L.I.F.E. for
Interstellar and circumstellar dust plays a fundamental role in several astrophysical processes and environments, such as in protoplanetary disks, which are structure orbiting pre-main sequence stars for less than ten million years, and which are the site of planet formation. For instance, despite the mass of protoplanetary disks is dominated by gas (mainly hydrogen), their dust grains are mainly responsible for the formation of planetary systems. During few million years, in fact, grains collide and coagulate forming first cm-size aggregates, then km-size rocky planetesimals, and planets. This process is accelerated by the fact that grains are covered by layers of ices, as it has been observed in several spectroscopic studies of disks and clouds (e.g. Whittet et al. 1996).
The interaction between dust grains, ices and stellar radiation has important effects on the chemical evolution of clouds, disks, and newborn planets. The study of this important topic is the main objective the laboratory L.I.F.E. (Light Irradiation Facility for Exochemistry) of the Astronomical Observatory of Palermo. This facility has been designed in order to study the reactions occurring in interstellar ices due to incident of UV and X-ray radiation, which is copiously emitted by pre-main sequence stars.
The study “Chemical Evolution of Interstellar Methanol Ice Analogs upon Ultraviolet Irradiation: The Role of the Substrate” of A. Ciaravella (INAF – Osservatorio Astronomico di Palermo), recently published on The Astrophysical Journal, is the first paper describing experiments performed with L.I.F.E. laboratory. This experiment was designed to study how the chemical reactions induced in ultraviolet-irradiated methanol ices change if they are deposited onto a ZnSe window, inert to UV radiation, or onto a layer of amorphous water-rich magnesium silicate. In order to better reproduce interstellar grains, Si–OH groups and magnesium carbonates are incorporated in the silicate layer. The experiment has shown that the ratio of CO2/CO produced during the irradiation is larger in the ice deposited onto the silicate layer, as a consequence of reactions occurring in the silicate. Thus, this study has shown for the first time that the presence of ice in the dust grains is important for the products of the chemical reactions induced by incident energetic radiation.
The figure (link) shows a scheme of the chamber of L.I.F.E. facility