The trials and tribulations of PAHs in asteroids: investigating aqueous alteration of polycyclic aromatic hydrocarbons under asteroidal conditions

Carbonaceous asteroids preserve a record of early solar system processes, where minerals and organic molecules, like polycyclic aromatic hydrocarbons (PAHs), offer clues to planetary evolution and prebiotic chemistry. This thesis explores whether aqueous alteration, liquid water interacting with rock, affects the behaviour of PAHs in asteroids. We examined how PAHs respond to water, mineral surfaces, and internal heat within asteroids through experiments and modelling. Results show that PAHs are chemically stable under asteroidal conditions but can be physically mobilized by water flow, especially where the solubility of PAHs increases with temperature. Smaller PAHs may form carbon-rich globules, as seen in meteorites, while larger PAHs like coronene remain unchanged. PAHs are not promising precursors for amino acids under the investigated conditions. However, other asteroidal conditions may favour reactions and remain unexplored. Ultimately, hydrothermal convection can redistribute stable PAHs and possibly other organics, making temperature a key factor in shaping their fate and distribution in asteroidal parent bodies. These findings clarify the role of water in shaping the distribution, stability, and chemical potential of PAHs in asteroids.<br>