Peptides on interstellar ice: Study finds presence of water molecules not major obstacle to formation

A research team led by Dr. Serge Krasnokutski from the Laboratory of Astrophysics at the Max Planck Institute for Astronomy at the University of Jena has demonstrated that simple peptides can form on cosmic dust grains. However, it was previously thought that this was not possible if the molecular ice covering the dust grains contained water (which it usually is).

Now, the team, working with the University of Poitiers in France, has discovered that the presence of water molecules is not a major obstacle to the formation of peptides on such dust particles.The researchers report their findings in the journal scientific progress.

Chemistry in the icy vacuum

“We replicated conditions similar to those in outer space in a vacuum chamber and also added substances from so-called molecular clouds,” explains Krasnokutsky. These substances include ammonia, atomic carbon, and carbon monoxide. “Thus, all the chemical elements required for a simple peptide are present,” the physicist added.

Krasnokutsky described that these raw materials initially formed chemical precursors of amino acids called aminoketenes. They then combine to form chains, producing polypeptides. “It was previously suspected that single aminoketenes would combine to form peptides,” the scientists explained

“However, for this step, the absence of water may be crucial, as it may hinder the reaction. At the same time, most interstellar dust grains are covered in water-containing molecular ice,” Krasnokutsky said. Therefore, the hypothesis so far is that if peptides are formed in space, they are formed to a limited extent.

French precise analysis

“However, high-precision mass spectrometry analysis now available at the University of Poitiers shows that the presence of water in the molecular ice slows down the formation of peptides by fifty percent, but they are still formed,” he explains. “When you consider the timescales on which astronomical processes occur, this slowdown is actually negligible.”

The question of whether our planet’s first biomolecules originated from terrestrial or extraterrestrial sources (or both) is likely to remain open for the foreseeable future. However, as this discovery shows, outer space cannot be ruled out as the source of our life.