An enduring mystery regarding the origin of life is how biology could have arisen from non-biological chemical processes. However compounds containing cyanide and carbon monoxide – poisons to deadly to humans – could be key to understanding how creation occurred. The compounds were discovered in carbon-rich asteroids by US space agency NASA and may have helped power life on early Earth.
The extraterrestrial compounds found in asteroid remnants resemble enzymes called hydrogenases, that provide energy to bacteria and archaea by breaking down hydrogen gas.
And NASA’s scientific study suggests these compounds were also present on early Earth, before life began.
This was a period when early Earth was continually bombarded by asteroids and meteorites and the planet’s atmosphere was hydrogen-rich.
Dr Karen Smith, of Boise State University and senior researcher of the NASA study said: ”When most people think of cyanide, they think of spy movies – a guy swallowing a pill, foaming at the mouth and dying, but cyanide was probably an essential compound for building molecules necessary for life”
Cyanide, a carbon atom bound to a nitrogen atom, is surprisingly crucial for the origin of life.
The compound is involved in the non-biological synthesis of organic compounds like amino acids and nucleobases.
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These are the building blocks of proteins and nucleic acids used by all known forms of life.
Dr Smith and her colleague Professor Mike Callahan developed new techniques to extract and measure ancient traces of cyanide in asteroid.
The scientists discovered asteroids containing cyanide belong to a group of carbon-rich space rocks called CM chondrites.
Other types of meteorites tested, including a meteorite from Mars, contained no cyanide.
NASA’s Dr Jason Dworkin added: “Data collected by the NASA OSIRIS-REx spacecraft of asteroid Bennu indicate it is related to CM chondrites.
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“OSIRIS-REx will deliver a sample from Bennu to study on Earth in 2023.
“We will search for these very compounds to try to connect Bennu to known meteorites and to understand the potential delivery of prebiotic compounds such as cyanide, which may have helped start life on the early Earth or other bodies in the solar system.”
Cyanide has been detected in space rocks before.
The new NASA study, however, discovered cyanide and carbon monoxide were attaching with iron to form stable compounds in the asteroids.
The scientists identified two different iron compounds in the asteroids using high-resolution mass spectrometry.
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Professor Callahan said: ”One of the most interesting observations from our study is that these iron cyano-carbonyl complexes resemble portions of the active sites of hydrogenases, which have a very distinct structure.”
The hydrogenase enzymes are present in almost all modern bacteria and archaea and are widely believed to be ancient in origin.
Hydrogenases are large proteins, but the the region where chemical reactions take place happens to be a much smaller metal-organic compound contained within the protein, according to Callahan.
It is this compound that resembles the cyanide-bearing compounds the team discovered in asteroids.
The similarities between the active sites in hydrogenase enzymes and the cyanide compounds the team found in meteorites suggests non-biological processes in the parent asteroids of meteorites and on ancient Earth could have made molecules useful to emerging life.
Dr Smith added: ”Cyanide and carbon monoxide attached to a metal are unusual and rare in enzymes.
“Hydrogenases are the exception. When you compare the structure of these iron cyano-carbonyl complexes in meteorites to these active sites in hydrogenases, it makes you wonder if there was a link between the two.
“It is possible iron cyano-carbonyl complexes may have been a precursor to these active sites and later incorporated into proteins billions of years ago.
“These complexes probably acted as sources of cyanide on early Earth as well.”
