If you want to know why they went looking for phosphine then watching this episode of the Sky at Night gives the detailed story as told by those who found it.
https://www.bbc.co.uk/programmes/b00...pisodes/player
Mark
Member
If you want to know why they went looking for phosphine then watching this episode of the Sky at Night gives the detailed story as told by those who found it.
https://www.bbc.co.uk/programmes/b00...pisodes/player
Mark
Established Member
A hypothesis paper published a couple of years ago about what sort of microbes might conceivably flourish in the cloud banks of Venus.
Mentions several known Earth species as analogs to hypothesised Venus life, for instance the Earth species Acidithiobacillus ferrooxidans. This organism can function in anaerobic conditions. It likes high acidity, sulphur compounds and iron, which is available in Venus clouds in the form of dust particles from the surface. The species actually produces sulphuric acid. It does this by oxidising other sulphur-containing substances, while reducing iron compounds from ferric to ferrous...
Order of Kilopi
What we may well have here, is a classic example of how the terms 'plausible' and 'implausible', when inferred from our local and past experiences, may just not be adequate for inferring the existence of something as complex as life, from remote planetary observations.
Logical inferences drawn from remotely sensed data, in this topic, just aren't considered adequate for eliminating the unknowns (and that's in spite of any Earthly lab experiment test data at hand).
As an example one can cite the example of the mysterious element Nebulium:
As Helium was successfully discovered first as a spectral line in the Sun's chromosphere before its discovery on Earth, remote spectral line sensing was subsequently considered as being a standard way of detecting existence beyond Earth.
However, remote sensing can also lead to incorrect conclusions:
The OIII spectral line in emission nebulae, was wrongly attributed to an unknown element, which was named 'Nebulium', in the 19th century. Nebulium turned out to be a quantum mechanical "forbidden" transition of the doubly ionized oxygen atom O²⁺ which can only exist in the extreme vacuum of outer space, due to low collision rates between atoms.
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A couple of quotes from Clara Sousa-Silva. She’s a member of team that reported this discovery, and she's also the author of an earlier paper about PH3 as a biosignature.
“As crazy as it might sound, our most plausible explanation is life” (The Atlantic)
“What we need now is for the scientific community to come and tear this work to shreds. As a scientist, I want to know where I went wrong.” (Los Angeles Times)
Order of Kilopi
... there's that word 'plausible' again ...Originally Posted by Colin Robinson
Simple .. give up believing what's 'plausible' .. because that ain't science.
Established Member
I have a feeling this is going to go the way ALH 84001 went. It's likely to be a long time before we can scoop up some Venusian atmosphere and and take a look. Like Viking, probably will be inconclusive.
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Interesting bit of history.
Karl Popper's phrase "conjectures and refutations" comes to mind. As Popper understood, scientists have often put forward hypotheses which were later shown to be wrong, because new data was found and/or because someone came up with another hypothesis which explained all available data more convincingly.
So did Popper think scientists should avoid putting forward any hypothesis? No. Because whether a hypothesis tests out well (e.g. the Helium hypothesis), or whether it tests out badly (e.g. the Nebulium hypothesis), either way it gives scientists something to test.
Clara Sousa-Silva hasn't said anything about believing. In this context, "plausible" means worth more testing.
Last edited by Colin Robinson; 2020-Sep-17 at 08:44 PM.
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The case of ALH 84001 was about features which some researchers interpreted as fossils of ancient micro-organisms. The process of fossilisation replaces most of the substance of an organism but conserves its shape. The problem is that it's difficult to prove whether something is a micro-organism or simply a micro mineral formation on the basis of shape alone.
The reported phosphine is a different matter. Considering how quickly this substance breaks down, it wasn't produced millions of years ago, it is being produced today...
I don't think it will be a long time. It's true that the Venera missions to Venus' surface expired after a hour or two, but the Vega 1 and Vega 2 balloon missions of 1985 both survived for about 48 hours because they didn't have to cope with intense heat.It's likely to be a long time before we can scoop up some Venusian atmosphere and and take a look.
How much work could a balloon probe with 2020s technology do in 48 hours?
That was then. This is now.Like Viking, probably will be inconclusive.
Moderator
Full stop!
We're not turning this into another philosophy or linguistics thread. If you want to have such a discussion, start a new thread on it in Science & Technology. This thread will stick strictly on the finding from Venus.
Established Member
I just read in the comments section of a different news sight a guy claiming phosphine had discovered in the atmosphere of Jupiter. I've never heard that before. If it had been, we'd have been discussing life there a long time ago.
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It's true that phosphine has been discovered in the atmosphere of Jupiter — if you google words like "phosphine, Jupiter" you'll find lots of good references. But Jupiter and Venus are chemically very different, in such a way that Venus' phosphine is a surprise while Jupiter's phosphine wasn't and isn't.
The difference is, Venus' atmosphere is an oxidising environment (i.e. rich in oxygen compounds like CO2) whereas Jupiter's is a reducing environment (i.e. rich in hydrogen and compounds of hydrogen). In an oxidising environment, you'd expect to find phosphorus in oxidised forms, such as phosphates (compounds of PO4) but not in reduced forms like phosphine (PH3). In a reducing environment, it's the other way around...
