“Tholins” designates the solid refractory organics that are produced during the irradiation of gases or ice mixtures of simple compounds by a variety of energy sources, which are also of astrophysical significance.
The word tholins was coined by Carl Sagan and Bishun Khare in the late 1970s (Sagan and Khare 1979), when they realized that in many laboratory experiments, simulating the chemical evolution of astrophysical environments starting from simple organic compounds, nonvolatile complex macromolecular organics were systematically formed. They proposed in particular that tholins play a key role in the organic chemistry of interstellar grains and gas. Since these products often looked like mud or tar, Sagan and Khare decided to call them “tholins,” which comes from the Greek word “tholos,” meaning “muddy” or alternatively “domed.”
Tholins are produced in a large variety of experiments simulating the complexification of...