[meteorite-list] A Meteor's Protective Bubbles? (Tagish Lake Meteorite)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:23:44 2004
Message-ID: <200303031753.JAA19807_at_zagami.jpl.nasa.gov>

http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=388&mode=thread&order=0&thold=0

A Meteor's Protective Bubbles?
Astrobiology Magazine
March 3, 2003

Summary: To survive its fiery descent through a planet's atmosphere,
hitching a ride inside a protective carbon bubble may have improved the
survival chances of organic life if it came from interplanetary fragments.

A Meteor's Protective Bubbles?

Adapted from NASA Johnson release
(http://www.jsc.nasa.gov/news/releases/2002/J02-122.html)

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.

"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.

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.

What's Next

"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.
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Received on Mon 03 Mar 2003 12:53:16 PM PST