Impact event at the Permian-Triassic boundary: Evidence from extraterrestrial noble gases in fullerenes

The Permian-Triassic boundary (PTB) event, which occurred about 251.4 milli on years ago, is marked by the most severe mass extinction in the geologic record. Recent studies of some PTB sites indicate that the extinctions occu rred very abruptly, consistent with a catastrophic, possibly extraterrestri al, cause. Fullerenes (C-60 to C-200) from sediments at the PTB contain tra pped helium and argon with isotope ratios similar to the planetary componen t of carbonaceous chondrites. These data imply that an impact event (astero idal or cometary) accompanied the extinction, as was the case for the Creta ceous-Tertiary extinction event about 65 million years ago.