The new study suggests that oxygen does not have to be a sign of extraterrestrial life as convincing as astrobiologists thought.
Researchers conducting laboratory experiments with different types of simulated exoplanet atmosphere have managed to create oxygen as well as organic molecules that contain carbon, the basic building elements of life we know them.
"People have said that the presence of oxygen and organic compounds has shown life, but we have abiotically produced them in multiple simulations," said chief engineer Chao He of the Earth Science and Planetology University of Johns Hopkins, Baltimore. "It suggests that even the simultaneous presence of universally accepted biosignatures can be fake positive for life." [10 exoplanets that can be received by aliens]
The vast majority of molecular oxygen (O2) in the Earth's atmosphere - and the substance is about 20% of our air - pumping plants and photosynthesis microbes. So astrobiologists and planetary scientists have long considered oxygen to be a key target in pursuit of extraterrestrial life.
For example, many researchers argue that the discovery of oxygen and methane in the atmosphere of an exoplanet was a powerful indicator of biological activity. Since these two gases cannot coexist for a long time, their combined presence suggests a continuous renewal. And since methane, as well as oxygen, a common metabolic byproduct on Earth, rebuilding through life would seem a reasonable conclusion.