Speaker: Dario Campisi

Title: Towards Interstellar RNA Formation: The Role of Polycyclic Aromatic Hydrocarbons 

Abstract:

Polycyclic aromatic hydrocarbons (PAHs) are important interstellar molecules, locking up about 20% of carbon in space. Their structural similarity to nucleobases inspired the ‘PAH world’ hypothesis, proposing
PAHs as templates for RNA/DNA formation. PAHs in the interstellar medium (ISM) are part of carbonaceous dust, adsorbed on silicate dust, e.g., forsterite (Mg₂SiO₄), or gas-phase molecules. Dust catalyzes PAH adsorption and activates them toward attack by radical atoms, potentially leading to nucleobase formation. Indene, a recently detected PAH, resembles adenine, a nucleobase, suggesting a possible templating role.
In this Aarhus Advanced Studies (AIAS) project, I will study indene and other PAHs’ reactions with N and NH₂ radicals on non-stoichiometric forsterite-ice surfaces under cold ISM conditions, using machine-learning models trained on density functional theory (DFT), with results validated by scanning tunneling microscopy (STM) and temperature-programmed desorption (TPD) experiments. We expect that forsterite will catalyze the addition of N and NH₂ to aromatic rings, which are activated by the dust surface, thereby promoting adenine formation under the low-temperature conditions of star-forming regions. This AIAS-funded project will clarify the PAH-world hypothesis, identify the ISM conditions that promote nucleobase formation, and potentially support observational data from JWST and OSIRIS-REx missions.