Credit: NASA
BRISBANE: Life on Earth may have been kick-started when meteorites crashed into the oceans, generating a soup of organic molecules from inorganic precursors, a new study has found.
The research, reported this week in the journal Nature Geoscience, suggests a new route for how organic molecules like amino acids may have first formed on Earth.
Experts believe a soup of these molecules may have brewed up Earth's earliest life-forms.
Prebiotic molecules
"Our study presents experimental evidences about a new source of prebiotic biomolecules," the study's lead author Yoshihiro Furukawa, of Tohoku University in Sendai, Japan, told Cosmos Online.
There are many ideas about how organic molecules could have been synthesised from inorganic molecules, such as by lightning strikes or in deep sea volcanic vents. However, there is little experimental evidence that any of these methods worked under conditions that were likely to have been present on the early Earth.
To get around that problem, some experts have suggested that organic biomolecules were synthesised elsewhere in the universe and delivered to Earth on meteorites. But Furukawa's team now believe that meteorite impacts could have actually synthesised the molecules themselves.
To make the finding, his team fired meteorite-like balls of iron and carbon into a mixture of water and ammonia, meant to resemble the oceans billions of years ago. In the experiment, the researchers found that the iron and carbon were heated by the impact and reacted with hydrogen and nitrogen to form biomolecules, including fatty acids, amines and the amino acid glycine.
Prebiotic molecules
To make sure that the organic molecules weren't contaminants, the team used a rare isotope of carbon (carbon 13) in their imitation meteorites – and it was this isotope that was found in the resulting soup, proving that it came from the 'meteorite' source.
Meteorite impacts were common on the early Earth, Furukawa said, so it's possible that simple organic molecules concentrated in the oceans and were synthesised into even more complex molecules by subsequent impacts.
However, the researchers are not sure whether the amount of molecules produced could have been enough to have had a role in the genesis of life. "Further experiments are needed for accurate estimations," said Furukawa.
Malcom Walter, an astrobiologist at the University of New South Wales in Sydney, Australia, commented that the study reveals an interesting new mechanism for the formation of biomolecules.
"I've never heard of that particular mechanism before," said Walter. "Combined with other possible mechanisms, it enhances the probability of organic compounds on the ancient Earth and makes it that much more likely that those compounds could assemble into the earliest life forms."
