University of Hawai'i at Manoa organic geochemist Luann Becker and NASA colleagues Theodore E. Bunch and Louis J. Allamandola discovered the presence of fullerene carbon molecules in the 4.6-billion-year-old Allende meteorite, which has been of interest to scientists since it landed in Mexico three decades ago.
The scientists' report will appear in the July 15 issue of the British journal Nature. Becker shared their findings with fellow scientists during the triennial meeting of the International Society on the Origins of Life this week in San Diego, Calif.
"It's not every day that you discover a new carbon molecule in nature; that's what makes this interesting," Becker says. "If it played a role in how the earth evolved, that would be important."
Fullerenes are soccer-ball shaped molecules (hence their name, which honors geodesic-dome designer Buckminster Fuller) of 60 or more carbon atoms. Their discovery in 1985 as only the third form of pure carbon (along with diamonds and graphite) earned U.S. scientists Robert F. Curl Jr. and Richard E. Smalley and British researcher Harold Kroto the 1996 Nobel Prize in Chemistry. The trio accidentally synthesized these three-dimensional forms of carbon molecules in the laboratory while trying to simulate the high-temperature, high-pressure conditions in which stars form.
Scientists hypothesized that fullerenes also exist naturally in the universe. Becker, who earlier discovered the presence of fullerenes in deposits at the site of the Sudbury impact crater in Ontario, Canada, and her colleagues were able to document naturally occurring fullerenes by exploiting a unique property characteristic of organic molecules. Unlike their pure-carbon cousins, which maintain a solid state, fullerenes can be extracted in an organic solvent.
Becker crushed a piece of the Allende meteorite, demineralized the sample with acids, and used the organic solvent to extract fullerenes from the residue. The scientists found not only the C60 and C70 molecules believed to be most prevalent, but also significant quantities of C100 to C400 molecules. This is the first discovery of higher fullerenes in a natural sample.
Because the multiple atoms in the molecule form a hollow, closed cage that can trap gasses inside, they may have delivered from their stellar birthplace both the carbon that is an essential element to life and the volatiles that contributed to the planetary atmospheres needed for the origin of life. At the very least, the molecules and their contents will tell scientists more about the early solar nebula or presolar dust existing when meteorites like Allende were formed.
Carbon and Life at SpaceDaily