Meteorite's Organic Matter Older Than the Sun, Study Says
Brian Handwerk
http://news.nationalgeographic.com/news/2006/11/061130-meteorite.html

Organic globules found in a meteorite that slammed into Canada's Tagish Lake may be older than our sun, a new study says.

The ancient materials could offer a glimpse into the solar system's planet-building past and may even provide clues to how life on Earth first arose.

"We don't really look at this research as telling us something about [the meteorite itself] as much as telling us something about the origins of the solar system," said Scott Messenger of the NASA Johnson Space Center in Houston, Texas.

Most of the meteorite's material is about the same age as our solar system—about 4.5 billion years—and was likely formed at the same time.

But the microscopic organic globules that make up about one-tenth of one percent of the object appear to be far older.

In a study appearing in tomorrow's issue of the journal Science, Messenger and colleagues report that isotopic anomalies in the globules suggest that they formed in very cold conditions—near absolute zero.

"What's really striking about this is that these globules clearly could not possibly have formed where [the meteorite] itself formed," Messenger said.

"Under those extreme conditions the air that you'd breathe would be solid ice. You would never find those conditions in the asteroid belt or anywhere close to the sun."

Cold Origins

The Tagish Lake meteorite flashed across Earth's northern sky in January 2000.

Most of the object burned up in the atmosphere, but pieces of it crashed in Canada's frozen, sparsely populated Yukon Territory and northern British Columbia.

"It's the lowest density meteorite that's ever been studied," said Peter Brown, a meteor expert and professor at the University of Western Ontario in Canada.

"It's extremely friable"—easily pulverized—"and the material breaks up very easily."

The object's fragile nature is one of the clues that led some scientists to theorize that Tagish Lake could be the most primitive meteorite ever discovered.

"By primitive we don't mean the oldest chronologically," explained Brown, who is not involved with the Science study.

"We mean that the material in the meteorite has been processed the least since it was formed. The material we see today is arguably the most representative of the material that first went into making up the solar system."

The meteorite likely formed in the outer reaches of the asteroid belt, but the organic material it contains probably had a far more distant origin.

The globules could have originated in the Kuiper Belt group of icy planetary remnants orbiting beyond Neptune. Or they could have been created even farther afield.

The globules appear to be similar to the kinds of icy grains found in molecular clouds—the vast, low-density regions where stars collapse and form and new solar systems are born.

Links to Life?

Some scientists speculate that organic matter arriving via ancient meteorites and comets are responsible for the rise of life on Earth.

The unique shape of the newfound globules could be of particular interest to supporters of this theory.

The structures are invisible to the naked eye and resemble minute hollow balls with carbon-rich shells. A chunk of meteorite no larger than a grape could contain a billion of the tiny globules.

Theoretically, their hollow-ball shape could have presented a homey environment of concentrated organic matter where early cellular life could develop.

Such theories boast little evidence but raise many intriguing questions.

"We don't claim that these things are alive or anywhere close to being alive," NASA's Messenger cautioned.

"But the fact is that this material fell down on Earth, and similar if not identical material has been falling onto the Earth for its entire history.

"Understanding the origins of that matter is inherently tied in with understanding the origins of life."