Image: Asteroid
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This artist's illustration shows an asteroid impact on Earth. Between 4.2 and 3.8 billion years ago, in a period known as the Late Heavy Bombardment, space rocks rained down on the planet 100,000 times more frequently than they do today. Some of those impacts may have stirred the chemistry in Earth's early oceans that would later give rise to life, say scientists.
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updated 12/8/2008 4:58:21 PM ET 2008-12-08T21:58:21

Better known as end-bringers than life-givers, asteroid impacts may have forged the chemicals essential for life in Earth's ancient oceans.

Between 4.2 and 3.8 billion years ago, in a period known as the Late Heavy Bombardment, space rocks rained down on the planet 100,000 times more frequently than they do today. It would seem an inhospitable environment for life to take its first tentative steps.

But new research on the chemistry of this fiery onslaught suggests the impacts produced a host of carboxylic acids, amines, and amino acids — essential compounds for building proteins, and a food source for primitive organisms.

Yoshihiro Furukawa of Tohoku University in Japan and a team of researchers found how these complex molecules were forged in a laboratory experiment mimicking the impact of an iron and carbon-rich asteroid into seawater.

"Carbon and nitrogen are already abundant in the atmosphere," Takeshi Kakegawa, also of Tohoku University, said. "But hydrogen and oxygen are still needed to form organic molecules."

That's where the asteroid comes in. In an impact, the iron in a meteorite acts as a catalysts to break up water molecules, allowing hydrogen and oxygen to bond with carbon and nitrogen to form the complex molecules.

The group's experiment was small; each sample weighed about one-fourth of a gram, or less than the weight of a small paper clip. But if extrapolated to the huge impacts that were thought to have occurred during the Late Heavy Bombardment, the team estimated that over 100 billion metric tons of organic material could've been produced in this way.

If diluted throughout early Earth's ocean, it probably wouldn't do much to stimulate the emergence of life. Instead, Matthew Pasek of Arizona University argues the molecules must be concentrated in some way if they were to form a stew suitable to give rise to the first living creatures.

"One way to overcome the dilution problem would be with a crater; that would concentrate your reagents. It would make an instant cereal bowl," Pasek said. "You can sort of envision prebiotic experiments going on in hundreds of warm, shallow pools, like Darwin imagined."

The finding also seems to strike a blow against the theory of panspermia — the idea that life or the building blocks of life originated in outer space, and then were transported to Earth by comets and asteroids. The study is published in the current issue of Nature Geoscience.

"Many people think you need to bring amino acids from space," Kakegawa said. "We think that important geological events here on Earth could do this."

© 2012 Discovery Channel

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