Researchers Find Possible Precursors to Early Life on Earth in Meteorite
11 Dec 2002
(Source: Johnson Space Center)
Catherine E. Watson
Johnson Space Center, Houston, Texas
In a study published today in the "International Journal of Astrobiology," researchers state that a meteorite that fell to Earth over northwestern Canada in January 2000 contains a previously unseen type of primitive organic material that was formed long before our own solar system came into being.
The Tagish Lake meteorite fell to Earth over the Yukon Territory of Canada on Jan. 18, 2000. Parts of the meteorite were collected and kept frozen in an unprecedented level of cleanliness to ensure that it was not contaminated by any terrestrial sources.
Through extensive testing using, in part, electron microscopes, the researchers found numerous hollow, bubble-like hydrocarbon globules in the meteorite. They believe these organic globules, the first found in any natural sample, are very similar to those produced in laboratory simulations designed to recreate the initial conditions present when life first formed in the universe.
"While not of biological origin themselves, these globules would have served very well to protect and nurture primitive organisms on Earth," said Dr. Michael Zolensky, an author of the paper and a researcher in the Office of Astromaterials Research and Exploration Science at NASA's Johnson Space Center in Houston. "They would have been ready-made homes for early life forms."
The type of meteorite in which the globules were found is also so fragile that it generally breaks up into dust during its entry into Earth's atmosphere, scattering its organic contents across a wide swath.
"If, as we suspect, this type of meteorite has been falling onto Earth throughout its entire history, then the Earth was provided with these hydrocarbon globules at the same time life was first forming here," Zolensky said. "We were exceedingly fortunate that this particular meteorite was so large that some pieces survived to be recovered on the ground."
Last year, researchers at NASA's Ames Research Center in Moffett Field, Calif., announced that they had made basically identical hydrocarbon globules in the laboratory from materials present in the early solar system and interstellar space.
"What we have now shown is that that these globules were in fact made naturally in the early solar system, and have been falling to Earth throughout time," Zolensky said.
The researchers believe the Tagish Lake meteorite came from the outer asteroid belt, toward Jupiter, and that similar organic materials may have been falling onto the moons of Jupiter, including Europa.
"It is interesting to speculate about the presence of these organics in the ocean we believe may be present under the ice cap of this moon," Zolensky said.
A team of five researchers collaborated on the two-year study. The team was led by Keiko Nakamura of Kobe University in Japan, who was funded by the Japan Society for the Promotion of Science. Nakamura is now working at JSC under a postdoctoral grant from the U.S. National Research Council. Co-authors of the study include Zolensky, who was funded by the NASA Cosmochemistry Program; Satoshi Tomita and Kazushige Tomeoka, both of Kobe University, who were funded by the Japan Society for the Promotion of Science and the Japanese Ministry of Education, Science, Sports and Culture, respectively; and Satoru Nakashima of the Tokyo Institute of Technology, who was also funded by the Japan Society for the Promotion of Science.