Biological Agent Phosphine Found on Venus

[Greg Bernhardt]

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

 

[sysprog]

That's seems to be to be at least a moderate confirmation of one or more of Fred Hoyle's speculations.

Quote

 

[Ygggdrasil]

Phosphine is present on Saturn and Jupiter, presumably it is produced abiotically there:
https://www.sciencedirect.com/science/article/pii/S0019103509001328

 

[Bandersnatch]

Phosphine is present on Saturn and Jupiter, presumably it is produced abiotically there:
https://www.sciencedirect.com/science/article/pii/S0019103509001328

As I understand the news bit, the chemical processes producing it on the gas giants are not possible on Venus.

 

[mfb]

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.

 

[websterling]

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?

 

[glappkaeft]

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?

 

[sysprog]

H

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 $\dots$

 

[TeethWhitener]

https://en.m.wikipedia.org/wiki/Betteridge's_law_of_headlines

The group also notes that for phosphine to be a strong indication of biological activity, it would probably need to be at significantly higher concentration than they see it (ppb levels).

 

[websterling]

https://en.m.wikipedia.org/wiki/Betteridge's_law_of_headlines

I'm more familiar with this as "Hinchliffe's Rule" and can't believe I didn't see it when I wrote the title. I've been known to call others on it.

 

[Ygggdrasil]

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.

 

[Tom.G]

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

 

[Tom.G]

There is an article on the front page of the Los Angeles Times today (Sep. 14, 2020). Interviews with some of the scientists involved and a bit of their thought processes leading to possible sources of the phosphine.
https://www.latimes.com/science/sto...traterrestrial-life-in-venus-clouds-phosphine

Cheers,
Tom

 

[AstroMaksud]

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.

 

[Ian J Miller]

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.

 

[Astronuc]

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, . . .

 

[Ygggdrasil]

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.

 

[Ian J Miller]

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.

 

[Astronuc]

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

 

[mfb]

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?

 

[Ian J Miller]

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.

 

[mfb]

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.

 

[Astronuc]

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 (t_1/2 = 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?

 

[Buzz Bloom]

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

 

[Astronuc]

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.

 

[Ian J Miller]

The problem I have with neutron capture to make this phosphine is, according to the Nature Astronomy paper, under the most favourable reasonable phosphine lifetimes, a million molecules have to be made every second per cm^2. That is a rather severe neutron flux. Which raises a further question for me: if the star is throwing out that flux of neutrons, why are the stellar levels of 16O and 14N higher (or the heavier isotopes lower) than anywhere else in the solar system?

As to where the deuterium came from, that is another very important question. The usual answer is that Venus once had as much water as Earth (No evidence is offered for that, though) and photochemistry knocked the hydrogen atoms off and these were lost to space. The deuterated water was slightly heavier, so ordinary water was slightly favoured. I do not believe that because it raises the question, where is the oxygen? If it is in the CO2, that would mean there had to be a lot less water to start with, and the carbon had to be something like methane (to react with the oxygen).

Sulphur and phosphorus will be quite plentiful on Venus, but they will be solids, the phosphates dispersed in rocks, while much of the sulphur binds with iron and forms an iron sulphide layer around the iron as part of the core, at least that is what models suggest.

My answer to why the high levels of deuterium go like this. Where do the elements that are in the atmosphere come from? There is a variety of reasons why comets or chondrites cannot be the answer. For comets, there should be at least 20,000 times more 36Ar. For chondrites, the isotopes are wrong, and as an example the isotope ratios of oxygen in chondrites are quite different from Earth. If the volatiles came from chondrites, the Moon should also have been struck, and while you can argue that the volatiles would be lost, the rocks are not. Now Earth's rocks have been tectonically recycled, so those chondritic isotopes would be dispersed into the mantle, but not on the Moon, so why does the Moon have the same ratio as Earth? Also, why do the atmospheres of the rocky planets all have different ratios of components, and none have the xenon expected of chondrites?

As I see it, the simplest explanation is that the planets only accreted solids. The water came from hydration of silicates, and especially aluminosilicates, while the carbon and nitrogen came as carbides and nitrides, made from standard chemistry expected in the accretion disk while the star was forming. That requires the solids NOT to get swept into the star then, but at least it explains why the planets contain most of the system's angular momentum. The solids then react with water to generate reduced gases, and these involve hydrogen transfer. The deuterium is retained by the water through the chemical isotope effect, and any hydrogen formed is preferentially lost to space.

 

[Astronuc]

That is a rather severe neutron flux. Which raises a further question for me: if the star is throwing out that flux of neutrons, . . .

