Thursday, February 4, 2021

Life on Venus? Phosphine Claim Challenged

Environmental & Science Education, STEM, Cosmology, Solar System, Astrophysics, Nature of Science

Ed Hessler

We knew this was coming--a challenge/challenges to the life on Venus claim that because it's atmosphere might contain phosphine gas, a potential sign of life. This claim was first reported last September and I posted a note about the original study. Phosphine is a relatively simple molecule: one phosphorous atom plus three hydrogen atoms. It can come from both biological sources and non-biological sources which presents a problem at the outset.

In reporting for the scientific journal Nature, Alexandra Witze discusses the details based on papers that have been accepted for publication in Astrophysical Letters. They were  posted on a preprint server on January 26.

Witze writes "The latest papers pretty clearly show that there is no sign of the gas, says Ignas Snellen, an astronomer at the University of Leiden in the Netherlands who has published a different critique of the phosphine claim. 'This makes the whole debate about phosphine, and possibly life in the atmosphere of Venus, quite irrelevant.'”

"Jane Greaves, an astronomer at the University of Cardiff, UK, who led the team that made the original phosphine claim, says she and her colleagues are still reading through the new papers and will comment after they’ve evaluated them."

The new studies are based on reprocessed telescopic data and on "modelling the structure of Venus's atmosphere at various altitudes." The modelling studies found that there is a better explanation, "the presence of sulfur dioxide more than 80 kilometers above the planet's surface--not by phosphine above the surface," as originally claimed.

The new studies have not completely debunked the original claim and the case will not be completely closed until new observations are made of Venus. These are planned, some months away and others years away.

This is how science works--is there an alternative and better explanation supported by evidence? The late Carl Sagan stated in what has become a popular phrase, “Extraordinary claims require extraordinary evidence”. Sagan reworded Laplace's principle, which says that “the weight of evidence for an extraordinary claim must be proportioned to its strangeness”. This statement is at the heart of the scientific method, and a model for critical thinking, rational thought and skepticism everywhere."

This is easy to say in a flippant way as though everything was obvious. In a trenchant review of this concept, Patrizio E. Tressoldi reviews some of the problems about such claims and what constitutes such evidence. He limits the discussion to quantitative psychology. The paper is demanding. I think the physical claim and data are much more amenable to the the idea of a scientific claim rather than thinking of it as an extraordinary claim. The answer is evidence and the papers referenced above are a start. More is coming.

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