Biological Agent Phosphine Found on Venus

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The astronomers, who reported the finding on Monday in a pair of papers, have not collected specimens of Venusian microbes, nor have they snapped any pictures of them. But with powerful telescopes, they have detected a chemical — phosphine — in the thick Venus atmosphere. After much analysis, the scientists assert that something now alive is the only explanation for the chemical’s source.
Paper
https://www.nature.com/articles/s41550-020-1174-4
 
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That's seems to be to be at least a moderate confirmation of one or more of Fred Hoyle's speculations.

Quote
 
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After much analysis, the scientists assert that something now alive is the only explanation for the chemical’s source.
I don't know where that quote comes from but it's not true. The nature paper explicitly writes
PH3 could originate from unknown photochemistry or geochemistry
@Greg Bernhardt: I think this fits better in the astrophysics section.
 
  • #6
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We usually think of Venus as inhospitable due to its surface conditions- high temperature and atmospheric pressure, and the chemistry of the atmosphere. Generally no thought is given to the possibility of life in its atmosphere.

The clouds at an altitude of ~60km are more temperate, with temperatures up to ~30 °C, and with pressures up to ~0.5 bar.

A group has reported the probable detection of phosphine in this region and considers it a possible biomarker as there is no known physical process should be able to produce or deposit phosphine in the atmosphere.

The paper at Nature- Phosphine gas in the cloud decks of Venus

Also this more accessible version -
Has evidence of life been found in the clouds of Venus?
 
  • #7
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That's seems to be to be at least a moderate confirmation of one or more of Fred Hoyle's speculations.

Quote
Which one of his rather mad speculations do you think this supports?
 
  • #8
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Which one of his rather mad speculations do you think this supports?
hmm − which of his speculations do you think is "rather mad"? I think that some of them are − in his "Evolution From Space" book (which my girlfriend (in 1988) shook her head at me for reading) he articulated the notion that there might be a level of space-alien-person out there who could manipulate the bonding constants − I think that finding phosphine elsewhere than on Earth is a weakly confirming instance supportive of the speculation, not explicitly stated in this form by Hoyle but in my view implicit in some of what he wrote, that some chemicals found on Earth commonly as a result of life processes may not have had to have been originated on Earth ##\dots##
 
  • #11
Ygggdrasil
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It could take a while to figure out the exact source of the phosphine on Venus, and whether that source is likely to be geophysical or biological in nature. Remember, researchers have made similar observations of unexplained sources of methane on Mars (e.g. see this PF thread from 2009), which were initially taken as potential signs of life, but researchers are still studying the potential sources of the methane.

My bet would be on some geophysical source of the phosphine (there may be no known geophysical routes to produce phosphine on Venus because geochemists have not had a good reason to study potential routes for phosphine synthesis on Veuns yet). It definitely warrants further study, however.
 
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  • #12
Tom.G
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I don't know where that quote comes from but it's not true. The nature paper explicitly writes
@Greg Bernhardt: I think this fits better in the astrophysics section.
Probably came from a Popular Press reporter that watched the video interview with the Lead Scientist. The question is asked but it takes close listening to decode the answer given. The video interview is at:

Cheers,
Tom
 
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  • #14
Phosphine is present on Saturn and Jupiter, presumably it is produced abiotically there:
https://www.sciencedirect.com/science/article/pii/S0019103509001328
Hi there! Unlike Venus, Saturn and Jupiter are gas giants, and we all know that phosphine is a poisonous gas. Finding it on Venus could be also explained by volcanoes, lightning or meteorites, but unfortunately that's not the case for Venus. The amounts of phosphine found, (20 molecules per billion) cannot be simply explained by some natural events and the only logical and in my opinion correct thought is that it is produced by microbiological life, which might exist in the atmosphere at about 50-70 km above surface, where the conditions like temperature and atmospheric pressure are similar to Earth'. However right now, we can only make predictions until we launch a space probe which will investigate these interesting layers of atmosphere of Venus.
 
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I am unsure as to whether phosphine has been detected. What they have detected is a signal corresponding to the rotational 1 - 0 transition of phosphine. They rejected (according to their paper) a possible transition from SO2 because there is insufficient SO2, it being oxidised to SO3, but phosphine would be far more easily oxidised. The only source of phosphorus in the upper atmosphere would presumably be phosphoric acid, but that tends to condense either with itself to make pyrophosphates or other molecules. The paper states that the greatest phosphine intensity is at the equator, and it more or less fades at the poles. That, to me, is suspiciously like the species giving the signal is formed photochemically (because the intensity of light on a given surface area attenuates) but the authors of the paper say that if the signal came from the upper atmosphere, the lifetime of phosphine should be about 1000 seconds. For the same reason, the life would be longer at the poles. If so, there would have to be a very strong production, and I think we should consider there might be some other photochemically produced species giving this signal. I doubt we know much about the photochemistry of the Venusian atmosphere because it is only in the last few decades we have unravelled that of our own atmosphere. I do not know if we know anything about microwave emissions from high-pressure gases.

