A chemical engineer noticed that the spectra of the hazy atmosphere of mini-Neptune planets looked like the soot produced by combustion engines.

Most exoplanets might be 'soot factories,' scientists say: 'Like you have a natural diesel engine'

Source: space
Source Link: https://www.space.com/astronomy/exoplanets/most-exoplanets-might-be-soot-factories-scientists-say-like-you-have-a-natural-diesel-engine