Last edited by Colin Robinson; 2020-Sep-18 at 12:03 AM.
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Thank you, you just strengthened my argument on that other site. I had googled jupiter atmosphere and found nothing on phosphine.
Order of Kilopi
Earth's extremophiles such as Bacillus subtilis, typically go into a dormant state when exposed acidic environments, in order to survive.
During this dormant phase, the bacteria develops a protective endospore.
This Venusian lifeform however, is completely different because it somehow remains biochemically active, whilst in a sulfuric acid environment.
Concentrated sulfuric acid is a powerful dehydrating agent which destroys earthly organic matter.
The question is: How do these Venusian organisms survive, whilst remaining biochemically active?
Order of Kilopi
You're jumping a bit ahead there. We don't yet know if there are in fact organisms, or if there is some process going on that we don't understand.
As above, so below
Order of Kilopi
I'm not jumping ahead .. I'm speaking about Seager etal's hypothetical model of the Venusian lifeform/lifecycle. Her team published an extensive paper/article in Astrobiology, as part of the Greaves/Seager etal announcement paper of the detection of the atmospheric phosphine. (See the supplementary info in the references section of the announcement paper).
Ie: there's a lot more information behind this than just the announcement paper.
Order of Kilopi
Water's hard to get away from here, and acidity is generally weaker and less common than on Venus. Any exposure to concentrated sulfuric acid is normally local and temporary on Earth. There's been no strong driver to adapt to a condition that is transitory.
Hypothetical Venusian microbes would have had a different set of conditions, a very different chemical environment from the start, and a whole world of evolving experiments adapting slowly to universal changes. That's assuming they shared a commonality with our life and had an innate vulnerability to sulfuric acid in the first place, which is not a given.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
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How do you square your statement that typical earth extremophiles enter a dormant state, with Colin Robinsons post which has the Acidithiobacillus ferrooxidans remaining active and actually producing H2SO4?
Surely a lifeform that produces an acid opens the way for one that can live in an acidic environment?
Order of Kilopi
Whether the phosphine is biogenic or the product of different chemistry, the answer is the same: more research, more exploration of Venus.
"I'm planning to live forever. So far, that's working perfectly." Steven Wright
Order of Kilopi
On Earth there's a lot more water. Venus' atmospheric H2SO4 is a lot more concentrated. The proposed hypothetical Venusian microbes are supposed to germinate, (metabolize and divide), in a mostly H2SO4 suspended droplet, above the 33-48 kms altitude layer. They have to be sporulated at that layer in order to preserve themselves, awaiting gravity waves to elevate them again to the higher and cooler altitudes.
Order of Kilopi
Water is hypothesised as having been an intrinsic essential factor in the formation of our pre- and post-biotic life.
There is no evidenced basis for assuming lifeforms which aren't vulnerable to sulphuric acid's dehydrating effects.
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Yes. I don't think there is any Earth organism which would thrive at Venus-level acidity. But there are a range of Earth organisms which thrive at levels of acidity that are seriously harmful to other Earth organism. The WP page Acidophile mentions some of them, and gives information about how they do it.
Some have ways of keeping their cytoplasm neutral (in the acid/base sense) in spite of being surrounding by acidity. Others have acidic cytoplasm, and special proteins that contain lots of fragments of acid molecules. Apparently it is easily to live in an acidic solution if you are acidic yourself.
It's possible that the original environments of Earth life and Venus life (if it exists) were not very different. Four billion years ago, Earth had a lot more carbon dioxide and much less free oxygen than today, and Venus probably had more water than today and hence lower acidity. While Earth life adapted to increasing levels of O2, Venus life adapted to increasing concentrations of H2SO4.Hypothetical Venusian microbes would have had a different set of conditions, a very different chemical environment from the start, and a whole world of evolving experiments adapting slowly to universal changes. That's assuming they shared a commonality with our life and had an innate vulnerability to sulfuric acid in the first place, which is not a given.
Last edited by Colin Robinson; 2020-Sep-18 at 10:41 PM.
Order of Kilopi
This is not the hypothesis proposed as part of the OP announcement of atmospheric phosphine.It's possible that the original environments of Earth life and Venus life (if it exists) were not very different. Four billion years ago, Earth had a lot more carbon dioxide and much less free oxygen than today, and Venus probably had more water than today and hence lower acidity. While Earth life adapted to increasing levels of O2, Venus life adapted to increasing concentrations of H2SO4.
Order of Kilopi
In the 45-75km altitude range of Venus, the H₂SO₄ concentration is 73-98%.
H₂SO₄ is produced in the Venusian atmosphere as described by the following reactions:
CO₂ → CO + O (photo-disassociation of CO₂ by photons.)
SO₂ + O → SO₃
2SO₃ + 4H₂O → 2H₂SO₄. H₂O
H₂SO₄ is hygroscopic and its concentration is a function of the amount of H₂O absorbed.
