Graphene etching on SiC grains as a path to interstellar polycyclic aromatic hydrocarbons formation

Area of Science:

• Astrochemistry
• Materials Science
• Astrobiology

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are abundant in interstellar space, crucial for understanding life's origins.
• The formation and abundance of PAHs in space remain a significant scientific puzzle.
• Unidentified Infrared (UIR) emission features observed in space may originate from complex organic molecules.

Purpose of the Study:

• To investigate a novel top-down formation route for PAHs in interstellar conditions.
• To explore the role of silicon carbide (SiC) stardust in synthesizing organic molecules.
• To explain the observed abundance of organic species and UIR features in space.

Main Methods:

• Mimicking circumstellar environments using ultra-high vacuum chambers.
• Investigating the SiC surface using in situ advanced characterization techniques.
• Employing first-principles molecular dynamics calculations to model chemical processes.

Main Results:

• Aromatic species, including PAHs, are efficiently formed on graphitized SiC surfaces.
• Formation occurs upon exposure to atomic hydrogen under interstellar medium-analogous pressure and temperature.
• Demonstrated a viable top-down synthesis pathway for large quantities of PAHs.

Conclusions:

• Top-down routes on stardust are crucial for explaining the abundance of organic molecules in space.
• This mechanism provides insights into the origin of Unidentified Infrared emission features.
• Highlights the importance of mineral surfaces in interstellar organic chemistry and prebiotic evolution.