UH scientist shows fullerene can be cosmic carbon carriers
A University of Hawai'i geochemist and her colleagues have found extraterrestrial noble gasses encapsulated within "buckyballs" and other fullerene carbon molecules. The discovery provides a new tool for tracing extraterrestrial events in Earth's geological and biological record. It also lends support to the theory that, throughout time, atmospheric gasses and organic compounds were delivered to the surface of planets via asteroid and comet strikes, such as the large impact event that wiped out the dinosaurs 65 million years ago.
"This finding opens new possibilities in looking at the problem of how planetary atmospheres evolved and maybe even how life evolved on Earth and perhaps other moons and planets" says Luann Becker, a researcher in the Hawai'i Institute of Geophysics and Planetology in the University of Hawai'i at Manoa's School of Ocean and Earth Science and Technology, and first author on the paper.
Discovery of these trapped gasses in fullerenes was made by Becker and Robert Poreda, of the University of Rochester's Department of Earth and Environmental Sciences, with Theodore Bunch of NASA Ames Research Center's Astrobiology and Space Research Division. Their findings will appear in the March 28 issue of the Proceedings of the National Academy of Sciences. An advance copy of the article is available online at www.pnas.org after 5 p.m. EST March 20.
Says Poreda: "We have been working on this for five years. By answering questions that were raised in response to our earlier findings, this paper clearly confirms what we said in 1995" about fullerenes as potential delivery systems for extraterrestrial gasses.
Work published by Becker and Bunch in Nature last July, first identified naturally occurring fullerenes in a meteorite. Fullerenes are molecules of 60 or more carbon atoms formed into a hollow cage-like structure. They are named for Buckminster Fuller because the 60-atom C60 structures called "buckyballs" resemble the designer's geodesic dome. The scientists had found significant quantities of very large fullerene molecules, containing as many as 400 carbon atoms, in samples from the 4.6-billion-year-old Allende meteorite that landed in Mexico three decades ago.
The subsequent work examined several Cretaceous/Tertiary boundary (KTB) sediments distributed worldwide, including deposits in Denmark, New Zealand and North America. In each case, fullerenes encapsulated noble gasses with unmistakably extraterrestrial and possibly extra-solar signatures. "Helium from different sources on Earth, like our atmosphere or the emissions from volcanoes, have a very different signature from the helium in a meteorite," Becker explains. "The helium we found within the fullerene cages of Australia's Murchison meteorite, for example, is similar to the helium that existed when our solar system first formed." That finding points to a cosmic source for the fullerenes, since molecules formed in the pressure of an earthly impact event or the heat of wildfires that followed would have encapsulated terrestrial helium.
The scientists looked at the KTB because it is a well-studied sediment layer already shown to contain extraterrestrial iridium, which is a platinum group element, and highly shocked minerals. This sediment layer marks a period of abrupt change in Earth's biology and geology, characterized by mass extinction of the dinosaurs, now generally attributed to the impact of a carbonaceous asteroid that collided with Earth.
Becker hopes to expand the research to other periods of mass extinctionÐsuch as the even more devastating event that delineated the Permian/Triassic boundary 250 million years ago. She hopes to determine if extraterrestrial events trigger global change, including whether fullerenes were the original care packages that delivered volatiles along with the carbon necessary to establish life on Earth.
"We now have a powerful new tracer to look at the sediment layer very carefully," she says. Becker also hopes to work with astronomers to study the formation of fullerenes. "We have yet to learn why these things are there and what they tell us about carbon forming in the universe. We need to figure out how to establish their existence and how to search for it."
The research was supported by grants from the NASA Cosmochemistry and Exobiology Program.
CONTACTS: Luann Becker, University of HawaiŒi, 808 956-5010, lbecker@soest.hawaii.edu Robert Poreda, University of Rochester, 716 275-0051 Theodore Bunch, NASA Ames Research Center Space Science Division, 520 717-1916
NOTE: Lead author Luann Becker will be available in Houston Friday/Saturday March 17-18, for telephone interviews. To make arrangements, contact Cheryl Ernst, 808 956-5941, ernst@hawaii.edu. Dr. Becker will return to HawaiŒi March 20.
Journal
Proceedings of the National Academy of Sciences