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Comet pegged as driving force behind spawning of life on early Earth

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Scientific community has long been considering the two sides of comet impact – one that takes away lives through mass extinction, the other that spawns life or at least sets into motion a chain of events that bring about life on the planet.

A new study presented at the Goldschmidt geochemistry conference in Prague has looked into the life spawning abilities of comet impact and its authors have claimed that these celestial bodies may indeed have been one of the driving forces that caused substantial synthesis of peptides — the first building blocks of life.

Through a series of experiments mimicking conditions of comet impacts on early Earth, Dr. Haruna Sugahara, from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Yokahama, and Dr. Koichi Mimura, from Nagoya University reveal that conditions at the time of comet impact were ideal for peptide formation that eventually led to synthesis of longer peptides.

For their experiments, the duo used frozen mixtures of amino acid, water ice and silicate (forsterite) at cryogenic condition (77 K), and used a propellant gun to simulate the shock of a comet impact. After analyzing the post-impact mixture with gas chromatography, they found that some of the amino acids had joined into short peptides of up to 3 units long (tripeptides).

They estimated that the amount of peptides produced through such events would be around the same as had been thought to be produced by normal terrestrial processes (such as lighting storms or hydration and dehydration cycles).

According to Haruna Sugahara, “Our experiment showed that the cold conditions of comets at the time of the impacts were key to this synthesis, as the type of peptide formed this way are more likely to evolve to longer peptides.

Sugahara added that their findings could be the key in establishing the role that comet impacts played in delivering the seeds of life to the early Earth.

The duo also believes that this opens up the likelihood that there could have been “similar chemical evolution in other extraterrestrial bodies, starting with cometary-derived peptides.”

Some of the best examples of places where this could have happened are the icy satellites of Jupiter and Saturn, such as Europa and Enceladus. Researchers say that the key step in chemical evolution of complex molecules is the formation of the short peptides and once this process kickstarts, the overall energy requirement is much less than what was initially required.

“Comet impacts are normally associated with mass extinction on Earth, but this works shows that they probably helped kick-start the whole process of life in the first place.”