Neutrons in the planetary atmosphere do not come from the sun (stars), but the neutrons to which I refer originate in spallation reactions from high energy protons, or deuterons, and even alpha particles, with light elements such as C, N, O in the respective atmosphere.

One raises many other issues related to element and isotope abundance and ratios.

 

[Ian J Miller]

Thanks, but it is still a puzzle to me why the same sort of reactions do not increase the heavier isotopes in the sun. Is it reasonable to assume that any such neutrons made would react preferentially with hydrogen simply because there is so much more of it?

 

[snorkack]

Does phosphorus in the atmosphere get lost to some process, or why does it need a good source of new material?

1) Dilute sulphuric acid is not a kinetically good oxidant (which is why active metals give off hydrogen from dilute sulphuric acid) but hot concentrated sulphuric acid is oxidant and oxidizes metals such as Cu, Hg and Ag. Which is why it might oxidize phosphine:
H₃P+H₂SO₄=H₃PO₄+H₂S
H₃P+4H₂SO₄=H₃PO₄+4SO₂+4H₂O
3H₃P+4H₂SO₄=3H₃PO₄+4S+4H₂O
All the ways you end up with H₃PO₄ dissolved in strong sulphuric acid.
2) While exploring what happens to strong acids in Venus´´ lower atmosphere is a bother, what happens to strong acids when heated in a pot in a laboratory is reasonably well known, if not so well published.

Basically, at 1 bar total vapour pressure, sulphuric acid loses mostly water vapour till it is concentrated to over 90 % and 200 Celsius. Then it starts giving off appreciable fraction of sulphuric acid vapour as well, till at 338 Celsius it boils at constant composition of 98,3 % (by mass) sulphuric acid.
Azeotropic mixture compositions depend on pressure. When sulphuric acid is evaporated away at lower pressure (as would be the case in Venus´ atmosphere, mostly carbon dioxide not sulphuric acid vapour), the evaporation temperature is of course lower - and the azeotropic concentration of sulphuric acid is higher.

Now, phosphoric acid is less volatile than sulphuric acid. When boiled off by itself, again under 1 bar vapour pressure, the azeotropic mixture is slightly towards P₂O₅, near HPO₃, at 869 Celsius.
Therefore, when sulphuric acid with phosphoric acid admixture rains down and is evaporated in hot lower atmosphere of Venus, HPO₃ should remain, at first.
What would become of HPO₃ that rains on Venus? Any way to return it?

 

[Astronuc]

Is it reasonable to assume that any such neutrons made would react preferentially with hydrogen simply because there is so much more of it?

I plotted the cross-sections for radiative capture (n,γ) and elastic scattering (n,el). They show a greater probability of scattering over the energy range 0.001 eV to 100 MeV. For the radiative capture, the probability is greater for H until about 200 keV where the capture cross section of O becomes greater. I do not know the neutron energy spectrum of solar neutrons, but the following might provide an answer: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010JA015930

Based on the cross-sections, it would appear that a neutron is more likely to scatter than be captured such that it would eventually decay (t_1/2 = 613.9 s) to a proton, electron and antineutrino.

 

[Ian J Miller]

I plotted the cross-sections for radiative capture (n,γ) and elastic scattering (n,el). They show a greater probability of scattering over the energy range 0.001 eV to 100 MeV. For the radiative capture, the probability is greater for H until about 200 keV where the capture cross section of O becomes greater. I do not know the neutron energy spectrum of solar neutrons, but the following might provide an answer: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010JA015930

Based on the cross-sections, it would appear that a neutron is more likely to scatter than be captured such that it would eventually decay (t_1/2 = 613.9 s) to a proton, electron and antineutrino.

Thanks for the information.

 

[Ian J Miller]

As for recycling phosphorus in the Venusian atmosphere, the phosphorus oxide systems are very complicated because they tend to condense and dehydrate, but if they dehydrate to phosphorus pentoxide, that sublimes at 1 atmosphere at 300 degrees C (according to my copy of the Handbook of Chemistry and Physics) so if sulphuric acid could be revolatalised from the surface of Venus, so could phosphorus, but this presupposes it has not formed a solid salt. If it could form something like a phosphoryl halide it would volatalise. Phosphorus would normally be expected to be some calcium salt on a rocky planet and dispersed in the silicates. I am unaware of any detection of phosphorus in the Venusian atmosphere, but that may reflect more my ignorance than anything else.

 

[Vanadium 50]

@Astronuc , I agree with you that the neutrons in question are secondaries produced by spallation. However, I don't see how the primary cosmic ray flux can be high enough. I don't have a good definitive reference for this number at a few MeV, but it's got to be of order a few per square meter per second. That's quite a jump to the million per square centimeter per second that @Ian J Miller cites.

