Methylated gases could be an unambiguous indicator of alien life
On Earth, these gases are almost always produced only by organisms
![An illustration of an exoplanet passing in front of a star.](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2023/01/011023_jr_biosignatures_feat.jpg?fit=1030%2C580&ssl=1)
Light passing through the atmospheres of planets in distant solar systems (illustrated) could reveal compounds that alien organisms might make to protect themselves from toxic elements.
NASA's Goddard Space Flight Center