That complexity hints at the challenge of searching for life as we don't know it—the alien biology that might have taken hold on other planets, where conditions could be unlike anything we've seen before.
Studies by the James Webb Space Telescope (JWST), set to launch next year, will reveal whether we should rule out these worlds, too.
For the motley bunch of exoplanets that have no analog in our solar system, however, scientists have to rely on laboratory experiments and sheer imagination.
"We're still looking for the basic physical and chemical requirements that we think life needs, but we're trying to keep the net as broad as possible," Cable said.
Exoplanet researchers such as Sara Seager at the Massachusetts Institute of Technology and Victoria Meadows at the University of Washington are modelling disparate types of possible planetary atmospheres and the kinds of chemical signatures that life might imprint onto them.