Science: How life came to earth

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The origin of life on Earth is still a mystery to scientists. New study results now suggest that substances from outer space, which only arrived on Earth after the planet was formed, also played an important role.

There are many theories about the origin of life; one particularly widespread assumption is that the first living beings formed in the primordial soup, which was already full of inorganic and organic molecules billions of years ago.

However, where these molecules actually came from is more controversial. “There are theories that volcanic activity in the water led to the formation of these substances, or that it took several dry and wet phases on Earth to form the molecular compounds necessary for life,” astrophysicist Serge Krasnokutski from Friedrich Schiller University Jena told science.ORF.at.

Cosmic influences
In recent years, however, another theory has become increasingly popular among many researchers: studies have shown that some of the molecules in the primordial soup may also have had a cosmic origin, such as peptides, which are a shorter form of proteins.

These short-chain molecular compounds were extremely important for the emergence of life on Earth, as all living organisms consist of the same chemical building blocks at a molecular level. The peptides are formed from individual amino acids and fulfil different bodily functions, such as transporting substances, accelerating reactions, or forming stabilising scaffolds in the cells.

Search for origins underway
Krasnokutski substantiated the theory of cosmic peptides two years ago in a study in which the researchers demonstrated chemical reactions that could have led to the formation of these vital compounds in space under certain conditions. They were presumably formed in cosmic dust clouds, which were then carried to Earth by meteoroids, asteroids, and comets. Amino acids, nucleobases and various sugars that have been detected in meteoroids in the past also show that the peptides could indeed be extraterrestrial in nature.
To investigate this assumption further, the astrophysicist and a Franco-German research team have now simulated the chemical reactions in the laboratory that could have taken place billions of years ago in space. “This is a continuation of our previous investigations, so to speak, but we have now been able to analyse the chemical reactions much more precisely than before and show that only a few substances are needed for this.”

The results of the experiments, which were carried out in vacuum chambers and other environments and which the research team is currently presenting in the journal “Science Advances”, show that carbon (C), carbon monoxide (CO) and ammonia (NH3) were the main substances required to form the vital molecular compounds. “All of this is sufficiently present in the molecular clouds in space,” says Krasnokutski.

Cold-facilitated connections
The extremely low temperatures in space could also have favoured the formation of the peptides. Water has to be broken down into its individual components during the formation of the molecular compounds, which usually require large amounts of energy. However, the extreme cold in the cosmic dust clouds significantly reduces the energy requirement, presumably making it easier for the short-chain peptides to form.

In addition, other carbon particles adhere to the substances due to the cold temperatures in space, protecting the peptides from UV rays’ influence. “Normally, these compounds are quite fragile and are quickly destroyed by UV photons, so the cold helps to protect them from this,” says Krasnokutski.

So, does life on Earth actually originate from outer space? The astrophysicist believes this is likely, even if further studies are needed to clarify the theory definitively.