Is It Really Worth Going To Venus Again?

 

A recent image of Venus

The yen to send spacecraft to Venus is in many ways totally understandable.  This planet is a near twin of Earth,  comparable in size, mass and composition, and it is also the planet whose orbit is the closest to Earth’s. 

But let's be clear that the history of the two planets diverged. While Earth is moderate in temperature and largely covered with water, Venus, with a dense atmosphere of carbon dioxide, is a hellishly hot 900 degrees Fahrenheit at the surface. After numerous missions by the United States and the Soviet Union to explore it in the 1970s, ’80s and ’90s, attention has shifted elsewhere.  Why keep visiting a cosmic hellhole expecting anything but... well, hell!  

Who knows?  But now two new planned Venusian missions (DAVINCI+ and VERITAS)  have workers at Lockheed Martin in Jefferson County, Colorado ecstatic given they will be building the craft.   What's changed?  Venus reentered the planetary limelight after a team of scientists using Earth-based telescopes claimed in a paper appearing in  Nature Astronomy  that they had discovered "compelling evidence for microbes"  living in the clouds of Venus -  where temperatures remain comfortably warm instead of scorching.   

They also claimed the  discovery of phosphine gas  -  based on a molecule, phosphine, for which they could come up with no plausible explanation for how it might have formed there except as the waste product of living organisms. According to one of the team's lead authors, Sara Seager, interviewed by CNN at the time:

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

DAVINCI+ could confirm conclusively the presence of phosphine. After entering orbit, the spacecraft would drop a spherical probe full of instruments that would sniff and analyze gases as it descended through the atmosphere for just over an hour.  Seriously?  Well, that's the idea.  

VERITAS, meanwhile,  will send an orbiter that would produce high-resolution three-dimensional global maps using radar, and a spectrometer will identify what the surface is made of. It also will measure variations in the planet’s gravitational pull, which will offer clues to its interior geological processes .  Akatsuki, from the Japanese space agency, is the only spacecraft currently at Venus.  Let us note the craft actually failed to attain Venusian orbit in December, 2010.  It then orbited the Sun for 5 years,  after which engineers managed to place it into an alternative elliptical orbit by Dec. 7, 2015.  It has been in this alter orbit ever since - studying the stratification of the Venusian atmosphere and the planet's cloud physics.

But are these two new Venus robot missions really needed, to try to find signs of life?  Let's note the Nature Astronomy paper's lead author admitted that all the hopes are pinned to its occurrence in one thin "sweet spot" in the atmosphere, 48 to 60 km above the surface.  That is a mighty thin envelope on which to place a  bet for 100 million bucks. Recall here my post,

• The Scientific Meaning Of Impossibility Statements

And specifically where  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

Now,  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 lead author 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. 15, 2020  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  are we really going to make a $100 million bet on a "whiff" of cordite? Evidently so, and I am for it if it means the question can be settled once and for all, i.e. that Venus is a lifeless hellhole - without even any cloud - based, temperate  "sweet spots" to hold microbes.

Sheesh, the improbable stretches some scientists will make to get published!