Astrobiology

An interstellar energetic and non-aqueous pathway to peptide formation

This study unveils a groundbreaking non-aqueous pathway for peptide formation in space, challenging traditional models of life's origins.

ResearchEP 24Paper
In plain English

Imagine you have a box of LEGO bricks, which are like the basic molecules of life called amino acids. To build anything, you need to snap them together. Scientists used to think you needed a puddle of liquid water to make the bricks 'click'. This experiment is like discovering you can snap the LEGOs together inside a freezer. The researchers took the simplest amino acid, froze it onto a dust grain like you'd find in space, and zapped it with energy that mimics cosmic radiation. They found that the amino acids linked up to form a two-brick chain, the first step towards building a protein. This means the essential first chains for life could be forming all over space and delivered to new planets by comets and asteroids.

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Key findings5
  1. 01

    Demonstrated peptide formation in interstellar ice analogues without liquid water.

  2. 02

    Confirmed peptide bond formation using infrared spectroscopy and mass spectrometry.

  3. 03

    Detected glycylglycine formation, the simplest dipeptide, under space-like conditions.

  4. 04

    Challenged aqueous-centric models of early biochemical evolution.

  5. 05

    Suggested potential for peptide formation in cold interstellar medium.

Abstract

The origin of the molecular building blocks of life is a central question in science. A few α-amino acids, such as glycine, the simplest proteinogenic amino acid, have been detected in meteorites and comets, indicating an extraterrestrial origin for some prebiotic molecules. However, the formation of peptides, short chains of α-amino acids linked by peptide bonds, has remained unresolved under astrophysical conditions. Here we show that the building blocks of proteins can form in interstellar ice analogues exposed to ionizing radiation without the presence of liquid water. Using isotopically labelled glycine irradiated with protons at cryogenic temperatures, we detect the formation of glycylglycine, the simplest dipeptide, along with deuterated and undeuterated water as by-products. The formation of peptide bonds is confirmed by infrared spectroscopy and high-resolution mass spectrometry, which also reveal the production of other complex organic species. These findings demonstrate a non-aqueous route to peptide formation under space-like conditions and suggest that such molecules could form in the cold interstellar medium and be incorporated into forming planetary systems. Our results challenge aqueous-centric models of early biochemical evolution and broaden potential settings for the origins of life.