Scientists have to devise novel ways to find potential life outside of planet Earth. One method that shows potentials in finding alien life is the use of biosignatures.

Chemical Disequilibrium

In a report published in the journal Science Advances, researchers said that they have found chemical combinations that may indicate the presence of biological activity on other planets.

Planetary scientist David Catling, the University of Washington in Seattle, and colleagues examined Earth's atmosphere as it existed during the Archean, Proterozoic, and Phanerozoic periods.

Life and Earth itself looked very different during each of these three different time periods. Despite the differences, each of these periods shares at least one characteristic: having chemical imbalances in the atmosphere.

Researchers attribute this to biological activities, which produce substances that should not otherwise coexist with each other. Examples of these compounds are methane and oxygen. They quickly react and destroy each other but both are abundant on the planet because living things produce them.

The researchers ran simulations of the known chemical content of each of the atmospheres during the different time periods on Earth to find out if there are telltale chemical disequilibrium that existed.

They found that there was little oxygen during the Archean. The coexistence of methane, carbon dioxide, and nitrogen in the atmosphere along with liquid water indicates that living things were working hard during this time period.

During the mid-Proterozoic, a combo of oxygen, nitrogen and liquid water hint of a growing number of oxygen-producing microbes. In the Phanerozoic, which includes the present day, biosignatures include oxygen with nitrogen and water.

"We show that methane mixing ratios greater than 10-3 are potentially biogenic, whereas those exceeding 10-2 are likely biogenic due to the difficulty in maintaining large abiotic methane fluxes to support high methane levels in anoxic atmospheres," the researchers wrote in their study.

"Biogenicity would be strengthened by the absence of abundant CO, which should not coexist in a biological scenario.

James Webb Space Telescope

Some of the chemical cocktails that may indicate hidden life could be detected by future observatories such as NASA's James Webb Space Telescope.

"James Webb is ideally suited for detecting methane and carbon dioxide, and so it could be the first opportunity to see the disequilibrium biosignature that we propose," said study researcher Krissansen-Totton, from the University of Washington. "However, we'll need to get lucky to see signs of life with JWST because it will only observe a small number of targets, and because observations of Earth-sized planets are very challenging to do, even with giant space telescopes."

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