Astrochemists Model Cosmic Processes: Unraveling the Formation Pathway of Fullerenes from PAHs

A significant breakthrough in astrochemistry has provided a robust explanation for the widespread presence of fullerenes, such as buckminsterfullerene (C60), throughout the interstellar medium. An international research collective, including experts affiliated with the University of Colorado Boulder, carried out pioneering laboratory experiments designed to replicate the chemical reactions occurring in the vacuum of deep space. Their findings, detailed in the *Journal of the American Chemical Society*, propose a compelling mechanism: cosmic radiation acts as the essential catalyst, facilitating the transformation of Polycyclic Aromatic Hydrocarbons (PAHs) into these distinctive spherical carbon molecules.

This molecular conversion is considered a pivotal step in the chemical evolution of the Universe, contributing significantly to the formation of complex organic compounds necessary for the subsequent birth of stars and planetary systems. To accurately mirror the harsh conditions of the cosmos, the researchers subjected two smaller PAH molecules—specifically anthracene and phenanthrene—to intense electron beam bombardment. This simulated radiation triggered a critical sequence of events: the loss of hydrogen atoms followed by a radical structural reorganization. During this process, the carbon atoms began assembling themselves into new configurations, featuring both hexagonal and pentagonal rings.

The laboratory modeling yielded an unexpected and crucial result. The data strongly suggests that molecules incorporating five-sided rings (pentagons) represent the vital “missing link” required to bridge the gap between the flat, planar structure of PAHs and the stable, closed-cage structure of fullerenes. This discovery holds immense importance for astrophysics, as it offers a highly probable and potentially ubiquitous mechanism for the generation of fullerenes across vast stretches of space.

The ability to identify these intricate molecules allows the scientific community to gain a deeper comprehension of the chemical processes underpinning the formation of stellar bodies and entire planetary systems. Fullerenes generated through this newly proposed pathway are within the detection capabilities of modern instrumentation, including the powerful James Webb Space Telescope, which can search for these specific molecular signatures.

Crucially, this research redirects the scientific focus away from previously hypothesized high-energy phenomena, such as supernova explosions, toward a more gradual and pervasive process driven by consistent cosmic radiation exposure. Understanding this specific chemical route not only provides a compelling explanation for the extensive presence of C60 throughout the cosmos but also significantly broadens our perspective on how the fundamental building blocks necessary for the emergence of life in the Universe can arise from relatively simple elemental components.