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article imageIf something’s alive on Venus, where is it? Substrate, maybe?

By Paul Wallis     Sep 14, 2020 in Science
Sydney - The recent discovery of an organic compound called phosphine has raised a huge storm of interest. Venus is supposed to be dead. It’s looking like it isn’t. The questions are rising fast.
The discovery by researchers at the James Clerk Maxwell Telescope in Hawaii is pretty much out of any known ballpark on Venus. Phosphine contains one phosphorous atom and 3 hydrogen atoms. These elements aren’t high profile on Venus, which is full of active sulphur dioxide and incredibly hot. The atmosphere is mainly carbon dioxide with nitrogen.
You’ll note – Not much mention of hydrogen at all in this description. On Earth, hydrogen is tied up in many other compounds, like water. It’s hard to tell where the hydrogen on Venus might be. It must be there, but where? As for phosphorous on Venus, it’s not even a topic for discussion, apparently.
(It’d be nice, and efficient, if somebody would simply put all the figures for basic Periodic Table elements in planetary atmosphere and surface descriptions. Doing it this way, we have to actually ask where the phosphorous comes from in either the atmosphere or surface, or sub-surface.)
What’s so fascinating about phosphine? A lot.
Phosphine can be produced by organic or inorganic chemical processes. The finding of phosphine of itself isn’t proof of life on Venus, because other processes can’t yet be excluded.
• The mere presence of phosphine, however, is a checklist of questions:
• Where’s the phosphorous on Venus? You don’t get phosphorous in anything, anywhere, unless there’s a local source.
• How does phosphine get into the atmosphere?
• Are there any other forms of phosphorous on Venus? (If so, like phosphine, they’d be a clue to other processes on the planet.)
• What can generate enough phosphine to be recognizable on Earth? You’d need a fairly large process to push enough to be recognizable into the furious Venusian atmosphere.
• The organic processes which produce phosphine in anaerobic conditions aren’t well documented. There are reasons to believe it’s the result of microbial action, but not well defined.
Microbial life on Venus isn’t so unlikely
Given that there are organic materials covering the entire visible universe, life showing up elsewhere is inevitable. On Venus, however, the conditions for life of any kind are qualified by a fantastic array of violent chemical actions.
Heat and sulphur adapted microbes on Earth are well-known. No problem there. The Venusian atmosphere and volcanoes aren’t so unlike Earth, just much more dynamic.
However – A glitch applies to atmospheric microbes on Venus. If these organisms were widespread in the Venusian atmosphere, you’d expect to see a lot of traces. In this case, there’s only one trace, phosphine, with no atmospheric source identified. So maybe not atmospheric microbes.
There’s another possibility – Sub-surface microbes, occasionally venting phosphine through the upper surface. Venus may be in a different, hot, version of Snowball Earth, in which terrestrial microbes were living under the prevailing environmental conditions. Traces of organic activity would have shown in the atmosphere as gaps in the surface released CO2, etc.
On Earth, microbes are known to exist in very strange places. Deep under the ocean floor, and in the Earth’s crust, for example. Billions of tons of microbes, according to some reports. That’s not at all unlikely, given the billions of years of sedimentation and “burying” of ancient microbial communities which have managed to live on regardless of those conditions.
The logic of substrate microorganisms on Venus isn’t hard. Venus and Earth formed at roughly the same times, with various local cataclysms dictating how they evolved. It’s unlikely there would be no phosphorous on Venus. Rocky planets tend to contain quite a mixed bag of elements. The only real issue is where is this phosphorous on Venus? It couldn’t exist as a single element on its own, because it’s a “hyperactive” element. It oxidizes and combines readily with many elements. Even in an anerobic environment, it’s highly combinative.
So the substrate is a good working option. The original phosphorous could be accessed by microbes in the substrate, and almost nowhere else. The clue is the nitrogen on Venus. Microbes can use nitrogen to access phosphorus under anerobic or anoxic conditions.
Bingo? Not quite yet.
The phosphine theory stands up, but it needs proof. It also needs an evaluation of a whole spectrum of possible processes for producing phosphine. If substrate bacteria are at work, there must be a large enough population of them to generate those traces, using some pretty spectacular chemistry.
This could be very handy chemistry for the future, using microbes to source elements like phosphorous and other “touchy” things. Expect some very important oohing and aahing as this problem is explored.
More about Venus phosphine, substrate bacteria on Venus, organic generation of phosphine, sources of phosphorous on Venus, anerobic generation of phosphine
 
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