# Phosphine, yes — but where are the organic compounds on Venus?

There has been much speculation in recent news about the finding of phosphine on Venus, and what may be producing it.

At the same time, when we look for clues of life elsewhere in the Solar System, we look for and have found at least some of the organic compounds associated with such life (as we know it). But what about such organic chemistry on/above Venus? While engineers from the Los Alamos National Laboratory are working on a probe to find organic compounds on Venus, for now I am unaware of any current evidence except, maybe, carbonyl sulfide.

So am I missing something? Is more extensive organic chemistry already known (not just speculated) on Venus?

Note: an accepted answer will indicate, with references if available, that either no organic compounds have yet been found or that they are known, directly aming the clouds of Venus as they are on Mars and other life candidates.

January 2021 update: Alas, the phosphine is no more. It appears to have been sulfur dioxide all along.

• Perhaps the answer is in this article: "Therefore, the question is: what matter may life on the planet be built on? We consider chemical compounds stable at high temperatures that may be a base for hypothetical Venusian life. We conclude that to explore Venus's hypothetical life, a new dedicated mission, much more advanced than the VENERA missions, should be sent to the planet." Article "Hypothetical signs of life on Venus: revising results of 1975 – 1982 TV experiments" L V Ksanfomality, L M Zelenyi, V N Parmon and V N Snytnikov © 2019 – A. Rumlin Sep 15 '20 at 17:10
• Interesting take, although the current focus is away from the high temperature conditions. That being so, if somehow there were non-carbon based life on Venus then we'd miss it looking for the usual organic compounds. – Oscar Lanzi Sep 15 '20 at 17:14
• From the article in Nature named "Phosphine gas in the cloud decks of Venus' : "We also rule out the formation of phosphorous acid ($H_3PO_3$). While phosphorous acid can disproportionate to PH3 on heating, its formation under Venus temperatures and pressures would require quite unrealistic conditions, such as an atmosphere composed almost entirely of hydrogen..." – Cornelis Sep 16 '20 at 9:40
• @Cornelisinspace I read that as saying they adopted the overall elemental phosphorus abundance data, but not the assumptions about the specific chemicals involved (P4O6, etc) - "its chemical speciation is not known". – Andrew Sep 16 '20 at 12:33
• Yes, so I read the ref. 1 again that tells us P4O6 with the sulfuric acid droplets transforms it into phosphoric acid droplets with SO2 release . Couldn't that transform the phosphorus into the +5 oxidation state ? And after that the droplets move down to 25 km where evaporation into P4O10 (P2O5) would occur. – Cornelis Sep 16 '20 at 15:40

From Exploring Organic Environments in the Solar System, the chapter "The $$\text{CO}_2$$-Dominated Atmospheres of Venus and Mars" (page 91):

..., making $$\text{CO}_2$$ highly stable in their atmospheres. As a result, more complex carbon-bearing species are not produced in the atmospheres of either Mars or Venus.
Ion-molecule reactions and electrical discharges also do not initiate any further carbon chemistry in either planet's atmosphere. Thus, the only carbon-bearing species observed in the martian atmosphere are $$\text{CO}_2$$ and $$\text{CO}$$. On Venus, $$\text{COS}$$ has been observed in addition to $$\text{CO}_2$$ and $$\text{CO}$$, and is thought to be produced at the surface by equilibrium reactions between $$\text{CO}_2$$,$$\text{CO}$$, and $$\text{FeS}_2$$ at the high temperature and pressure there.

Venus: The Atmosphere, Climate, Surface, Interior and Near-Space Environment of an Earth-Like Planet, Table 3 gives an overview of (all known) species in Venus's atmosphere.
They are: $$\text{CO}_2, \text{N}_2, \text{Ar}, \text{Ne}, \text{H}_2\text{O}, \text{HDO}, \text{SO}_2, \text{COS}, \text{CO}, \text{HCl}, \text{HF}, \text{O}, \text{OH}, \text{H}.$$

Conclusion: although no articles or papers were encountered that state that no organic compounds (compounds with carbon-hydrogen bonds) were found on Venus, the two cited surveys of the atmosphere demonstrate that indeed they were not.

