Ultraviolet photoprocessing of interstellar dust mantles as a source of polycyclic aromatic hydrocarbons and other conjugated molecules

By co-depositing a gas mixture of simple carbon- and nitrogen-containing mo lecules with water on a 10 K surface and exposing it to ultraviolet radiati on, we were able to form a residue. This residue was then placed aboard the EURECA satellite behind a magnesium fluoride window and exposed to solar r adiation for 4 months before it was returned and analyzed. The resulting re sidue is believed to simulate the photoprocessing of organic dust mantles i n the interstellar medium. Mass spectrometry indicated that the photoproces sing created a rich mixture of polycyclic aromatic hydrocarbons (PAHs) and other conjugated organic molecules, which may explain how PAHs are replenis hed in space.