Will Webb Be Able To Detect Oxygen In The Atmosphere Of An Exoplanet?

New Technique May Give NASA’s Webb Telescope a Way to Quickly Identify Planets with Oxygen.

NASA’s James Webb Space Telescope may be able to quickly detect nearby planets that could be promising for our quest for life, as well as those that are uninhabitable because their seas have melted, according to researchers.

Exoplanets (planets orbiting other stars) are too far away for scientists to visit in order to seek for signs of life. Instead, they will have to rely on cutting-edge telescopes like Webb to peer into extraterrestrial atmospheres.

Why Is Oxygen Important?

The existence of oxygen in an exoplanet’s atmosphere is one possible indicator of life, or biosignature. When organisms like plants, algae, and cyanobacteria employ photosynthesis to turn sunlight into chemical energy, they produce oxygen.

What Should Webb Search For To See If A Planet Has A Lot Of Oxygen?

Researchers discovered a powerful signal produced by oxygen molecules colliding in a recent study. According to scientists, Webb has the ability to detect this signal in extraterrestrial atmospheres.

“Oxygen at similar amounts to those found on Earth was assumed to be undetected with Webb before our work, but we discovered a promising technique to detect it in adjacent planetary systems,” said Thomas Fauchez of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“This oxygen signal has been known from Earth’s atmospheric studies since the early 1980s, but it has never been investigated for exoplanet research.” Fauchez is the study’s principal author, and it was published in the journal Nature Astronomy on January 6th.

How Did Scientists Observe Oxygen?

By simulating the atmospheric conditions of an exoplanet orbiting a M dwarf, the most common form of star in the cosmos, the researchers were able to reproduce this oxygen signature.

M dwarf stars are much smaller, cooler, and fainter than our Sun, yet they are far more active, generating powerful ultraviolet light as a result of explosive activity.

The scientists simulated how the component colors of the star’s light would change when the planet passed in front of it by modeling the influence of this increased radiation on atmospheric chemistry.

Why Is Oxygen So Unique In Exoplanets?

The oxygen in the exoplanet’s atmosphere absorbs particular colors (wavelengths) of light as it passes through it, in this case infrared light with a wavelength of 6.4 micrometers. When oxygen molecules hit each other or with other molecules in the exoplanet’s atmosphere, the energy from the impact causes the oxygen molecule to enter a unique state that allows it to absorb infrared light for a short period of time.

How Can Infrared Help?

Infrared light is undetectable to the naked eye, but it can be detected with telescope-mounted sensors.
“Similar oxygen signals exist at 1.06 and 1.27 micrometers and have been discussed in previous studies,” said Geronimo Villanueva, a co-author of the paper at Goddard. “However, these are less strong and much more mitigated by the presence of clouds than the 6.4 micrometer signal.”

Surprisingly, oxygen can make an exoplanet appear to have life even if it doesn’t, because it can build in the atmosphere even if there is no life there.

The atmosphere becomes highly heated and saturated with water vapor from evaporating seas if the exoplanet is too close to its host star or receives too much stellar radiation. This is because hydrogen is a light atom, it can quickly escape into space, leaving oxygen behind.

Over time, this process can result in the loss of entire seas while simultaneously creating a rich oxygen atmosphere.

As a result, high oxygen in an exoplanet’s atmosphere does not always imply abundant life, but it could indicate a long history of water.

“We can get a notion of how likely it is that the planet is habitable based on how easily Webb detects this 6.4 micrometer signal,” said Ravi Kopparapu, a co-author of the work at Goddard. “If Webb points to a planet and easily catches this 6.4 micrometer signal, it’s likely that the planet has a dense oxygen atmosphere and is inhospitable.”

Why Is the Oxygen Signal From My Dwarf So Important?

The oxygen signal is so powerful that astronomers can use just a few Webb transit images to determine if M dwarf planets have atmospheres at all.

“This is significant because M dwarf stars are extremely active, and it has been hypothesized that stellar activity might ‘blow away’ entire planetary atmospheres,” Fauchez explained.

“Understanding star-planet interactions around these abundant yet active stars requires merely knowing whether a planet orbiting a M dwarf can have an atmosphere at all.”

Despite the strength of the oxygen signal, cosmic distances are enormous and M dwarfs are dark, thus Webb will need to discover the signal in exoplanet atmospheres in a reasonable amount of time.

An exoplanet with a current Earth-like atmosphere would have to be orbiting a M dwarf within 16 light-years of the Earth.

The signal might be detected up to 82 light-years away from a dehydrated exoplanet with an oxygen atmosphere 22 times the pressure of Earth’s. One light-year is almost six trillion miles, which is the distance light travels in a year.


The nearest stars to our Sun are roughly 4 light-years away in the Alpha Centauri system, while our galaxy is around 100,000 light-years across.

Goddard’s Sellers Exoplanet Environments Collaboration (SEEC), which is partially sponsored by NASA’s Planetary Science Division’s Internal Scientist Funding Model, contributed to the research.

Marie Sklodowska-Curie Grant, the NASA Astrobiology Institute Alternative Earths team, and the NExSS Virtual Planetary Laboratory have also contributed to this project.

Launched in Dec, 2021 Webb will be the world’s most advanced space research observatory. It will look beyond our solar system to distant worlds orbiting other stars, and it will investigate the unfathomable architecture and origins of our universe and our place in it.

Webb is a NASA-led international project involving ESA (European Space Agency) and the Canadian Space Agency as partners.

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