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| Paper: |
Fullerenes, Noble Gases and the Flux of Extraterrestrial Debris to |
| Volume: |
213, Bioastronomy '99: A New Era in Bioastronomy |
| Page: |
243 |
| Authors: |
Becker, Luann; Poreda, Robert; Bunch, Ted |
| Abstract: |
The discovery of fullerenes in deposits associated with two separate impact events involving a large bolide with the Earth suggests that these carbon (C) molecules may also be an indicator of extraterrestrial (ET) events over geologic time. Fullerenes were detected in carbon-rich breccias (Onaping Fm.) associated with the 1.85 byr Sudbury Crater (Becker et al., Science 265, 1994) and in clay sediments within the 65 myr old Cretaceous/Tertiary (K/T) boundary (Heymann et al., Science 265, 1994). To determine the origin of the Sudbury fullerenes, we searched for noble gases trapped inside the fullerene molecules (Saunders et al., Science 259, 1993). The Sudbury fullerenes contain trapped 3He/4He ratios (~5.5 times 10^{-4}) similar to those found in meteorites and some interplanetary dust particles (Becker et al., Science 272, 1996). Preliminary measurements of He in a continental K/T fullerene residue from Raton Basin (Colorado) revealed ^3He/^4He ratios some 100 times above air. A marine K/T residue from Stevns Klint, (Denmark) revealed ^3He/^4He ratios several thousand times above air in the high temperature fraction! We attribute the anomalously high ^3He/^4He ratios and high ^3He concentration in Stevns Klint to the abundance of higher fullerenes in the residue. The high ^3He/^4He ratio in the K/T fullerenes suggests that they were present in the bolide and somehow survived the impact event. Confirmation of these results could have broad implications concerning the importance of exogenous delivery in providing carbon, volatiles and perhaps other organics to the early Earth's crustal reservoir. |
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