A study suggests that the possible phosphine discovered in the atmosphere of Venus was probably just ordinary sulfur dioxide. So "the greatest scientific discovery in all of history" will have to wait.
In mid-September, a team announced that it had detected phosphine in the upper atmosphere of Venus. The announcement made headlines. And for good reason, on our planet, we know that these molecules can be produced by anaerobic bacteria. Since this announcement, other studies have questioned the reliability of this possible detection. One, led by the University of Washington in conjunction with NASA researchers, now concludes that the alleged phosphine…wasn’t.
Each chemical compound absorbs unique wavelengths of the electromagnetic spectrum. Astronomers then analyze them to learn more about the chemical composition of an atmosphere, for example. As part of its study, the first team announced the detection of a spectral signal of 266.94 gigahertz in the Venusian atmosphere .
You should then know that phosphine and sulfur dioxide, another compound much more likely to exist on Venus, absorb radio waves near this frequency, hence the interrogation of researchers.
To differentiate between the two compounds, the team had made follow-up observations with the Atacama Large Millimeter/submillimeter Array, or ALMA. Analyzes of ALMA observations at frequencies corresponding only to sulfur dioxide then led the team to conclude that sulphur dioxide levels on Venus were too low to account for the detected signal . As a result, it must have come from the phosphine instead.
As part of this new study, the researchers began by modeling conditions in Venus' atmosphere based on decades of observations. They then used this foundation to comprehensively interpret observed and unobserved characteristics in ALMA's datasets.
The team used this model to simulate phosphine and sulfur dioxide signals at different levels in Venus' atmosphere and analyze how these signals would be picked up by ALMA in their configurations. Based on the shape of the signal, the researchers first pointed out that the absorption was not coming from Venus' cloud layer as reported by the first team.
Instead, the signal observed came from the mesosphere of Venus, located 80 km above the surface . However, at this altitude, the harsh chemicals and ultraviolet radiation would destroy the phosphine molecules in seconds according to the researchers.
They also found that the ALMA data had significantly underestimated the amount of sulfur dioxide in Venus' atmosphere . "ALMA's antenna configuration at the time of the 2019 observations had an undesirable side effect:signals from gases found almost everywhere in Venus' atmosphere, such as sulfur dioxide , emit weaker signals than gases distributed on a smaller scale “, underlines Alex Akins, of NASA’s JPL. This phenomenon is known as spectral line dilution.
In conclusion, the authors note that sulfur dioxide may not only explain the observations made initially, but that these results are also more consistent with what astronomers know about the atmosphere. of the planet which includes clouds of sulfuric acid. Finally, remember that sulfur dioxide, which is the third most common chemical compound in the Venusian atmosphere, is not considered a sign of life .
