Scientists have astonished the world last yearear by claiming to have discovered it traces of phosphine in the Venusian clouds. New research suggests this gas – which is exciting, is produced by microbes– was not actually responsible for the signal they discovered. Instead, it was likely sulfur dioxide, a not-so-exciting chemical.
Out of the ordinary Research published in Nature last September is challenged by a paper to be published in The Astrophysical Journal, a preprint of which is currently available on the arXiv. This is not the first article to be used criticism the apparent discovery of phosphine on Venus, and it probably won’t be the last.
That phosphine could be present on Venus was a revelation that surprised us, and that’s because living organisms are one of the few known sources of the smelly gas. The team responsible for the apparent discovery, led by astronomer Jane Greaves of Cardiff University, found the evidence in spectral signals collected by two radio dishes: the James Clerk Maxwell Telescope (JCMT) and the Atacama Large Millimeter / submillimeter Array (ALMA) . Spectral lines at certain wavelengths indicate the presence of specific chemicals, and in this case they implied the presence of phosphine in the Venusian cloud layer.
The authors of the Nature study did not claim that life exists on Venus. Instead, they asked the scientific community to explain their rather bizarre observation. Indeed, it was an exceptional claim, as it implied that Venus – one of the most inhospitable planets in the solar system – might be habitable, with microscopic organisms floating through the clouds.
Unfortunately, this does not seem to be the case.
“Instead of phosphine in the clouds of Venus, the data is consistent with an alternative hypothesis: they detected sulfur dioxide,” said Victoria Meadows, a co-author of the new study and a professor of astronomy at the University of Washington, in a statement. statement. “Sulfur dioxide is the third most abundant chemical in Venus’ atmosphere and is not considered a sign of life.”
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Meadows, along with researchers from NASA, the Georgia Institute of Technology and the University of California, Riverside, came to this conclusion by modeling the conditions in the Venusian atmosphere, which they did to recreate the radio data collected by the original team. to interpret.
“This is what is known as a radiation transfer model and it contains data from decades of observations of Venus from multiple sources, including observatories here on Earth and space missions such as Venus Express,” explains Andrew Lincowski, a researcher with the UW Department of Astronomy and the lead author of the article, in the statement.
Equipped with the model, the researchers simulated spectral lines produced by phosphine and sulfur at multiple atmospheric heights on Venus, as well as how those signatures were received by ALMA and JCMT. The results showed that the shape of the signal, detected at 266.94 gigahertz, likely came from the mesosphere of Venus – an extreme altitude where sulfur dioxide can occur but phosphine is not because of the harsh conditions there, research shows. In fact, this environment is so extreme that phosphine doesn’t last more than a few seconds.
As the authors claim, the original researchers underestimated the amount of sulfur dioxide in Venus’ atmosphere and instead attributed the 266.94 gigahertz signal to phosphine (both phosphine and sulfur dioxide absorb radio waves around this frequency). This happened, according to the researchers, as a result of an “unwanted side effect” known as spectral line dilution, study co-author and NASA JPL scientist Alex Akins said in the statement.
They concluded low detection of sulfur dioxide because of [an] artificially weak signal from ALMA, ”added Lincowski. “But our models suggest that the line-diluted ALMA data would still have been consistent with typical or even large amounts of sulfur dioxide from Venus, which could fully explain the observed JCMT signal.”
This new result could be devastating to the Nature paper, and it will be interesting to hear how the authors respond to this latest criticism. That said, some scientists believe the writing is already on the wall, or rather, the trash can.
“Soon after the publication of the original work, we and others expressed strong doubts about their analysis,” writes Ignas Snellen, professor at Leiden University, in an email. “Now I personally think this is the last nail in the coffin of the phosphine hypothesis. Of course, one can never prove that Venus is completely phosphine-free, but at least there is now no evidence to suggest otherwise. I’m sure others will keep looking. “
In December, Snellen and his colleagues contested the Nature study, arguing that the method used by the Greaves team resulted in a “spurious” high signal-to-noise ratio and that there is “no statistical evidence” for phosphine on Venus.
The apparent absence of phosphine on Venus, and thus the absence of any hints of microbial life, is much less interesting than the opposite, but that’s the way it is sometimes. Science makes no statements or promises about the interestingness of all things, and we, as defenders of the scientific method, must come to accept our unfolding universe as we find it.