Scientists Search for Signatures of Alien Life Hidden in Gas

Huddled in a coffee shop one drizzly Seattle morning six years ago, the astrobiologist Shawn Domagal-Goldman stared blankly at his laptop screen, paralyzed. He had been running a simulation of an evolving planet, when suddenly oxygen started accumulating in the virtual planet’s atmosphere. Up the concentration ticked, from 0 to 5 to 10 percent.

“Is something wrong?” his wife asked.

“Yeah.”

The rise of oxygen was bad news for the search for extraterrestrial life.