Researchers used laboratory experiments to recover chemical steps leading to the formation of complex hydrocarbons in space. A recent analysis from the Lawrence Berkeley Lab tried to explain the presence of pyrene (a chemical compound known as polycyclic aromatic hydrocarbon) in some meteorites.
Scientists believe that some of the first carbon structures underwent evolution in space. Starting with simple gases, one-dimensional and two-dimensional structures can be created. Pyrene leads to two-dimensional graphene, followed by graphite and the evolution of more complex chemistry.
The molecular structure of pyrene is represented by 16 carbon atoms and 10 hydrogen atoms. It turned out that the same thermal processes leading to the creation of pyrene are also carried out in combustion processes in automobile engines, as a result of which soot particles appear.
The latter study is based on earlier works, where they analyzed hydrocarbons with smaller molecular rings, observed in space. When they were first noticed, it was not clear how they appeared. This question forced astronomers and chemists to join forces to understand how the chemical precursors of life in space were formed. Pyrene belongs to the family of polycyclic aromatic hydrocarbons (PAHs), which account for about 20% of all galactic carbon. PAHs are organic molecules consisting of a sequence of fused molecular rings.
Scientists examined chemical reactions associated with the combination of a complex hydrocarbon radical 4-phenanthrene, whose molecular structure includes a sequence of 3 rings and contains 14 carbon atoms and 9 hydrogen atoms with acetylene.
The gas mixture was introduced into the microreactor, which heated the sample to high temperatures in order to simulate stellar conditions. The device generates light rays from IR to X-rays. The mixture came out through a tiny nozzle at supersonic speeds, which made it possible to stop the active chemistry in the heated cell. The team then focused a beam of vacuum UV light from the synchrotron to the heated gas mixture.
The detector of the charged particles measured the different arrival times of the particles formed after ionization. They contained the control signatures of the parent molecules. Experimental measurements and theoretical calculations allowed us to see the intermediate chemical steps and confirm the creation of pyrene. In future studies, they plan to study methods for the formation of larger annular molecules with the same technique.