 

[snorkack]

As for recycling phosphorus in the Venusian atmosphere, the phosphorus oxide systems are very complicated because they tend to condense and dehydrate, but if they dehydrate to phosphorus pentoxide, that sublimes at 1 atmosphere at 300 degrees C (according to my copy of the Handbook of Chemistry and Physics) so if sulphuric acid could be revolatalised from the surface of Venus, so could phosphorus, but this presupposes it has not formed a solid salt.

SO₃ boils at 45 Celsius, but for one it is liable to polymerize to solid in which case it sublimes t 62 Celsius, and for another, it is highly hygroscopic, forming azeotrope H₂SO₄ with a small amount of H₂O, which boils at 338 Celsius.
P₄O₁₀ boils at about 360 Celsius, but is also liable to polymerize (then boils round 700 Celsius) and is highly hygroscopic, forming azeotrope HPO₃ with small amount of P₂O₅, which boils at 869 Celsius.

 

[mfb]

Based on the cross-sections, it would appear that a neutron is more likely to scatter than be captured such that it would eventually decay (t1/2 = 613.9 s) to a proton, electron and antineutrino.

Neutrons won't survive that long unless you carefully prepare a trap for them in the lab. A cross section for scattering that's 100 times as large just means you get an average of 100 scattering processes before a capture (+- something because the energy changes from the scattering processes). That's still tiny fractions of a second.

 

[Ygggdrasil]

Another team attempted to confirm the presence of phosphine in the atmosphere of Venus by examining IR spectra and did not observe signals at the wavelengths expected for phosphine:

A stringent upper limit of the PH3 abundance at the cloud top of Venus
https://arxiv.org/abs/2010.07817

Abstract

Following the announcement of the detection of phosphine (PH3) in the cloud deck of Venus at millimeter wavelengths, we have searched for other possible signatures of this molecule in the infrared range.
Since 2012, we have been observing Venus in the thermal infrared at various wavelengths to monitor the behavior of SO2 and H2O at the cloud top. We have identified a spectral interval recorded in March 2015 around 950 cm−1 where a PH3 transition is present.
From the absence of any feature at this frequency, we derive, on the disk-integrated spectrum, a 3-σ upper limit of 5 ppbv for the PH3 mixing ratio, assumed to be constant throughout the atmosphere. This limit is 4 times lower than the disk-integrated mixing ratio derived at millimeter wavelengths.
Our result brings a strong constraint on the maximum PH3 abundance at the cloud top and in the lower mesosphere of Venus.

 

[sophiecentaur]

That's seems to be to be at least a moderate confirmation of one or more of Fred Hoyle's speculations.

Quote

I think the guy really deserves a retrospective break. At the time he favoured the Steady State solution, he was by no means the only one and the CMBR measurements were only available after he published his views. Not surprisingly, he didn't go down without a struggle. And he did invent the term "Big Bang" (though it was in an attempt to put the idea down.)

Mainstream Science can often be pretty unforgiving of 'good Scientists'. Take poor old Eric Laithwate, who was a very competent Electrical Engineer but just wasn't allowed to suggest that reactionless drive might be needed in order to 'explain' the results of some of his dodgy Maths.

Science is a rough business and shows no sympathy for people who rock the boat. Paradigm changes do occur though but history is written by the winners, as in all of life.

 

[Ian J Miller]

I would be very nervous of assigning a signal at 950 cm-1 to phosphine. Acid chlorides, phosphates, and certain nitrogen-oxygen bonds can give signals in this region, and when talking about the upper atmosphere, as seen in Earth's atmosphere, some rather strange molecules are formed in very low concentration due to UV photochemistry. Phosphine is not the only molecule that could give the signal.

 

[sophiecentaur]

I would be very nervous of assigning a signal at 950 cm-1 to phosphine. Acid chlorides, phosphates, and certain nitrogen-oxygen bonds can give signals in this region, and when talking about the upper atmosphere, as seen in Earth's atmosphere, some rather strange molecules are formed in very low concentration due to UV photochemistry. Phosphine is not the only molecule that could give the signal.

I talked to Emily Darnell Maunder, who was a member of the team. I asked her about the sort of signal to noise ratio for their measurement and she quoted well above 10dB. So that is a Reasonable confidence limit, I would have thought.

 

[Ian J Miller]

I don't doubt they properly recorded a signal. The question is, what caused it?

