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Astronomers develop better way to detect oxygen in alien atmospheres

Some astronomers theorize that water worlds located close to their host stars could produce oxygen-rich atmospheres without being hospitable to life. Photo by NASA/ESA/M. Kornmesser
Some astronomers theorize that water worlds located close to their host stars could produce oxygen-rich atmospheres without being hospitable to life. Photo by NASA/ESA/M. Kornmesser

Jan. 7 (UPI) -- Scientists have developed a new way to detect oxygen in the faraway atmospheres of exoplanets, a breakthrough that could aid the search for alien life.

Oxygen exists naturally in the universe, but its presence in large quantities is theorized by some scientists to be rare. On Earth, an abundance of oxygen is produced by living organisms like plants, algae and cyanobacteria, which use photosynthesis to turn sunlight into energy.

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Scientists on the hunt for habitable planets and signs of life on exoplanets remain on the lookout for elevated oxygen levels, but studying chemical composition of distant atmospheres remains quite difficult.

Astronomers have pinned much of the hope for characterizing the atmospheres surrounding distant exoplanets on the James Webb Telescope. But not everyone is convinced of the space telescope's potential.

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Now, in a new study published this week in the journal Nature Astronomy, scientists have detailed a new technique for using NASA's James Webb Space Telescope to detect faraway oxygen molecules

"Before our work, oxygen at similar levels as on Earth was thought to be undetectable with Webb," lead study author Thomas Fauchez, researcher at NASA's Goddard Space Flight Center, said in a news release. "This oxygen signal is known since the early 1980s from Earth's atmospheric studies but has never been studied for exoplanet research."

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For the new study, scientists calculated how much infrared light is absorbed by collisions between oxygen molecules. By measuring collision-induced absorptions in the infrared, authors of the new study claim James Webb will be able to help astronomers estimate oxygen levels in the atmospheres of distant exoplanets.

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More than just help scientists detect oxygen, the new technique could help researchers determine the value of oxygen as a marker for life.

There are problems with interpreting elevated oxygen as a signpost for life. Some astronomers estimate oxygen could accumulate naturally in the atmospheres of exoplanets without living organisms.

To put this theory to the test, scientists would need to study oxygen levels in the atmospheres surrounding both potentially habitable and obviously uninhabitable exoplanets.

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"Oxygen is one of the most exciting molecules to detect because of its link with life, but we don't know if life is the only cause of oxygen in an atmosphere," said UC Riverside astrobiologist Edward Schwieterman. "This technique will allow us to find oxygen in planets both living and dead."

Some astronomers theorize that exoplanets with intimate orbits around their host stars and rapidly evaporating oceans could host atmospheres filled with water vapor. Ultraviolet radiation could split water vapor into oxygen and hydrogen, with hydrogen atoms more likely to be lost to space -- thus, leaving behind a concentration of oxygen.

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"It is important to know whether and how much dead planets generate atmospheric oxygen, so that we can better recognize when a planet is alive or not," Schwieterman said.

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