Future telescopes such as NASA’s James Webb Space Telescope (right) will observe atmospheres of exoplanets for signs of life. Oxygen/ozone reveal life on the modern Earth (top left). For the early Earth (bottom left), the combination of methane and carbon dioxide would provide an alternative biosignature, a new study suggests.  (J. Krissansen-Totton)

Alien-life hunters should keep an open mind when scanning the atmospheres of exoplanets, a new study stresses.

The time-honored strategy of looking for oxygen is indeed a good one, study team members said; after all, it’s tough for this gas to build up in a planet’s atmosphere if life isn’t there churning it out.

“But we don’t want to put all our eggs in one basket,” study lead author Joshua Krissansen-Totton, a doctoral student in Earth and space sciences at the University of Washington in Seattle, said in a statement. [5 Bold Claims of Alien Life]

“Even if life is common in the cosmos, we have no idea if it will be life that makes oxygen,” Krissansen-Totton added. “The biochemistry of oxygen production is very complex and could be quite rare.”

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