 

[Ygggdrasil]

I would be very nervous of assigning a signal at 950 cm-1 to phosphine. Acid chlorides, phosphates, and certain nitrogen-oxygen bonds can give signals in this region, and when talking about the upper atmosphere, as seen in Earth's atmosphere, some rather strange molecules are formed in very low concentration due to UV photochemistry. Phosphine is not the only molecule that could give the signal.

The significance is not that they observed a signal at 950 cm-1, it's that the did not observe a signal at that wavenumber (especially not the intensity of signal they would expect to see if phosphine were as abundant as claimed in the Nature Astoronomy paper). This would seem to suggest that either phosphine is much less abundant than claimed or that the signal observed by the Nature Astronomy paper is not due to phosphine.

To quote Encrenaz et al. pre-print:

the detection of at least one other PH3 transition, in the infrared or in the millimeter/sub-millimeter range, is definitely needed to confirm the PH3 detection in Venus.

 

[Ian J Miller]

Yes, the upper limit is significant. I was more concerned with whether there was any? I noticed the factor of 4, but again could it be something else there as well? The something else does not have to be equivalent at both frequencies. We still don't know, and I guess I am simply suspicious of phosphine being there.

 

[sophiecentaur]

I don't doubt they properly recorded a signal. The question is, what caused it?

The thing about spectroscopy is that frequency can be measured with more accuracy than any other quantity (it goes wit time). ‘They’ used a lot of previous data as well and the the probability of another explanation for the (precise) frequency arising any other way was considered to be very low.
It’s a system that’s been used for finding the components of all astronomical objects. If you doubt it’s veracity then you need to doubt an awful lot of other discoveries.
I’m not sure there is actually any alternative explanation for the line.

 

[andrew s 1905]

Yes wavelength is accurately measured but assignments us a different problem. There are many lines in high resolution spectra and a single line is not reliable proof . Hence the need for confirmation. This is standard practice and does not challenge all of spectroscopy.
Regards Andrew

 

[sophiecentaur]

Yes wavelength is accurately measured but assignments us a different problem. There are many lines in high resolution spectra and a single line is not reliable proof . Hence the need for confirmation. This is standard practice and does not challenge all of spectroscopy.
Regards Andrew

That is a reasonable statement but absolute frequency gives an absolute Energy transition and, if there are no other possible candidates for the phenomenon then what alternatives are there? I know that the various series are often used for identifying elements and that can be used when the light levels are very low.

Have there been any challenges, other than yours, though? The practical details are very important here - also the precise values of measurements which were obtained from a vast amount of existing data. The team stopped, once their confidence in the result was high enough. I think the data is all public domain so you could, in principle, do the same analysis yourself. (Domestic data connection might be a bit limiting, I suppose.

I'm always impressed with the apparent certainty that spectroscopy gives us; the numbers seem to be reliable.

 

[andrew s 1905]

If I recall correctly they did consider sulphur dioxide as a possibility but dismissed it. You also have to consider the conditions which can broaden the lines, various relative velocities (wind speed, Earth Venus relative velocity) which can shift the lines so it is not as absolute as you might think.

It may well be PH3, but it could be a line from an unnconsiders molecule hence the need for confirmation. I did see a paper where it was detected in retrospect in a Venus probes data. I don't have the reference to hand.

Many lines in the solar spectrum remain unidentified even today after years of study.

Regards Andrew

PS I think only the reduced data is available and in any case without experience of the telescopes involved and the necessary calibration data it is not possible to check.

 

[Ygggdrasil]

Although I am not too familiar with these fields, I am surprised that the authors could claim detection of phosphine based detection of only a single spectral line, especially since the presence of phosphine on Venus is quite unexpected. Is this standard of evidence common across astronomy? Perhaps this limitation of the paper is why it appeared in Nature Astronomy (a relatively new journal published by a for-profit publisher that was likely looking for publicity) rather than a more prestigious journal.

 

[Ian J Miller]

An infrared signal is generated by an energy transition between two states, usually vibrational states, and in chemistry the frequency is often set by what happens in a functional group, and modifed by "the rest of the molecule". If you check a chart of infrared signal possibilities, you will see that a number of molecules could generate a 950 cm-1 line. You need the rest of the signals to be more certain. What concerns me more is that nitrogen-oxygen species can give signals there, and in the Venusian atmosphere it is unclear what could be generated by photochemistry. I am not saying it is not phosphine, but simply that given the difficulties in forming enough phosphine to be stable sufficiently long to generate that signal I suggest a little caution.

 

[andrew s 1905]

A re analysis of the alma data finds no evidence for phosphine Re analysis
Regards Andrew

 

[Vanadium 50]

Without Alma, the JCMT data is not very convincing. (If you turn it upside down, you see signals at least as significant)