https://en.wikipedia.org/wiki/Tholin
Tholins (after the Greek ???ό? (tholós) "hazy" or "muddy"; from the ancient Greek word meaning "sepia ink"
are a wide variety of organic compounds formed by solar ultraviolet irradiation or cosmic rays from simple carbon-containing compounds such as CO2, methane (CH
4) or ethane, often in combination with nitrogen (N2).[1] Tholins do not form naturally on modern-day Earth, but they are found in great abundance on the surface of icy bodies in the outer Solar System, and as reddish aerosols in the atmosphere of outer Solar System planets and moons.
When in the presence of water, tholins may facilitate the formation of prebiotic chemistry to take place, and has implication of the origins of life on Earth and possibly, on other planets. As particles in an atmosphere, tholins scatter light and can affect habitability.