Speaker
Description
Carbonate minerals are treated as important tracers of geochemical conditions for a variety of different astronomical objects. Although, the fact that they have been detected in a number of environments where the conditions necessary for hydrothermal formation – universally accepted in the past as the dominant patway – are missing, has fueled interest about their possible alternative formation routes. Today, high-temperature gas-phase reactions and certain radiation induced processes are also thought to be as possible sources of this mineral group.
The radiation chemistry of some carbonate mineral has been studied relatively thoroughly under near-ambient conditions. Interestingly, in contrast, very few experiments have been reported under conditions relevant to astrochemistry. Since carbonate bearing dust particles has been detected even in the vicinity of very young astronomical objects, and it is well known that the radolysis of the carbonate ion could lead to the formation of complex organic molecules – especially in aquous environments – it could be assumed that these processes may contrubute to the chemical evolution of these objects.
In our experiments, we investigated low energy ion bombardemnt induced chemistry radiation chemistry in calcite, a stereotypical carbonate mineral. The experiment were carried out in the AQUILA irradiation apparatus, at HUN-REN Atomki. We bombarded polycrystalline calcite targets developed on zinc selenide substrates with 10 keV H+, D+ and He+ beams, mimicking the effects of solar wind components, at 21 K. We used Fourier Transformed Infrared Spectroscopy to identify the main products in the irradiated layers, and observed the formation of carbon monoxide besides carbon dioxide. The two molecules were formed in comparable quantities, which is interesting, because the formation of CO has never been reported in irradiated calcite samples before. We observed a significant dependance of the formation dynamics of both carbon dioxide and monoxide, on the mass of the projectile ions.
Our results may contribute to a deeper understanding of the potential astrochemical significance of carbonate minerals, particularly with focus on stellar wind dominated astrochemical regions.