The fundamental chemistry behind life on Earth may have originated not in warm oceans or hydrothermal vents, but in the frigid depths of interstellar space. A new study reveals that peptides – the molecular chains essential for proteins – can form within icy dust grains exposed to cosmic radiation, a process previously considered impossible. This discovery reframes our understanding of how life’s precursors arose and expands the range of environments where life could potentially emerge.
The Long-Standing Mystery of Peptide Formation
For years, scientists have known that simple organic molecules exist in interstellar clouds and meteorites. However, a crucial gap in the story remained: how amino acids, the building blocks of proteins, could link together in the harsh vacuum of space to create peptides. Liquid water was long assumed to be a necessary component for these reactions, but this new research demonstrates an alternative pathway.
How Space Ice Drives Chemical Reactions
Researchers at Aarhus University simulated space-like conditions in a laboratory, freezing glycine (a simple amino acid) to a cryogenic temperature of -260°C (-436°F). They then bombarded the frozen sample with high-energy protons, mimicking cosmic rays. The result? The formation of glycylglycine, the simplest possible dipeptide.
This process shows that ionizing radiation can provide enough energy to break and reform chemical bonds, allowing amino acids trapped in ice to link together without the need for liquid water. “All types of amino acids bond into peptides through the same reaction,” explains co-author Alfred Thomas Hopkinson. “It is therefore very likely that other peptides naturally form in interstellar space as well.”
Beyond Water: A New Understanding of Prebiotic Chemistry
The team also observed the formation of both ordinary water and deuterium-enriched water, alongside a variety of other complex organic molecules. This finding challenges the conventional wisdom that complex molecules only form later in the star and planet formation process. Instead, it suggests that the building blocks of life are created much earlier, within cold, dense interstellar clouds.
Implications for the Search for Extraterrestrial Life
The implications are profound: if peptides can form in space, they could be delivered to rocky planets within newly formed solar systems. This means that life’s precursors aren’t limited to warm, wet environments on Earth. The discovery broadens the search for extraterrestrial life, suggesting that life might emerge in environments previously considered inhospitable.
“Eventually, these gas clouds collapse into stars and planets… If those planets happen to be in the habitable zone, then there is a real probability that life might emerge.” – Sergio Ioppolo, Aarhus University.
While the exact origins of life remain unknown, this research shows that many of the necessary molecules are created naturally in space. The team is now working to identify other peptides and complex organic molecules that may form under similar conditions. This is a crucial step towards understanding how life could arise in the vast, cold universe.