Even at 70% concentration, H₂SO₄ is highly corrosive to most known organic matter, so rather than reactivating the hypothesised Venusian bacterium inside the spore, it is more likely to destroy it.
Established Member
Have you read the researchers’ paper in the journal Astrobiology?
There’s a section called “Supplementary Information”. On page 16 of that section, they mention:
“Computer models of Venus90,91 have shown that a habitable surface with liquid water could have persisted up to 715 million years ago”…
How does that differ from what I've said about ancient conditions on Venus?
Order of Kilopi
The Seager/Greaves (etal's) hypothesis is not dependent on biochemical properties speculated as being specific to Venusian only originating lifeforms, in order to overcome destruction by concentrated atmospheric acid, during germination.
Established Member
Yes the concentrated H₂SO₄ probably would destroy the Venusian microorganism…
IF Venusian microorganisms today were chemically just like Earth ones.
Which is why they wouldn’t be…
Established Member
You're referring to this paper? Seager and Greaves make the point that because of the sulfuric acid concentration, current Venusian biota would have to differ substantially in their chemical composition from Earth biota. (Unless they were protected from the acidity by some sort of shell, which Seager and Greaves don't think would work.)
I accept their arguments regarding all these points.
They don't specify what chemical compounds the biota would be composed of, however it's apparent from their section about nutrients that they are thinking in terms of compounds of CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur) as on Earth. These would be exotic CHNOPS compounds from our point of view.
I don't think their position is in conflict with the idea that Earth life and Venus life may have been more chemically similar in the past, when Venus had more water than it has today, and Earth had more carbon dioxide and less O2 than today.
Last edited by Colin Robinson; 2020-Sep-19 at 05:03 AM.
Order of Kilopi
So, if sugars, nucleic acids, RNA, DNA, proteins, lipids and complex carbohydrates are completely off the menu, then exactly what bio-chemically active 'organics' are left to perform hypothetical metabolism, division and excretion of atmospheric phosphine?
With that above quoted statement, any meaning the term 'Venus life/microbes' may have barely hypothetically ever had, was completely destroyed by concentrated sulphuric acid. Apart from being a powerful dehydrating agent, the reaction with water is highly exothermic. The mechanism of destruction would be the heat generated in the hydration reaction, which would simply boil any Venusian 'cytoplasm' functional equivalent .. and completely destroy it.
The most likely solution to this dilemma is that the atmospheric phosphine is being produced by an as yet, unknown atmospheric/geochemical process which is not life.
Established Member
I'd suggest the CHNOPS compounds in Venus microbes are likely to be chemically akin to the liquid medium in which they operate.
They'll contain chemical units like the "acid residues" found in the biomolecules of some Earth organisms that thrive in comparatively acidic environments.
But in the Venus organisms, chemical units of this sort will be much more prevalent.
This means the organisms will contain lots of sulfur atoms attached to oxygen atoms, as the sulfur atom in a sulfuric acid molecule is attached to oxygens.
What if the liquid in Venus cells is similar in composition to the liquid in Venus cloud droplets, i.e. predominantly H2SO4?With that above quoted statement, any meaning the term 'Venus life/microbes' may have barely hypothetically ever had, was completely destroyed by concentrated sulphuric acid. Apart from being a powerful dehydrating agent, the reaction with water is highly exothermic. The mechanism of destruction would be the heat generated in the hydration reaction, which would simply boil any Venusian 'cytoplasm' functional equivalent .. and completely destroy it.
Does concentrated sulfuric acid react exothermically with itself?
You asked me what sorts of substances might be involved in Venus biochemistry, and I've made an effort to answer.The most likely solution to this dilemma is that the atmospheric phosphine is being produced by an as yet, unknown atmospheric/geochemical process which is not life.
Now please tell me, what sort of substances do you think might play a part in your hypothesised atmospheric/geochemical processes?
Established Member
Some others also consider asteroid grazing as a mechanism for transfer.
Transfer of Life Between Earth and Venus with Planet-Grazing Asteroids
https://arxiv.org/abs/2009.09512
As the kind of Earth bacteria prefer an anoxic environment, one might think that a Melolsh type impact of a marsh might be the transport method. But sending an earth rock into space to Venus would involve sudden large impact heat and shock to unprotected bacteria that did not have time to form an endospore. If the marsh was facing a dry spell, then the threat of dessication would drive the bacteria to form a resistant endospore that could survive being blown to the upper atmosphere.
Endospore
https://en.wikipedia.org/wiki/Endospore
Note that endospores need excess sulfur which is present in clouds of Venus as sulfuric acid.
Lingam and Loeb also recently posted a paper:
On The Biomass Required To Produce Phosphine Detected In The Cloud Decks Of Venus
https://arxiv.org/abs/2009.07835
They make a number of assumptions and caution their results are preliminary.
One is that the microbes are constrained to live within aerosol droplets. Threats are too low pH, dessication of water, colony overgrowth, the need to seek out another colony for genetic diversification. Forming endospores to travel between droplets may be essential for survival, Whether the metabolite phosphine is a byproduct of endospore formation or reactivation after arrival to a new droplet remains to be demonstrated.
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