A Meteor’s Protective Bubbles?
A Meteor’s Protective Bubbles?
|Tagish Lake meteor fragments preserved in sample bag|
In a study published 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.
|Time series of fireball trail
Credit: Aflin photo
"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. The delicate charcoal found on Tagish Lake indeed is a rare example of a meteor class called carbonaceous chondrites: meteorites which make up about three per cent of the space rocks recovered. The possible chemical class of this fall constitutes less than 0.1 per cent of all meteorites recovered to date, and represents the most primordial samples known from the early solar system. The largest piece recovered weighed about a half a pound (200 grams) and a total of 2 pounds have been recovered (~1 kg).
"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."
"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.
|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
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. "Scientists believe the molecules needed to make a cell’s membrane, and thus for the origin of life, are all over space. That discovery implied that life could be everywhere in the universe," said Dr. Louis Allamandola, the NASA Ames team’s leader.
Using simple, everyday chemicals, researchers from Ames’ Astrochemistry Laboratory and the Department of Chemistry and Biochemistry at the University of California, Santa Cruz, had created, for the first time, "proto"-cells. These are the primitive cells that mimic the membranous structures found in all life forms. "This process happens all the time in the dense molecular clouds of space," Allamandola said.
"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.
Jupiter’s moon Europa is thought to be one of the most likely abodes for microscopic life in our solar system. The ice-covered world may have liquid water, energy, and organic compounds – all three of the ingredients necessary for life to survive.
Streaks of reddish-brown color highlight cracks in Europa’s outer layer of ice. Some scientists have speculated that microorganisms suspended in Europa’s ice may be the cause of these colorations.
Europa’s average surface temperature is minus 162 C (minus 260 F), and it has an almost non-existent atmospheric pressure of 10-7 of a bar. (In comparison, the average atmospheric pressure at the surface of the Earth is approximately 1 bar.) NASA hopes to launch a Europa Orbiter mission in 2008, with the primary goal of determining if there indeed is a global, subsurface ocean.
While the Tagish Lake samples can be compared to sampling the early solar system or a comet, there are forthcoming attempts to get an even closer look.
Notably in the next few months, on April 23-24, 2003, a real cometary dust stream is expected to contribute several percent to the Earth’s stratospheric flux, and a recent proposal by scientists at University of Washington, St. Louis, has suggested sampling this debris.
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.
Related Web Pages
International Meteorite Organization — more than 1,500,000 meteors obtained by standardized observing methods which were collected during the last 15 years.
Fireball Video–Example (April 10,2000) of meteor breakup (AVI movie)
Carbonaceous Clues to the Early Solar System
Ice on Europa
Interpreting Europa’s Features
Infrared Spectroscopy: An Overview
Galileo Project Home
Protection of Bacterial Spores in Space, a Contribution to the Discussion on Panspermia Horneck, et. al, Origins of Life and Evolution of the Biosphere 31: 527-547, 2001.