As for life, phosphine is made by life on Earth by the enzymatic reduction of phosphate, the necessary hydrogen coming from water. I am sceptical that any enzyme could survive in the atmosphere where there is concentrated sulphuric acid, but if we get above the sulphuric acid, then we would also be above any source of phosphoric acid or phosphate, and we would be in the zone of the active photochemical degradation of phosphine. I suspect there is a lot more to be unravelled in this story. The Nature Astronomy paper itself mentions that from a chemistry point of view it shouldn't be there so there is something we don't understand about this signal.
 
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  • #16
Astronuc
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I heard a comment yesterday about the discovery of phosphine in the atmosphere of Venus.

SAGAL: ". . . they [scientists] announced the discovery of a certain chemical, phosphine, which is only produced on Earth by living organisms. In fact, it's a primary ingredient in penguin poop. So there's only one..." I haven't checked the veracity of the comment, but I'm skeptical. I know that phosphate is mined from seabird guano, so I expect that phosphorus is found in penguin poop, but I can't imagine phosphine being a primary ingredient in poop. It might be that it the poop is a primary source of phosphine on earth.

Peter Sagal is host of NPR's Wait, wait, . . .
 
  • #17
Ygggdrasil
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Peter Sagal is host of NPR's Wait, wait, . . .
Important to note that NPR's Wait, Wait Don't Tell Me is a satirical, comedy game show, and although they discuss the news, they aren't a good source for the news.
 
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  • #18
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One thing to remember is that evolution would not direct a mechanism to make phosphine. Anaerobes reduce carbon compounds to methane as an energy source. Phosphine has been reported in certain marsh gas, but I have wandered around numerous swamps and never smelt it. It is also extremely unlikely to come from anaerobes in the Venusian atmosphere on evolutionary grounds. All life needs phosphate for a variety of reasons. It is the only viable linking agent for nucleic acids (or whatever you need for reproduction. You need two stable linkages to link the units in a polymer, and a third one to bring solubility, otherwise the second law of thermodynamics means your duplex cannot separate. This problem with polymers is why recycling polymer mixtures is so difficult.) It is also the main energy transfer agent (ATP, and it is hard to see how anything but a tripolyphosphate could evolve) and adenosine phosphates are critical solubilizing agents in many enzyme cofactors. Phosphate is going to be very rare in the Venusian atmosphere independent of sulphuric acid (which would tear enzymes apart) so why would it develop the means to waste it? Since there is not much methane (any??) in the Venusian atmosphere, phosphine cannot be an accidental byproduct of methane production.
 
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  • #19
Astronuc
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The existence of phosphine aside, the article states "Here we report the apparent presence of phosphine (PH3) gas in Venus’s atmosphere, where any phosphorus should be in oxidized forms. Atmospheric PH3 at ~20 ppb abundance is inferred. The presence of PH3 is unexplained after exhaustive study of steady-state chemistry and photochemical pathways, . . . "

What would be the source of the phosphorus on Venus, and more particularly, in the atmosphere?

One possible source of P is S via (n,p) or (n,pn') reactions from fast (MeV) neutrons from cosmic ray spallation interactions. That would put the source of P in the upper atmosphere without the need to transport it from the surface. The reaction also produces hydrogen in the vicinity of P.

http://adsabs.harvard.edu/full/1973SSRv...14..663L

http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/cardat.html#c1

How stable would it be in the presence of other molecular species in the atmosphere of Venus?

The atmosphere of Venus is composed of 96.5% carbon dioxide, 3.5% nitrogen, and traces of other gases, most notably sulfur dioxide. . . .
. . . .
The atmosphere contains a range of compounds in small quantities, including some based on hydrogen, such as hydrogen chloride (HCl) and hydrogen fluoride (HF). . . . .
https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Structure_and_composition
 
  • #20
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The reaction also produces hydrogen in the vicinity of P.
At high relative energies.
Does phosphorus in the atmosphere get lost to some process, or why does it need a good source of new material?
 
