Fullerenes (C-60 and C-70) in the Sudbury impact structure contain tra
pped helium with a He-3/He-4 ratio of 5.5 x 10(-4) to 5.9 x 10(-4). Th
e He-3/He-4 ratio exceeds the accepted solar wind value by 20 to 30 pe
rcent and is higher by an order of magnitude than the maximum reported
mantle value, Terrestrial nuclear reactions or cosmic-ray bombardment
are not sufficient to generate such a high ratio. The He-3/He-4 ratio
s in the Sudbury fullerenes are similar to those found in meteorites a
nd in some interplanetary dust particles. The implication is that the
helium within the C-60 molecules at Sudbury is of extraterrestrial ori
gin.