Cosmic rays could be origin of handedness

A paper published in Astrophysical Journal Letters by a Stanford professor and a post-doctoral scholar suggests that the interaction between cosmic rays and organic matter may be responsible for biological chirality. 

If their suspicion is correct, it's possible that all life in the universe shares the same chiral preference, according to a press release from Stanford.

Chirality, or handedness, is the existence of mirror-image versions of molecules, according to the press release. They are similar in appearance but do not line up if stacked together. All major biomolecules use a particular form of handedness. If the mirror version of a molecule is used, systems malfunction or fail completely. 

Biological homochirality was first discovered by Louis Pasteur in 1848, according to Stanford. He hypothesized that if life is asymmetric, it may be due to physical asymmetry in the cosmos. Since then, scientists have debated whether the handedness of life was random or caused by an unknown influence. 

“We propose that the biological handedness we witness now on Earth is due to evolution amidst magnetically polarized radiation, where a tiny difference in the mutation rate may have promoted the evolution of  DNA-based life, rather than its mirror image,” Noémie Globus, lead author of the paper and a former Koret Fellow at the Kavli Institute for Particle Astrophysics and Cosmology, told the Stanford News Service press release.

The researchers argue in favor of cosmic rays, high-energy radiation from various sources throughout the universe, as the origin of homochirality. Once in the earth's atmosphere, cosmic rays degrade into fundamental particles, according to the release.

Muons, cosmic rays at ground level, are magnetically polarized and decay into electrons with the same polarization. Researchers believe that muons and their daughter electrons can affect chiral molecules on earth and throughout the universe.

“We are irradiated all the time by cosmic rays,” Globus told Stanford. “Their effects are small but constant in every place on the planet where life could evolve and the magnetic polarization of the muons and electrons is always the same. And even on other planets, cosmic rays would have the same effects.”

The researchers hypothesize that in Earth's beginning, the constant radiation from cosmic rays affected mirror life-forms, allowing one to prevail over the other, according to the press release. The chiral influence from cosmic rays could have produced the single biological handedness seen today.

Globus and Roger Blandford, the Luke Blossom professor in the School of Humanities and Sciences at Stanford and an author on the paper, also suggest some experiments they would like to perform to validate their cosmic ray hypothesis. One experiment would be to test how bacteria respond to radiation with different magnetic polarization. They are also looking forward to testing organic samples from comets, asteroids or Mars, according to the press release. 

“This idea connects fundamental physics and the origin of life,” Blandford told the Standford News Service. “Regardless of whether or not it’s correct, bridging these very  different fields is exciting and a successful experiment should be interesting.”