Meteorite May Hold Key to Life's Start

Dec. 1, 2006 — Scientists have known for years that meteorites and comets contain organic matter, bolstering theories of a cosmic origin for life. Now, they may have discovered what could be the transport system.

After cutting into and thoroughly analyzing samples from a freshly fallen meteorite, researchers found tiny hollow spheres made of organic material that predates the birth of the solar system.

"It is not a new idea that a lot of organic matter on Earth originally came from meteorites and comets," said Scott Messenger, a NASA scientist at the Johnson Space Center in Houston who studies the isotopic chemistry of extraterrestrial materials.

"What is new here is that we have identified a new physical form of the matter and the source."

Of particular interest to astrobiologists, he added, is the shape of the globules.

"They're not all that different in shape from cells and they're hollow, which is a good structure for protecting the earliest life forms," he said.

One reason why Messenger and his colleagues believe they were able to find the globules is that the meteorite is one of the few that was seen falling to the Earth and recovered in a relatively short time.

Residents of western Canada saw the meteorite arriving as a brilliant fireball in the Yukon sky on the morning of January 18, 2000. Chunks of the meteorite were soon found embedded in the ice of Tagish Lake in Ontario.

The snow- and ice-covered lake essentially froze the meteorite and kept it from becoming contaminated.

"It was a clean place to fall and it was collected very carefully," Messenger said.

The type of meteorite in which the globules were found is fragile and typically breaks up into dust during its entry into Earth's atmosphere.

"If, as we suspect, this type of meteorite has been falling onto Earth throughout its entire history, then the Earth was seeded with these organic globules at the same time life was first forming here," said Mike Zolensky, a NASA cosmic mineralogist and co-author of a paper about the meteorite appearing in this week's issue of Science.

Messenger's wife, Keiko Nakamura-Messenger, the lead author of the study, is credited with finding the globules and bringing them to the attention of her husband and others to chemically analyze.

She sliced an extremely thin sample of the meteorite — so thin it was actually transparent — and looked at it with a specialized electron microscope.

"She noticed these donut-like structures immediately. They're really noticeable and they just jumped right out at her. Once you notice a few, then you look for more and they were everywhere," Messenger said.

The scientists are continuing a difficult chemical analysis of the globules and are looking at other meteorites to see if others contain similar structures.

The globules are impossibly small — on the order of one-trillionth of a gram, says Messenger — so there is not much material to analyze.

The team was able to determine the material was formed in temperatures near absolute zero and deduce that it came from the cold dust cloud from which the solar system was formed.

"These were simple organic compounds free-floating in space and they condensed into something, like forming a raindrop," Messenger said. "It’s astounding to see the globules because we’re seeing how the organic matter formed, possibly in interstellar space. To see that is truly amazing."

Even more provocative is the idea that the material may have been a hull for life to form.

"That doesn't mean these globules have anything to do with being alive," Messenger said, "But forming a structure may be essential for life."