Lab-Based Studies Uncover Mechanism of Organic Compound Formation on Interstellar Ice

Researchers at Hokkaido University and The University of Tokyo have conducted laboratory experiments to gain insights into how carbon atoms diffuse on the surface of interstellar ice grains to form complex organic compounds. Their findings, published in the journal Nature Astronomy, shed light on the chemical complexity of the universe and have implications for understanding the origins of life.

Interstellar space contains a variety of organic molecules, and scientists are keen to understand how they interact and contribute to the building blocks of life. While direct observations have expanded our knowledge of these molecules, laboratory experiments are also crucial in unraveling the complex processes involved.

The researchers recreated interstellar conditions in the lab and detected carbon atoms diffusing and reacting on the surface of ice grains, leading to the formation of diatomic carbon (C2). This molecule is solid evidence for the presence of diffusing carbon atoms on interstellar ice grains. The study also revealed that diffusion could occur at temperatures above 30 Kelvin (minus 243 °C/minus 405.4 °F) and that in space, carbon atom diffusion could be activated at just 22 Kelvin (minus 251 °C/minus 419.8 °F).

According to lead author Masashi Tsuge, these findings bring a previously overlooked chemical process into the picture, showing how more complex organic molecules could be built through the addition of carbon atoms. This mechanism could occur in protoplanetary disks around stars, as well as in translucent clouds, which transition into star-forming regions. These processes may have played a role in seeding life on Earth.

This research expands our understanding of the formation of complex organic chemicals in space and highlights the various chemical reactions that contribute to carbon-based chemistry throughout the universe.

“Surface diffusion of carbon atoms as a driver of interstellar organic chemistry” by Masashi Tsuge, Germán Molpeceres, Yuri Aikawa, and Naoki Watanabe, 14 September 2023, Nature Astronomy.
DOI: 10.1038/s41550-023-02071-0