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Topic Name: Buckyballs Can Come from Outer Space
Category: Solar cells
Research persons: Robert J. Poreda , Jeffrey L. Bada
Location: University of California, San Diego, La Jolla, CA 92093-0212, United States
Details
Carbon-rich meteorites that crash to Earth carry a wealth of information from
far-flung regions of outer space. Now, it seems that some extraterrestrial
baggage survives the long journey intact. A new study shows that carbon
molecules known as fullerenes can originate outside the solar system and ride in
on meteors.
Fullerenes are hollow, spherical molecules made of pure carbon (SN: 6/27/98,
p. 406). The most famous member of the family is buckminsterfullerene,
consisting of 60 carbon atoms arranged in the pattern of a soccer ball. On
Earth, fullerenes can be made in the lab and have been found in rocks seared by
lightning strikes.
Luann Becker of the University of Hawaii in Honolulu and her group isolated
fullerenes from the Allende and Murchison meteorites. Both are carbonaceous
chondrites, a rare meteorite type that contains much organic material. The
researchers found, trapped inside the fullerenes, noble gases whose isotopic
profile did not match those of gases on Earth.
The researchers also isolated fullerenes from a clay sediment layer deposited
during an asteroid impact 65 million years ago. Some scientists believe that
this collision, marking the so-called Cretaceous-Tertiary (KT) boundary, led to
the demise of the dinosaurs (SN: 3/1/97, p. S20:
http://www.sciencenews.org/sn_arc97/75th/rm_essay.htm). The sediment
fullerenes also contain noble gases with unusual isotope ratios.
This research lends support to the idea that organic molecules from space
could have played a role in starting the chemical processes necessary for the
origin of life (SN: 1/9/99, p. 24:
http://www.sciencenews.org/sn_arc99/1_9_99/Bob1.htm). "It confirms the
possibility of organic compounds surviving the trauma of a large [meteor]
impact," says Jeffrey L. Bada of the University of California, San Diego.
The findings of Becker, Robert J. Poreda of the University of Rochester
(N.Y.), and Ted E. Bunch of NASA Ames Research Center in Moffett Field, Calif.,
appear in the March 28 Proceedings of the National Academy of Sciences.
In 1996, Becker's group discovered fullerenes in rocks from the Sudbury
Impact Crater in Ontario. This crater was made by an asteroid that hit Earth
1.85 billion years ago. These fullerene molecules contained helium with isotope
ratios that are "truly out of this world, almost out of the solar system," says
Bada.
The 1996 work "came under thorough examination and scrutiny," says Becker,
because the fullerenes in the crater may have arrived intact from elsewhere in
the universe or formed on Earth, perhaps during the asteroid's fiery impact.
Last year, Becker and her colleagues for the first time found fullerenes
within a meteorite.
More recently, the researchers ground up several grams of samples from two
meteorites and the KT boundary sediment. They extracted fullerenes and heated
them under vacuum to make "the gas [inside] pop out," says Becker.
The ratio of two helium isotopes, helium-3 and helium-4, was higher in these
fullerenes than in air. Most dramatic, in the Allende meteorite fullerenes, the
ratio was several thousand times greater than in the atmosphere.
The high ratio confirms the fullerenes' extraterrestrial origins. "If you get
the unusual helium ratios, there's no other way to explain it," says Bada.
"The helium got trapped at the time when the fullerenes formed and remained
there for billions of years," Becker explains. "These trapped gases can tell us
about the early history of the universe."
The researchers extracted mostly carbon-60 and carbon-70, but the meteorites
also contain an abundance of larger fullerenes, Becker notes. More difficult to
extract, they may contain most of the trapped gases.
The results "strongly suggest that the fullerenes are extraterrestrial," says
Dieter Heymann, emeritus professor at Rice University in Houston, who recently
heard Becker lecture. However, it's unclear when they formed, he adds.
References:
Becker, L., R.J. Poreda, and T.E. Bunch. 2000. Fullerenes:
An extraterrestrial carbon carrier phase for noble gases. Proceedings of the
National Academy of Sciences 97(March 28):2979-2983. Abstract available at
http://www.pnas.org/cgi/content/abstract/97/7/2979.
Further Readings:
Cowen, R. 1997. C'est la vie. Science News
152(Nov. 1):284-285.
Monastersky, R. 1998. Chunk of death-dealing asteroid found. Science News
154(Nov. 21):324. Available at http://www.sciencenews.org/sn_arc98/11_21_98/Fob1.htm.
______. 1997. The call of catastrophes. Science News 151(March 1):S20. Available
at http://www.sciencenews.org/sn_arc97/75th/rm_essay.htm.
Pennisi, E. 1992. Fullerenes found in old rock, space. Science News 142(July
11):20.
Peterson, I. 1997. Left-handed excess in meteorite molecules. Science News
151(Feb. 22):118.
Simpson, S. 1999. Life's first scalding steps. Science News 155(Jan. 9):24.
Available at http://www.sciencenews.org/sn_arc99/1_9_99/Bob1.htm.
Wu, C. 1998. Playing ball with new carbon molecules. Science News 153(June
27):406.
About Researcher:
Jeffrey L. Bada
NASA Specialized Center of Research and Training in Exobiology
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, CA 92093-0212
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