Cyanide could be a clue to what alien life might look like, study shows

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Cyanide could have helped start life on Earth, scientists have said, in a finding that might give clues about life on other planets.

Far from its reputation as a poisonous and fatal gas, the chemical compound might have helped start the earliest reactions that would bring about life on Earth, according to a new study.

That in turn might help us better understand the chemistry of life on other planets – and how it could be vastly different from what we have previously thought.

“When we look for signs of life—either on the early Earth or on other planets—we base the search on the biochemistry we know exists in life today. The fact that these same metabolic reactions can be driven by cyanide shows that life can be very different,” said Ramanarayanan Krishnamurthy, an associate professor of chemistry at Scripps Research Institute, and lead author on the new research.

Today, there is bacteria on Earth that uses a set of chemical reactions called the reverse tricarboxylic acid cycle, or r-TCA cycle. That turns carbon dioxide and water into the chemical compounds that are central to life.

Scientists think that the r-TCA cycle helped create the molecules necessary for life on the early Earth. But it needs proteins that wouldn’t have existed before life evolved – and while it might have been possible for other metals to have caused those reactions, they would need conditions that are not thought to have been around in the early days of our planet.

Scientists wondered whether another molecule might help. Since cyanide was around on the early Earth, they wondered whether that might be able to produce organic molecules out of carbon dioxide.

When they tried it, it worked. In test tubes, cyanide was able to do the job of proteins or metals.

“It was scary how simple it was,” said Krishnamurthy. “We really didn’t have to do anything special, we mixed together these molecules, waited and the reaction happened spontaneously.”

It is impossible to show for definite what chemistry was around on the early Earth. But the new research offers another possibility – and one that could inform our search for alien life elsewhere.

“It frees us up from saying there must be these metals and these extreme conditions,” says Krishnamurthy. “There could be life that evolves from this cyanide-based chemistry.”