Artistic vision of the planet Kepler-186f, which revolves around the inhabited zone of the red dwarf
The new study suggests that oxygen is not a convincing sign of alien life, as astrobiologists thought earlier. Scientists conducting laboratory experiments with various types of simulated exoplanetary atmospheres were able to generate oxygen, as well as organic molecules with carbon — the chemical building blocks of life.
Most of the molecular oxygen (O2) in the Earth’s atmosphere (20% of our air) is pumped out by plants and photosynthesizing microbes. Therefore, astrobiologists and planetologists have long perceive oxygen as a key goal in the search for alien life. For example, many researchers are convinced that the presence of oxygen and methane in the atmosphere of another world is a strong indicator of biological activity.
The bottom line is that the two gases are not able to coexist for a long time, so the joint presence hints at the process of constant updating. Methane, like oxygen, is considered a common metabolic by-product on Earth, so it is reasonable to assume that its renewal indicates the presence of life. But such a find will not be able with 100% confidence to prove the presence of life on the planet. Part of the uncertainty arises from a lack of understanding of the exoplanets, on which oxygen and methane (or other potential biogatches) were found. Perhaps, in such a world some strange abiotic chemistry occurs, imitating the atmospheric signals that life produces on our planet.
The new study believes that such concerns are fully justified. Scientists have worked with nine different gas mixtures, corresponding to those found in the atmospheres of super-Earths or mini-Neptunes. The mixtures (carbon dioxide, water, methane and ammonia) were subjected to a temperature of 27 ° C-370 ° C, and one of two types of reaction-stimulating energy was added — ultraviolet light and plasma.
Each mixture was tested after three days and compounds were identified using a mass spectrometer. It turned out that with various combinations it was possible to obtain oxygen and organic substances, such as formaldehyde and hydrogen cyanide.