So does Europa and Titan. They were found in the comet ice on which ESA NASA landed a probe. Rosetta's Philae lander successfully made the first soft landing on a comet nucleus when it touched down on Comet Churyumov–Gerasimenko on 12 November 2014.

Tholins are organic compounds and building blocks of amino acids. Chains of amino acids form from tholins when exposed to UV light, or electrocomagnetism. Terrestrial bombardment by comets during the Hadean are responsible for terrestrial water.