In search of biosygnats, scientists have taken our planet's starting point, most of them are looking at gases that are found in large quantities, such as oxygen and methane, but what if they're not the only ones that support extraterrestrial life? In particular, researchers have studied nitrogen oxide, also known as hilarious gas.
Although 5,000 exoplanets have already been found, the search for life has been strengthened by, inter alia, the James Webb Space Telescope, which is able to investigate planetary atmospheres and search for biosympathies: traces of certain gases that can only be detected in the presence of extraterrestrial life, and is now mainly looking for traces of oxygen and methane, as N2 nitrogen is particularly difficult to detect, but a new study published in The Astrophysical Journal has just added a new element: nitrogen oxide.
According to researchers, "the coexistence of N2 and O2 in the atmosphere is a possible biosygnat" because, on the one hand, these two monoatomic molecules have a chemical imbalance and, on the other, only biological processes can produce a large amount of these gases.
Nitrogen cycle may be different on an exoplane
Initially created by numerous micro-organisms in the soil and oceans, nitrogen in our atmosphere today also comes from the burning of organic matter, fossil fuels, or even other industries; although the nitrogen cycle is disrupted as a result, it continues to operate according to the same pattern: nitrogen from the oceans and the atmosphere is detected by bacteria, transformed when they die and are then either absorbed by plant biomass and returned to the ground, or de-identified by bacteria and returned to the atmosphere.
At present, nitrogen oxides are mainly produced by human activities, especially agriculture, but will be produced mainly by denitriminating bacteria, of which either N2 or N2O are formed without human intervention," explains researchers.
According to researchers, however, it is possible that the last stage of denitrification, which changes N2O to N2, does not occur on other planets!," they explain. Indeed, if you go back far back to Earth's history, in the proterozoic era, the amount of N2O was much higher than today.
This was due to the lack of copper catalysts in the oceans, which prevented the final stage of the denitrification cycle! So one can imagine a similar process in other inhabited worlds, which calls into question the research that has been carried out to date. "This conclusion does not take into account periods in Earth's history when the conditions of the ocean allowed for much greater biological N2O emissions. The conditions of these periods may reflect the location of the exoplanet today," Schviterman says.
In addition, new mechanisms for the formation of nitrogen oxide may be in place in the oceans. ", says Eddie Schviterman, the first author of the study and astrobiologist from the University of California in Riverside, but under the right conditions in the ocean, some bacteria can turn these nitrates into N2O.
N2O is preferable in stars with low luminous intensity
To make sure of this, the research team did many simulations for a variety of different planets. Then they studied "," says the study.
All this is happening around different types of stars in the main sequence, from F-types to M-types, with preference given to smaller stars, because "low flows of star ultraviolets favour the accumulation of N2O", explained scientists. They found differences in the concentration of N2O by one or two order of magnitude compared to the concentration on Earth! Not "N2O escape", but enough to be detected in the average infrared range!
According to the study, the K-type orange dwarf stars or the M-type red dwarf stars are conducive to the emergence of a high concentration of N2O and to the maintenance of this level. For example, the Trumpist 1 system, which has an ultra-cold red dwarf as a host star and is going to explore the space telescope James Webb!, said Schviterman. The study, however, warns against false reactions: signatures that seem biological but are the result of abiotic processes. These signals conclude researchers "may be identified in the appropriate astrophysic and planetary context".