Life - Even Microbial - Exists In The Clouds Of Venus? Highly Unlikely

 
Upper atmosphere of Venus from ESA "Venus Express" spacecraft

A few days earlier, leaving much controversy in its wake, a paper appeared in  Nature Astronomy   on the  discovery of phosphine gas  in Venus' atmosphere, suggesting the possibility of life - well, at least in its clouds. (The surface, hot enough to melt lead, would not be any realistic place you'd expect life).    As explained below by one of the Nature paper's lead authors (Sara Seager),  in a CNN op-ed: 'Our crazy finding suggesting life on Venus' (opinion) - CNN

https://www.cnn.com/2020/09/14/opinions/crazy-finding-life-on-venus-seager/index.html

"The finding is so astonishing because phosphine should not be present in Venus' atmosphere. Phosphine needs lots of hydrogen and the right temperatures and pressures to form -- conditions found on Jupiter and Saturn but not at all on Venus. My team at MIT exhaustively searched all known chemistry and did not find any way for phosphine gas to be easily produced on Venus. Planetary processes including volcanoes, lightning, meteorites entering Venus' atmosphere are also "no gos" in that some might produce the tiniest amount of phosphine but not nearly enough to match the observations."

But she does concede this need not imply existence of alien life, i.e.

"Does this mean Venus has alien life in its atmosphere producing phosphine gas? Not necessarily.  Venus is a very hostile place for any kind of life as we know it. The surface is scorchingly hot -- far too hot for complex molecules needed to make up life. High above the surface, the atmosphere becomes colder and colder. On Venus there is a sweet spot at 48 to 60 km (30 to 37 miles) above Venus' surface, in the clouds, where the temperature is not too hot, not too cold, but just right for life."

Does this mean Venusian microbial life can exist in that "sweet spot?  Well, yes it is "possible".  See my previous post:

• The Scientific Meaning Of Impossibility Statements

Wherein I note:

"in science, the applicable terms that usually replace "impossibility" are what we call "laws of permission" and "laws of denial". The first detail all the actions that are allowed based on the laws of physics; the latter detail all the actions disallowed.

The laws of denial are predicated on such foundational physical laws as: the laws of conservation of mass-energy, momentum and electric charge. "

In the case of Venus, the laws of denial begin to enter when one purports to  posit any kind of life on a planet with temperatures  hot enough to melt lead as well as concentrations of sulfuric acid that rival anything on Earth - even in labs.  A first emergence of at least improbability - if not impossibility- arrived when Seager writes in her CNN op-ed piece:

"The acid environment is billions of times more acidic than the most acidic environments on Earth. Earth-life components including DNA, proteins, and amino acids would be instantly destroyed in sulfuric acid. Any life in the Venusian clouds would have to be made up of building blocks different than Earth life, or be protected inside a shell made up of sulfuric acid-resistant material such as wax, graphite, sulfur, or something else."

The immediate problem for me is that her hypothesis, as creative as it is, violates the Ockham's Razor principle.  Also known as the principle of parsimony, i.e.  the simplest of competing hypotheses is the most likely to be correct. In this case having to hypothesize a special "sulfuric acid  resistant covering" for an organism to withstand an acidic environment "billions of times more acidic than the most acidic environments on Earth."

 Even one of the study's co-authors - David Clements- an Imperial College of London astrophysicist (quoted in a Sept. 15th  AP article appearing in The Denver Post) admitted the conclusion is nowhere near final:

"It's not a smoking gun.  It's not even a gunshot residue appearing on the hands of your prime suspect. But there is kind of a whiff of cordite in the air."

Well, maybe, maybe not.  But what exactly would a simpler hypothesis be, say that wouldn't require microbial life that would need a shell of sulfuric acid resistant material?  The answer is volcanoes, such as found by the European Agency's "Venus Express" spacecraft 4 years ago.  Not any old explosive volcanoes (like Mt. Saint Helens), but rather more like "slow, oozing effusions"  that'd be capable of continuously and slowly pumping out not only CO2, SO2 but phosphine as well.  In this case, the effusive nature spread over vast 'hot spots" could spout immense quantities of these gases that would otherwise need hundreds of separate explosive volcanoes.  

 Of course, the volcano hypothesis is disputed by both authors.  Seager insists that "not a single process we looked at could explain phosphine levels as high as in our findings".  But let's bear in mind these "findings" are really data tied to a particular model which may not be representative or accurate at all, especially if the volcanoes we're talking about are the continuous "oozing" kind discovered by the ESA craft. 

 As Cornell University astronomer  Lisa Kaltenegger observes, "we don't know enough about Venus to say that life is the only explanation for the phosphine."  Planetary geochemist Justin Filiberto -  at the Lunar and Planetary Insittute in Houston- mostly concurs, noting in the same AP piece: "the levels of phosphine found might be explained away by volcanoes."   Adding that recent studies were not taken into account which disclosed "Venus may have far more active volcanoes then originally thought."

Clements, however, disagrees, saying that this would make sense "only if Venus is 200 times more volcanically active as Earth."   But if the volcanoes were of the effusive variety found by the ESA  such a humongous ratcheting up would not be needed.

In the end, it seems to me the matter cannot be solved by arguing over models from tens of millions of miles away. We need to send more spacecraft to Venus to unlock the phosphine and other secrets.   Fortuitously, NASA is considering two possible Venus missions in the near future. One of them (DAVINCI+) would traverse the Venusian atmosphere as early as 2026.

So like it or not, we may have to wait at least 5-6 more years to finally solve the phosphine riddle - if it is solvable at all.