  • #21
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Phosphorus would remain in the vapour state at some altitude. The only way it would return to the surface is through reaction with metal oxides to form salts, and sulphuric acid there would react preferentially. There is clear evidence of sulphuric acid in the atmosphere.
Phosphoric acid, the oxidation product may condense to a pyrophosphate, or phosphorus pentoxide, or more likely some condensed oxide, possibly it would react with sulphur oxides. I don't think too much is known about phosphorus under the conditions of Venusian lower atmospheric conditions because they are rather hellish and who would bother? Elemental phosphorus would presumably be in the vapour state, but unclear as to what form (P2, P4?) because I don't think too many people study phosphorus under moderately high temperature high pressure conditions with those atmospheric conditions. Phosphine, PH3, will react vigorously with anything that can oxidise it, including at the lower atmosphere any water present. Any acid at cooler regions will form phosphonium salts, that presumably will fall to the lower altitudes. I don't know that anyone has studied the phosphonium dissociation equilibrium at high temperatures and pressures.
My personal view is this signal is probably of photochemical origin, because it attenuates towards the poles, but to get any further I think we need to find out what altitude it comes from, i.e. from the cooler upper atmosphere or the lower hot high pressure atmosphere. Chemists will not know much about this because let's face it, nobody expected phosphine to be there except, it seems, these astronomers. However, I suspect there will be a few papers in a year or so because this will attract interest from those who can provide answers. I think we have to wait for a while and let those who can do the research do it.
 
  • #22
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Chemists will not know much about this because let's face it, nobody expected phosphine to be there except, it seems, these astronomers.
They didn't expect it there either, that's why they looked for it - it's one of the molecules that's hard to explain without life.
At least we'll get more papers looking for possible other origins now.
 
  • #23
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Does phosphorus in the atmosphere get lost to some process, or why does it need a good source of new material?
It's not so much a need for a source, but S(n,p)P and S(n,d)P are potential abiotic sources of P, and H,D. Another potential abiotic source could be 35Cl(n,α)32P. Note 32P (t1/2 = 14.27 d) decays to 32S by beta emission. The microscopic cross-sections for the spallation reactions are on the order of 10s to 100s of mb.

I don't know about the abundance of P on Venus (as in phosphate rock, or in the atmosphere). Various sources mention the composition of the atmosphere of Venus, with CO2 being the most significant component (~96.5%), with nitrogen being some fraction (~3.5%), which may vary, and traces of others.

"The atmosphere of Venus is composed of 96.5% carbon dioxide, 3.5% nitrogen, and traces of other gases, most notably sulfur dioxide." from Wikipedia, https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Composition

But the nitrogen content could be greater, and CO2 less than 96.5%.
https://www.nature.com/articles/s41550-020-1079-2

But sulfur is a trace element and usually (?) as SO2, or SO3, or H2SO4 (?) perhaps depending on elevation from surface.
Minor (ppm): Sulfur Dioxide (SO2) - 150 from https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html

32S(n,d)31P would produce stable, natural P, otherwise the other reactions produce 32P, which decays to 32S by beta emission. The existence of 32P may be an example of secular equilibrium.
https://en.wikipedia.org/wiki/Secular_equilibrium

In https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Composition, there is some discussion of the abundance of D in the atmosphere of Venus. The sources of D are either n-capture by H, or spallation reactions (n,d), (p,d) or other, aside from the solar/stellar fusion reactions.

Venus is known not to have a magnetic field, so there is not protection from the solar wind as there is on earth.

Then there is the matter of chemical stability, and one can refer to Ellingham diagrams as an estimate.
https://en.wikipedia.org/wiki/Ellingham_diagram
http://showard.sdsmt.edu/MET320/Handouts/EllinghamDiagrams/Ellingham_v22_Macro.pdf
The lower the curve, the more stable the reaction/compound. It would appear that CO, CO2 are more stable than PH3. What other species are present, and how stable are they with respect to PH3, and what is the effect of X-ray and gamma radiation on rates of ionization and chemical stability?
 
  • #24
Buzz Bloom
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S(n,p)P and S(n,d)P are potential abiotic sources of P, and H,D.
Hi Astro:

I have been unsuccessful in trying to Locate on the internet an explanation of the notation S(n,p)P and S(n,d)P. Can you help me?

Regards,
Buzz
 
  • #25
Astronuc
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Hi Astro:

I have been unsuccessful in trying to Locate on the internet an explanation of the notation S(n,p)P and S(n,d)P. Can you help me?

Regards,
Buzz
Most introductory nuclear physics or nuclear engineering books would explain the short hand, for describing nuclear reactions. S + n -> p + P => S(n,p)P. The left side are the reactants (the nucleus of S and a neutron), and the right side are the products (proton, p, and P nucleus).

https://www.nuclear-power.net/notation-nuclear-reactions/
http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/nucrea.html (better)
https://www.nndc.bnl.gov/sigma/

d represents a deuteron, t is a triton, α = alpha particle (nuclear of 4He). Spallation reactions occur when high energy (MeV) neutrons, protons, deuterons, alpha particles and other ions strike the nucleus of atoms. In the context of a planetary atmosphere, the gas atoms interact with the solar wind (protons, deuterons, . . . ) and galactic cosmic radiation.
 
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