In our Galaxy, 20% of the interstellar mass is found in dense molecular clouds. The collapse of the densest cores leads to the formation of a protostar and a protoplanetary disk that evolve to form a stellar and planetary system. The chemical composition of planets is set by the composition of the protoplanetary disk, that is to some extent inherited from the parental cloud. Therefore, the study of the chemical processes in these clouds is key to understand the origin of the chemical complexity found in protoplanetary disks, and in our own Solar System. Dense clouds have T down to 10K in their interiors, allowing gas molecules to condense onto dust grains and form bi-layered ice mantles. The polar layer is mainly composed by H2O. When the T is lower than ~30K the apolar layer is formed, containing CO and other volatile molecules such as N2 and H2. Most experimental simulations performed under astrophysically relevant conditions have studied the chemistry induced in the polar layer by the energetic processing of these ices, but very little is known about the chemistry of the apolar layer. In this talk I will present the first experiments aiming to explore the processes that take place on a H2:N2:CO ice analog upon irradiation with both electrons and ly-alpha photons. The experiments were performed in the new SPACE TIGER setup at the Center for Astrophysics, that allow us to work with ice analogs at temperatures down to 4 K. These experiments simulate the processing of interstellar ices with secondary electrons (produced by the interaction of cosmic rays with the ice mantles), and the secondary UV field (produced by the interaction of cosmic rays with gaseous H2). While electron irradiation induce the formation of CO2, H2CO, and HNCO (and small amounts of CH4 and H2O not shown in the attached IR spectrum), photon irradiation quench the chemistry of H2 and N2. The formation of HNCO is of particular interest, since it is the simplest molecule containing the peptide bond (N-C=O), the molecular bridge that connects amino acids in proteins, and its interstellar origin is still unclear.

Exploring the chemistry induced on the apolar layer by energetic processing of ices in very cold interstellar environments

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.