According to the authors of the study, the data obtained expands our understanding of the origins of life and clarifies the mechanism of "interstellar factories" in the synthesis of organic molecules.
According to experts, about three million tonnes of interstellar dust, consisting not only of minerals, but also of rather complex organic matter, such as hydrocarbons and their derivatives, annually falls to the Earth. The reactions leading to the formation of organic compounds in space are still poorly studied. The key feature of such reactions is accessibility, meaning that they occur in the complete absence of external energy sources, which makes them extremely rare and demanding on the composition of reagents. Under terrestrial conditions, the formation of organic matter is much easier due to the variety of chemical compounds and the ability to obtain heat from the environment.
In their study, the group of scientists from Samara University attempted to demonstrate for the first time how the simplest polycyclic aromatic hydrocarbon (PAH), indene, can be formed at temperatures similar to those found in outer space.
"Small solid hydrocarbon particles containing PAHs, commonly known as interstellar grains, act like molecular cosmic factories for the synthesis of organic [materials] such as aminoacids or sugars. We have identified the elementary steps that lead to PAH formation in space. It's crucial for the understanding of the chemistry of carbonaceous matter in our galaxy", Galia Galimova, one of the authors of the study, and graduate student at Samara University said.
According to the scientists, small non-biological molecules gathered on the surface of interstellar grains, can react with each other, thereby producing a chemical "assembly" of more complex biological molecules. Grains with such molecules, drifting through interstellar space, can find their way to favourable conditions, where, according to the scientists, life can occur based on them.
"The reaction we have described takes place between a styrene molecule and a methylidyne radical. It results in its intermediate state, which cyclises and subsequently leads to the formation of indene and atomic hydrogen", Galia Galimova stated.
There are currently no alternatives to the described mechanism of indene formation in space, the researchers said. Another known barrier-free reaction leading to indene formation is the reaction between gasoline and an allyl molecule, but both of these compounds are unstable and have not been detected in deep space.
The astrochemical modeling of the reaction carried out fully confirmed its possibility under conditions found in space.
The study was carried out in close collaboration with specialists from the University of Hawaii at Manoa, Florida International University, and Benedictine College in Atchison (USA). The research team intends to continue studies in this area in the future.