Why do hydrocarbons exist on other planetary bodies, like Titan, a moon of Saturn?

Did they have fossils also?

Hydrocarbons on Titan…

The main atmospheric constituents of Titan are nitrogen and methane, with trace amounts of other gases such as hydrogen and acetylene. The process of photochemical dissociation, where ultraviolet radiation breaks apart methane molecules, leads to the formation of a variety of hydrocarbon species. These hydrocarbons can then undergo…