Astronomers have suggested that phosphine, supposedly recorded in the Venusian atmosphere last year, got there not because of the existence of life on the planet, but because of explosive volcanic eruptions. The research results were published in the scientific journal Proceedings of the National Academy os Sciences.
"Traces of phosphine in the atmosphere of Venus tell us not that there is life in its clouds, but about what is happening in its depths. All the data we have indicates that Venus is recently or even now undergoing explosive volcanic eruptions," - said one of the authors of the study, professor at Cornell University, Jonathan Lunin.
At the end of September last year, planetary scientists said that they saw in the spectrum of the upper atmosphere of Venus, at an altitude of about 50-60 km, traces of phosphine - a gaseous compound of phosphorus and hydrogen. At this height, there are relatively warm clouds, which contain a lot of water and relatively few chemically aggressive compounds.
By its nature, this gas is unstable, on Earth it is formed only as a result of processes associated with living organisms. Therefore, astronomers suggested that similar microbes could be its source on Venus. This is also supported by the fact that in the same clouds, scientists have found hints of the existence of complex compounds, which in their spectral properties are similar to proteins.
Subsequently, some astronomers questioned the discovery of phosphine, while other scientists tried to re-discover its traces, but could not do so. Therefore, many scientists believe that "traces" of phosphine are likely to represent random interference or measurement error.
However, Lunin and his colleagues decided to proceed from the fact that there is indeed phosphine in the planet's atmosphere, but the reason for its appearance may be different. According to the results of the new study, they offered an alternative explanation for how this gas could have appeared in the atmosphere of Venus, as well as why astronomers did not find traces of it during repeated observations.
The researchers assumed that a fairly large amount of phosphine is formed on Earth during certain types of volcanic eruptions. Its source is compounds of phosphorus and metals from the rocks of the deep layers of the mantle. They are converted to phosphine in a series of complex reactions with sulfuric acid and other volatile substances that are also found in volcanic emissions. And in the cloudy layer of the atmosphere of Venus, sulfuric acid is even more.
Calculations of planetary scientists show that the eruptions of Venusian volcanoes, comparable in power to the explosion of Mount Krakatoa in 1883, can raise a sufficiently large amount of phosphorus and metal compounds to the height where the presence of phosphine was initially suspected. There, these compounds can interact with sulfuric acid and generate phosphine. After the eruption is over, the gas concentration will rapidly decrease. As a result, traces of this gas will appear and disappear periodically - depending on whether there are powerful eruptions on the planet or not.
Planetologists believe that the traces of powerful volcanic eruptions near the planet's south pole, as well as potential traces of volcanic emissions in the atmosphere of Venus, discovered in 1978 by the American Pioneer Venus mission, are in favor of their hypothesis.
Lunin and his colleagues hope that their theory can be tested in the coming years, when a new generation of interplanetary probes will be sent to Venus.They will be able to accurately measure the proportion of phosphorus compounds in its atmosphere, as well as discover new traces of volcanic eruptions on the surface of the second planet of the solar system.