• Mars has had methane sporadically identified in its atmosphere, plus more complex organic compounds on the ground. However, it is unlikely that either sporadic presence or organics on the ground would be empirically viable alternatives on Venus. – Oscar Lanzi Sep 21 '20 at 19:20
• "They are: ... H." Uh-oh. Hydrogen atoms could reduce phosphorus compounds to phosphine. – Oscar Lanzi Sep 22 '20 at 12:30
• @OscarLanzi A very slow reaction of S + HCl seems to result in the formation of $H_2S$ in the lower atmosphere. ui.adsabs.harvard.edu/abs/2018cosp...42E1834K/abstract – Cornelis Sep 22 '20 at 13:57
• there is new information which I have summarized. Your thoughts on that? – Oscar Lanzi Oct 18 '20 at 0:06
• @OscarLanzi Glycine is discovered on Venus. Also, see this updated video on YT: youtube.com/watch?v=vK3-UEJH_zA – Nilay Ghosh Nov 1 '20 at 13:40

Not related to phosphine or any organophosphorus compounds, but a trace amount of nitrogen containing organic compounds is hypothesized to be present. According to a 1974 paper1, a gas composition similar to Venusian atmosphere was made and was electrically discharged. The products were measured by mass spectrometry:

Based on the detection of ammonia in the Venus atmosphere, and the suggested presence of hydrogen chloride, a structure for the Venus atmosphere was suggested as having 3 cloud layers, consisting of ammonium chloride (30 to 50 km above the ground), a mixture of ammonium bicarbonate and ammonium carbamate ($$\text{NH}_2\text{COONH}_4$$) from 50–60 km, and water ice crystals above this. There is a strong possibility of electrical discharge in the atmosphere as a result of thermal convective turbulence, which in the case of the slightly reducing atmosphere outlined above could lead to organic compound formation.

The hypothesis was tested experimentally by passing a 60 KV spark from platinum electrodes through a gas mixture of composition: $$\text{N}_2$$(0.2%), $$\text{NH}_3$$ (2%), Water (5%), $$\text{O}_2$$ (0.6%), $$\text{CO}_2$$ (remainder), for 8 hr. The products were analysed by mass spectrometry and amino acid analysis by ion exchange. Methane and formaldehyde were identified by MS, and glycine and alanine by the amino acid analyzer.

The presence of organic compounds in the Venus atmosphere is therefore a strong possibility.

Reference

1. Otroshchenko V.A., Surkov Y.A. (1974) The Possibility of Organic Molecule Formation in the Venus Atmosphere. In: Oró J., Miller S.L., Ponnamperuma C., Young R.S. (eds) Cosmochemical Evolution and the Origins of Life. Springer, Dordrecht. https://doi.org/10.1007/978-94-010-2239-2_40
• Yes, I am aware of this work. However, the gas composition used does not match what other sources report for the Venusian atmosphere. Clouds aside (and these are primarily sulfuric acid, not ammonium salts), the major components I typically read about are carbon dioxide, nitrogen, a small amount of sulfur dioxide and traces of various compounds -- but not ammonia. – Oscar Lanzi Sep 17 '20 at 12:31

Update:

October 2020: It appears this barrier has been crossed with the identification of glycine in the atmosphere of Venus. This link provides an abstract from which the pdf may be downloaded without a paywall. The title, authors and abstract are given below.

Detection of simplest amino acid glycine in the atmosphere of the Venus

Arijit Manna,1 Sabyasachi Pal,2,1∗ Mangal Hazra1

Amino acids are considered to be prime ingredients in chemistry, leading to life. Glycine is the simplest amino acid and most commonly found in animal proteins. It is a glucogenic and non-essential amino acid that is produced naturally by the living body and plays a key role in the creation of several other important bio-compounds and proteins. We report the spectroscopic de- tection of the presence of the simplest amino acid glycine (NH2CH2COOH) with transition J=13(13,1)–12(12,0) at ν=261.87 GHz (16.7σ statistical significance) with column density N(glycine)=$$7.8×10^{12} \text{cm}^{−2}$$, in the atmosphere of the solar planet Venus using the Atacama Large Millimeter/submillimeter Array (ALMA). Its detection in the atmosphere of Venus might be one of the keys to understand the formation mechanisms of prebiotic molecules in the atmosphere of Venus. The upper atmosphere of Venus may be going through nearly the same biological method as Earth billions of years ago.

• Good news, of course , although glycine already has been detected on some comets. The next question could be, is it formed in the atmosphere, by lightning for example, or could it even be a residue of a polypeptiide ?:) – Cornelis Oct 18 '20 at 14:39
• Exactly. Get at least one organic compound into play, then we can see its/their origin. – Oscar Lanzi Oct 18 '20 at 14:51
• The Russians thought they had detected NH3 in 1974 and published a conference paper about the possibiliy of organic molecule formation. But the detection was wrong and since then no ammonia was ever found. (as far as I know). One would think ammonia is needed. link.springer.com/chapter/10.1007/978-94-010-2239-2_40 – Cornelis Oct 18 '20 at 16:35
• Shouldn't this news hit the headlines like PH3 did ? Maybe you could ask a new question with it ? – Cornelis Oct 18 '20 at 18:30
• I did see it in the news. I thought it was relevant to this question. – Oscar Lanzi Oct 18 '20 at 18:45