Atmospheres of exoplanets could hide signs of life

Planets tidally locked to their stars may have very different air flows than seen on Earth.
By Laurel Kornfeld | Nov 30, 2017
Chemical compounds that could indicate the presence of life on an alien planet might be more difficult to find than previously thought because unusual air flow patterns may hide them from observers.

This determination was made by a team of researchers who used computer models to simulate the nearest Earth-like planets, Proxima b and TRAPPIST-1d.

Both planets orbit low-mass red dwarf stars to which they are tidally locked, meaning one side always faces the star while the other always faces away from the star.

The latter condition could influence the way ozone is distributed in the planets' atmospheres. If air flows from their poles to their equators, the majority of their ozone--a variant of oxygen--could be directed to their equatorial reasons and trapped there, according to Ludmila Carone of the Max Planck Institute for Astronomy in Germany.

"Absence of traces of ozone in future observations does not have to mean there is no oxygen at all. It might be found on different places than on Earth, or it might be very well hidden," she stated.

Scientists plan to search for extraterrestrial life through telescopic observations of Earth-like planets' atmospheres. The presence of ozone could mean the plant is populated with life forms that produce oxygen, such as bacteria or even plants.

Any part of a planet not covered by a layer of ozone will be vulnerable to ultraviolet stellar radiation, which could potentially make that world uninhabitable.

"In principle, an exoplanet with an ozone layer that covers only the equatorial region may still be habitable," Carone said. "Proxima b and TRAPPIST-1d orbit red dwarfs, reddish stars that emit very little harmful UV light to begin with. On the other hand, these stars can be very temperamental, and prone to violent outbursts of harmful radiation, including UV."

Scientists hope to probe the atmospheres of exoplanets with the James Webb Space Telescope (JWST), set to launch in 2019.

Findings of the study were published in the journal Monthly Notices of the Royal Astronomical Society.


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