

The interaction between photons and energetic particles with ices produces a number of relevant and potentially observable (some observed) effects. The processing of astrophysical ices starts since their formation as icy mantles on interstellar dust. However in circumstellar environments (including the solar nebula) dust is, to some extent, "reprocessed". The irradiation history, during accretion of planetary objects, may be at least as important as that in the interstellar medium, particularly if accretion occurs in the so called T-Tauri phase during which intense particle fluxes occur. After formation planetary objects are exposed to the fluxes of solar and galactic radiation and energetic particles (e.g. solar wind and cosmic rays).

Laboratory experiments conducted for some decades in some laboratories worldwide have shown that photolysis and radiolysis of ices causes not only the erosion of the target (sputtering or photo-sputtering) but also modification of the structure (crystalline or amorphous) of the sample as well as a number of non-thermal, "hot" chemical reactions that can lead the formation of a large number of molecules and also organic refractory residues. These laboratory experiments simulate relevant targets "irradiated" under physical conditions as close as possible to the astrophysical ones.

While a large amount of experiments have been performed, still this research field needs further efforts. In particular radyolisis and photolysis of icy mixtures resulted in the synthesis of several specific, also complex, molecules. However it is a common feeling that much more molecules are still to be revealed. In fact the detection techniques used up to now, essentially optical spectroscopy (from UV to far IR) and quadrupole mass spectrometry, are sensitive only to the synthesized species whose abundance is larger than several per mill with respect to the original species.

Efforts have to be done to use more sensitive techniques to evidence the formation of additional (complex) molecules and/or fragments that could be of primary relevance for Astrobiology also to understand which species can be searched for, by terrestrial or space facilities, in planetary ices and in the atmospheres of extrasolar planets/moons that testify for the presence of a complex chemistry that could evolve versus a bio-sphere.

The proposed meeting is aimed at contributing to the field by inviting head persons of the most active laboratories in the field to present the "new techniques" that are used or are foreseen to be used in the next years for a more in depth characterization of irradiated ice mixtures. The publication of a paper on a leading journal is foreseen.