Polycyclic aromatic hydrocarbons - from interstellar medium to asteroids and meteorites

Polycyclic aromatic hydrocarbons (PAHs) from the interstellar medium are suggested as precursors to organic molecules found in meteorites and asteroids. Over several projects, we have examined the reactivity of PAHs in aqueous solutions under asteroidal conditions and their feasibility as a precursor to other organic molecules. Here, we want to give a brief insight into the results of our hydrothermal experiments on the example of fluoranthene (C16H10). We performed experiments to test whether aqueous alteration can induce a breakdown or alteration of fluoranthene, potentially leading to the formation of other organic molecules. Additionally, we performed surface analyses on fluoranthene crystals to investigate the liberation of fluoranthene molecules into the fluid phase to examine fluoranthene’s accessibility within different aqueous solutions. Lastly, we integrated our findings into a numerical model to
investigate where in an asteroid such reactions could take place.
Our results show that fluoranthene is very resistant to reaction. If present, newly
formed organic molecules were too low in concentration to be detected using our chosen techniques. We noted the only significant change in fluoranthene was related to its melting point (~110 °C). When fluoranthene in water was heated above its melting point spherules formed morphologically similar to globules detected in meteorites. It, however, still remains unclear whether fluoranthene can react in the fluid phase over the time periods that aqueous alteration may have been active in meteorites and asteroids.