Published Wednesday in the Science Advances journal, the study examined the history of life on Earth to determine times when the planet's atmosphere contained gases "that are out of equilibrium" and could only exist with the presence of living organisms. Once determining said gases, researchers proposed in their work that they could use their findings to detect life on exoplanets.
Scientists ultimately concluded that if carbon dioxide and methane are detected together, without the presence of carbon monoxide, it would provide enough of a chemical imbalance to potentially signal the presence of life.
"We need to look for fairly abundant methane and carbon dioxide on a world that has liquid water at its surface, and find an absence of carbon monoxide," David Catling, a co-author in the study, said in a statement. "Our study shows that this combination would be a compelling sign of life."
"What's exciting is that our suggestion is doable and may lead to the historic discovery of an extraterrestrial biosphere in the not-too-distant future," he added.
But the point of the study also isn't to knock out the oxygen theory, says Joshua Krissansen-Totton, a fellow researcher involved in the study. It's more to offer another approach in the search for life abroad.
"This idea of looking for atmospheric oxygen as a biosignature has been around for a long time. And it's a good strategy — it's very hard to make much oxygen without life," Krissansen-Totton said in a statement. "But we don't want to put all our eggs in one basket."
"Even if life is common in the cosmos, we have no idea if it will be a life that makes oxygen," the researcher added. "The biochemistry of oxygen production is very complex and could be quite rare."
According to the researchers, NASA could test out the study findings once its high-powered telescopes, such as the James Webb Space Telescope, come online. By using the telescope's spectroscopy capability, which measures both radio waves and light, scientists could search for the specified gases, as they both "emit distinct wavelengths of light."
However, study researchers may have to wait a bit, as the Webb telescope isn't expected to go online until 2019. It's also scheduled to examine exoplanets such as the TRAPPIST-1 system, according to Business Insider.
