  Buckminsterfullerene (C60) was recently confirmed to be the largest molecule
identified in space. However, it remains unclear how, and where this molecule
is formed. It is generally believed that C60 is formed from the build up of
small carbonaceous compounds, in the hot and dense envelopes of evolved stars.
Analyzing infrared observations, obtained by Spitzer and Herschel, we found
that C60 is efficiently formed in the tenuous and cold environment of an
interstellar cloud illuminated by strong ultraviolet (UV) radiation fields.
This implies that another formation pathway, efficient at low densities, must
exist. Based on recent laboratory and theoretical studies, we argue that
Polycyclic Aromatic Hydrocarbons are converted into graphene, and subsequently
C60, under UV irradiation from massive stars. This shows that alternative -
top-down - routes are key to understanding the organic inventory in space.
