Peptides, the Building Blocks of Life, Could Form on Interstellar Dust

[Avi Loeb Medium]

Illustration of glycine molecules on a surface of interstellar dust being bombarded by cosmic-ray protons (p+) to produce peptides, the building block of proteins and life-as-we-know-it. (Image Credit: Alfred Thomas Hopkinson et al. 2026, from a Nature Astronomy paper published here. The stars are adapted from Webb telescope image of the Cosmic Cliffs, NASA/ESA/CSA/STScI)

A new paper published in Nature Astronomy here, reports tantalizing results from laboratory experiments which demonstrate that the building blocks of proteins and life-as-we-know-it could form naturally on the surface of interstellar dust grains and are not, as previously thought, restricted to liquid-water chemistry on the surface of habitable Earth-like planets. This suggests that the `Lego-pieces’ for life could be assembled in the cold and rarefied environments of interstellar space and are ubiquitous in the Universe.

This realization is fully consistent with the discovery of protein-synthesizing amino acids and the five nucleobases used in RNA and DNA, within the material delivered to Earth from the asteroid Bennu by the OSIRIS-REx mission (as reported here).

The traditional notion for the origin of life on Earth was shaped by a landmark 1953 study (reported here) by Stanley Miller and Harold Urey who simulated early Earth’s conditions to show that simple organic molecules, like amino acids, could form spontaneously from inorganic precursors The experiment used methane (CH4), ammonia (NH3), hydrogen (H2), and water (H2O) and applied an electric spark — simulating lightning, to demonstrate the natural production of amino acids.

The new experiments were conducted at Aarhus University in Denmark and at the HUN-REN Atomki research facility in Hungary. The physical conditions encountered by interstellar dust particles were reproduced in an ultra-high vacuum chamber with a temperature as low as 13 degrees Kelvin above absolute zero (or -260 degrees Celsius).

Previous experiments already demonstrated that simple amino acids, like glycine, can form in interstellar space, but the new experiments demonstrated that more complex molecules, like peptides, could form naturally on the frigid surface of dust grains before these grains get incorporated into planets. Peptides are short chains in which individual amino acids link together. When peptides bond, they form proteins, which are essential for life. Identifying where and how protein precursors originate is a key step in figuring out the origin of life.

The new experiments placed glycine inside the vacuum chamber and exposed it to simulated cosmic-rays using an ion accelerator at HUN-REN Atomki. As a result of bombardment by energetic particles, the glycine molecules started reacting with each other to form peptides and water. This indicates that the protein production could occur on the surface of interstellar dust grains which coagulate to make rocks and planets in giant molecular clouds which serve as the nurseries of newly-born stars

If peptides are widespread on the surfaces of interstellar dust grains, then they can be easily delivered to the surface of habitable Earth-like planets — where the chemistry of life in liquid water can proceed. The reaction that links amino acids together into peptides follows the same basic rules of chemistry everywhere, making the early steps in the origin of life universal throughout the Milky-Way.

Nevertheless, the emergence of proteins is only one piece in the puzzle of life’s origin. Other pieces include membranes, nucleobases, and nucleotides, whose natural formation is actively studied in advanced laboratory experiments such as those carried by Jack Shostak at the University of Chicago (as described here).

Mainstream astronomers focus on the search for microbes beyond Earth. But as I often argue, it would be prudent to hedge our bets and also search for extraterrestrial intelligence at the same time. One of the benefits of discovering advanced extraterrestrial scientists is that they can educate us about the knowledge they acquired concerning the history of “Life in the Cosmos” (which happens to be the title of the textbook I co-authored here with my former postdoc, Manasvi Lingam in 2021). Dating someone smarter than us allows us to grow our knowledge base. As often is the case in science, the best is yet to come.

ABOUT THE AUTHOR

(Image Credit: Chris Michel, National Academy of Sciences, 2023)

Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.

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