Scientists at Aarhus University have overturned a long-standing assumption about how life’s essential ingredients emerge. New experiments show that the basic components needed to build proteins can form naturally in space, a finding that increases the likelihood that life could exist elsewhere in the universe.

The research was carried out at advanced laboratories at Aarhus University and at a European research facility in Hungary (HUN-REN Atomki). The experiments were led by researchers Sergio Ioppolo and Alfred Thomas Hopkinson.

Recreating the Extreme Conditions of Interstellar Space

Inside a specially designed chamber, the researchers recreated the harsh environment found in vast clouds of cosmic dust located thousands of light-years from Earth. These regions are among the coldest and emptiest places in the universe.

Temperatures in such dust clouds reach about -260°C, and pressure is so low that researchers must constantly remove stray gas particles to maintain an ultra-high vacuum. Under these carefully controlled conditions, the team studied how particles behave when exposed to radiation, closely matching what happens in real interstellar space.

"We already know from earlier experiments that simple amino acids, like glycine, form in interstellar space. But we were interested in discovering if more complex molecules, like peptides, form naturally on the surface of dust grains before those take part in the formation of stars and planets," Sergio Ioppolo says.

From Amino Acids to Protein Precursors

Peptides are short chains made when individual amino acids link together. When many peptides bond, they form proteins, which are essential for life as we know it. Identifying where and how these protein precursors originate is a key step in understanding how life might begin.

To test this process, the researchers placed glycine inside the chamber and exposed it to simulated cosmic rays using an ion accelerator at HUN-REN Atomki. They then analyzed the chemical reactions that followed.

"We saw that the glycine molecules started reacting with each other to form peptides and water. This indicates that the same process occurs in interstellar space," Alfred Thomas Hopkinson says. "This is a step toward proteins being created on dust particles, the same materials that later form rocky planets."

Star-Forming Clouds as Chemical Factories

Ioppolo, Hopkinson, and their colleagues focus on giant dust clouds between stars because these regions are where new solar systems are born. For decades, scientists believed that only very simple molecules could form in these environments.

"We used to think that only very simple molecules could be created in these clouds. The understanding was that more complex molecules formed much later, once the gases had begun coalescing into a disc that eventually becomes a star," Sergio Ioppolo explains.

"But we have shown that this is clearly not the case."

This shift in understanding suggests that key life-related molecules are much more widespread throughout the universe than previously thought.

Implications for Life Beyond Earth

As interstellar dust clouds collapse, they eventually give rise to stars and planets. During this process, tiny chemical building blocks can be delivered to newly formed rocky worlds.

"Eventually, these gas clouds collapse into stars and planets. Bit by bit, these tiny building blocks land on rocky planets within a newly formed solar system. If those planets happen to be in the habitable zone, then there is a real probability that life might emerge," Sergio Ioppolo says.

"That said, we still don’t know exactly how life began. But research like ours shows that many of the complex molecules necessary for life are created naturally in space."

A Chemical Process That Works Everywhere

At first glance, the formation of peptides from simple amino acids might seem like a small step. However, the chemical reaction that links amino acids together follows the same basic rules everywhere, making the discovery especially important.

"All types of amino acids bond into peptides through the same reaction. It is, therefore, very likely that other peptides naturally form in interstellar space as well," says Hopkinson. "We haven’t looked into this yet, but we are likely to do so in the future."

Searching for Other Ingredients of Life

Proteins are only part of the picture. Life also depends on membranes, nucleobases, and nucleotides. Whether these components can also form naturally in space is still an open question.

Researchers at the Center for Interstellar Catalysis, funded by The Danish National Research Foundation, are continuing to investigate these possibilities.

"These molecules are some of the key building blocks of life," explained co-author Professor Liv Hornekær, the InterCat center leader. "They might actively participate in early prebiotic chemistry, catalyzing further reactions that lead toward life."

"There’s still a lot to be discovered, but our research team is working on answering as many of these basic questions as possible," Sergio Ioppolo says. "We’ve already discovered that many of the building blocks of life are formed out there, and we’ll likely find more in the future."