Touted as a “biosignature” on an alien planet, dimethyl sulfide also seems to arise in banal ways

A team of astronomers claims to have sniffed out a “biosignature” in the atmosphere of a distant planet called K2-18b. But not everyone agrees that it signals life.

Recent controversies bode ill for the effort to detect life on other planets by analyzing the gases in their atmospheres.

Samples from Bennu contain the chemical building blocks of life — but with a twist.