A new approach to detecting oxygen in the atmospheres of planets beyond our solar system may aid in the search for life beyond Earth.
Researchers from the University of California, Riverside developed a new technique that will use NASA's James Webb Space Telescope (JWST), which is scheduled to launch in 2021, to study the atmospheres of exoplanets and look for signs that oxygen molecules have collided, according to a statement.
"Before our work, oxygen at similar levels as on Earth was thought to be undetectable with Webb," Thomas Fauchez, a planetary scientist at NASA's Goddard Space Flight Center in Maryland and lead author of the new study, said in the statement. "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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Oxygen is vital for life on Earth and is produced by organisms that use photosynthesis to convert sunlight into energy. Finding oxygen in the atmospheres of exoplanets may provide evidence that life also exists on those distant worlds, the researchers said. However, oxygen can also accumulate in the atmosphere of a planet that doesn't have any life at all.
By looking for the strong signals produced by colliding oxygen molecules, scientists hope that JWST will help them determine if nonliving processes produced the oxygen and, in turn, let them distinguish between exoplanets that harbor living processes and those that don't, according to the statement.
"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," Edward Schwieterman, co-author of the study and an astrobiologist at UC Riverside, said in the statement. "This technique will allow us to find oxygen in planets both living and dead."
Using the James Webb Space Telescope, the researchers will look for patterns of light in an exoplanet's atmosphere. When oxygen molecules collide, the event creates a strong signal that blocks parts of the infrared light spectrum from being seen by a telescope.
There are conditions in which oxygen molecules may be present in the atmosphere of an exoplanet that does not host life. For example, a planet that lies close to its host star or is exposed to a lot of starlight would have a warmer atmosphere. If there are oceans on the planet's surface, its atmosphere may become saturated with water vapor as the heat evaporates the oceans, the researchers said.
Strong ultraviolet radiation from the star would then break down the water molecules in the atmosphere, creating atomic hydrogen and oxygen. While the hydrogen atoms are light enough that they would escape into space, the oxygen molecules would be left behind. Over time, this process could cause an exoplanet to have a thick oxygen atmosphere.
Therefore, "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 in the statement.
Their findings were published Jan. 6 in the journal Nature Astronomy.
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