American scientists have concluded that life on an exoplanet can exist even if oxygen is not present in its atmosphere, but instead methane, nitrogen, carbon dioxide and water vapor will be found.
In search of possible life on distant planets, experts are conducting spectroscopy of the atmosphere to determine its chemical composition. For a positive result, biosignatures must be found in the atmosphere - substances that indicate that living organisms can exist on the planet, writes Republic.
Until recently, the main biosignature that researchers were looking for on planets was oxygen. However, experts from the University of Washington and the University of California have proven that the absence of oxygen, but the presence of a combination of other biosignatures, can also be sufficient for the emergence of life. They presented an explanation of their theory in the journal Science Advances.
To substantiate their idea, scientists modeled the Earth's atmosphere during the Archean (4–2.5 billion years ago) and Proterozoic (2.5–0.5 billion years ago), when there was no oxygen atmosphere on the planet, but the first organisms were already existed. The results showed that the presence of sufficient amounts of methane and carbon dioxide in the atmosphere, as well as the presence of liquid water, could be a sign of life on the planet. For example, methane and carbon dioxide can appear without living organisms - due to volcanic eruptions or collisions with asteroids.
Earlier, chemists from the Scripps Research Institute in the United States developed a fascinating theory according to which life on Earth originated 4 billion years ago thanks to looped chemical reactions.