Formation of organic compounds in interstellar ice

2023-09-15 16:15:08

Knowing how organic (carbon-based) chemistry develops in interstellar space is essential to finding out how life arose on Earth and how it may have done so on other worlds. This knowledge would also allow more reliable estimates to be made about how many planets in our galaxy can support life.

The list of organic substances detected in space and the knowledge about how they could be interacting continue to increase thanks to increasingly better direct observations. But laboratory experiments that unravel complex processes can also offer significant clues.

Following this last strategy, a team led by Masashi Tsuge, from Hokkaido University in Japan, has carried out experiments on the interaction, in interstellar space, of carbon atoms with ice grains.

Some of the most complex organic molecules in the cosmos are thought to be produced on the surface of interstellar ice grains at very low temperatures. Ice grains suitable for this purpose are known to be abundant throughout the universe.

All organic molecules are based on a skeleton of linked carbon atoms. Most carbon atoms were originally formed through nuclear fusion reactions in stars, eventually dispersing across interstellar space when stars died in supernova explosions. But to form complex organic molecules, carbon atoms need a mechanism that allows them to meet on the surface of ice grains, thus creating chemical bonds between such atoms. The new research suggests a feasible mechanism for this.

Artist’s recreation of the concept of the formation of organic compounds in interstellar ice particles. (Image: Masashi Tsuge)

The authors of the study, by recreating interstellar conditions in the laboratory, have managed to detect weakly bonded carbon atoms that diffuse across the surface of the ice grains until the reactions produce molecules of what is known as diatomic carbon. A molecule of this type is made up of two linked carbon atoms. The formation of diatomic carbon clearly reveals the diffusion of carbon atoms on interstellar ice grains.

The new study indicates that a previously overlooked chemical process could explain how more complex organic molecules can be formed by the constant addition of carbon atoms.

The authors of the study believe that this and other processes could occur in the protoplanetary disks around stars, from which planets form. This could also explain the origin of the chemicals that, according to all indications, served as precursors to life on Earth.

The study is titled “Surface Diffusion of Carbon Atoms as a Driver of Interstellar Organic Chemistry.” And it has been published in the academic journal Nature Astronomy. (Source: NCYT from Amazings)