The C2-hydrocarbon link in cometary comae

Comet 8P/Tuttle was the target of an ESO multiwavelength observing
campaign in 2008. Observations of the spatial distribution of C2 and C3
were obtained, as well as simultaneous direct detections of the C2
parent species C2H2 and C2H6. We combine these observations to
investigate the origin of cometary C2. The observed C2 column densities
are inconsistent with a production of C2 from C2H2, C2H6, and C3. Based
on a photochemical model, we quantitatively discuss the influence of
further potential C2 parent species. The assumption of C4H2 as an
additional C2 parent species in comet 8P/Tuttle provides the best
explanation for the observed C2 column densities.