14 DAY TRIAL // The orange-brownish-colored atmosphere of Saturn's largest moon, Titan, surrounds the only known solar system bodies, except Venus and Earth, that have a solid surface and thick atmosphere. The hazy layer of gas covering the large rock features some peculiar reactions, as evidenced by the fact that the natural satellite itself supports lakes of liquid hydrocarbons on its surface. Experts from the University of Hawaii in Manoa (UHM) took it upon themselves to unravel the chemical evolution of Titan's atmosphere, in a setup that allowed for consequences of a single collision between molecules to be followed.
Led by physical chemist Ralf Kaiser, the team utilized crossed molecular beams for the job. The team learned that photodissociation was one of the most important processes going on in the moon's atmosphere. This is the process through which chemical compounds are broken down by photons in light waves. For instance, the experts found, UV radiations broke down acetylene, and created the ethynyl radical. This radical then collides with a diacetylene molecule, and forms triacetylene, one of the weird substances in Titan's heavy atmosphere.
“Surprisingly, the photochemical models show inconsistent mechanisms for the production of polyynes,” Kaiser, who is also the principal investigator of the new research, explains. Florida International University theoretical chemist Alexander Mebel also supports this method of obtaining triacetylene, which he obtained from theoretical calculations. In addition to the production method, Mebel's efforts also revealed the 3D distribution of electrons in the resulting atoms, as well as the overall energy level of the final molecules.
Further studies by experts at the Academia Sinica, in Taiwan, and the California Institute of Technology (Caltech), in California, additionally revealed that triacetylene might serve as one of the most basic building blocks for more complex and longer polyynes, which could in turn be the foundation for the chemicals required to create the aerosol-based layers of haze specific to the moon's atmosphere. In the future, this type of data will be combined with infrared observations of Titan, collected from the UHM Institute for Astronomy, and the Lowell Observatory, in Arizona.
Details of the new study appear in the latest online issue of the respected scientific journal Proceedings of the National Academy of Sciences (PNAS). The research, entitled “Chemical dynamics of triacetylene formation and implications to the synthesis of polyynes in Titan's atmosphere,” was only made possible by a grant from the US National Science Foundation (NSF).