" Another readily detected biomarker is Earth's sustained level of the molecule methane, two thirds of which is produced by human-related activities...[including] burps and farts of domestic livestock. Natural sources...include decomposing vegetation in wetlands, and termite effluences. At this very moment, astrobiologists are arguing over the exact origin of...the copious quantities of methane on Saturn's moon Titan, where cows and termites we presume do not dwell. "

― Neil deGrasse Tyson , Astrophysics for People in a Hurry