Ion bombardment of materials relevant to Astrobiology

Séminaire IPAG de Giovani Strazzula (University of Catania), jeudi 26 mars 2015 à 11h00, IPAG seminar room

An important chapter of Astrobiology is to investigate the complexity of organic materials present in different space environments and the possibility they can be delivered on the early Earth as well as on other objects in the solar system and beyond, thus contributing to the chemical and biological evolution. Many experiments are conducted in several laboratories in the world, to understand the role of ion bombardment in producing complex chemical species after interaction with simple frozen gases (water, ammonia, methane etc.). The idea is that these experiments mimic what happens in several space environments when cosmic ions (e.g. solar wind ions or cosmic rays) irradiate icy objects such as icy mantles on grains in the interstellar medium and objects in the Solar System (comets, trans neptunian objects, interplanetary dust, etc.). The results of some recent experiments will be here presented. In particular :

1. Experiments conducted at the GANIL laboratories (France) of ion bombardment of frozen (16 K) ammonia–carbon dioxide mixtures (also in ternary mixtures with water), showed, by using FTIR spectroscopy, the formation of new molecules and, in particular, of ammonium carbamate, ammonium formate, CO and OCN- [1].
2. At the Catania (Italy) laboratory we have prepared and characterized (by UV-Vis-IR spectroscopy) a set of organic samples, stable at room temperature and above, that are now part of the experiment “Photochemistry on the Space Station (PSS)”. The samples have been prepared after 200 keV He+ irradiation of icy mixtures, namely N2:CH4:CO deposited at 16 K on MgF2 windows furnished by the European Space Agency. Sample are presently exposed to solar radiation (for about 12-18 months), on the EXPOSE-R facility, outside the International Space Station (ISS). It is thought that they are analogous materials of those formed on comets. These materials, when expelled near the Sun, travel the interplanetary medium where they are exposed to the radiation (cosmic rays, solar ion populations, solar photons), before to be eventually delivered on the surfaces of the Earth and of all the other objects in the solar system. When back on Earth, the analysis of what happened during their exposure to interplanetary space, will allow the analysis of their destruction and the evaluation of their lifetime in the inter¬planetary medium [2].