December 02, 2020, 11:01:50 AM
Forum Rules: Read This Before Posting


Topic: Phosphine on Venus  (Read 651 times)

0 Members and 1 Guest are viewing this topic.

Offline rolnor

  • Chemist
  • Sr. Member
  • *
  • Posts: 1143
  • Mole Snacks: +73/-5
Phosphine on Venus
« on: September 14, 2020, 02:17:34 PM »
You can make phosphine from aluminiumphosphide and acid, is this really impossible on Venus?
https://en.wikipedia.org/wiki/Phosphine

Offline phth

  • Chemist
  • Full Member
  • *
  • Posts: 487
  • Mole Snacks: +35/-4
Re: Phosphine on Venus
« Reply #1 on: September 14, 2020, 07:40:55 PM »
Was it observed? If so then not impossible. There must be a process that affords it. Maybe it's strange under the context of earth's ambient conditions.

Offline rolnor

  • Chemist
  • Sr. Member
  • *
  • Posts: 1143
  • Mole Snacks: +73/-5
Re: Phosphine on Venus
« Reply #2 on: September 14, 2020, 07:47:44 PM »
They propose it must come from some life-form, that it does not form just geo-chemical processes.

Offline Enthalpy

  • Chemist
  • Sr. Member
  • *
  • Posts: 3597
  • Mole Snacks: +295/-57
Re: Phosphine on Venus
« Reply #3 on: September 16, 2020, 05:25:50 AM »
I understand this mediatic event as a typical undesired effect of the ranking of scientists and universities.

"We observed phosphine on Venus" => Who cares
"Life on Venus" => First page of newspapers

The popular echo of a scientist and university, which helps a career, only counts the number of articles in newspapers, the number of comments... but not the scientific quality of the theses nor assertions. Some just write eye-catching cr*p, and alas this works.

Nasa has so much exaggerated that scientists are wary of everything that emanates from there. And what was once specific to the USA has spread meanwhile, especially since the Shanghai ranking.

One sad example was the work of a young astronomer lady who observed the recurrent dimming of a star. She published a set of tentative explanations that she all dismissed, and she refrained from speculation. Zero media impact. Then came a * who made zero effort on the topic but did write "possible Dyson sphere" (= a civilisation exploiting the whole energy of its star) and he got very much media attention, possibly a career boost.

But, well, if it lets scientists learn scientific doubt, that's a good thing.

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1562
  • Mole Snacks: +166/-10
Re: Phosphine on Venus
« Reply #4 on: September 16, 2020, 08:14:24 AM »
I read the paper and you all should too. They did a lot of extremely careful spectroscopy and explored a huge variety of non-biological chemistry as an explanation for the phosphine concentration. They did not find a plausible explanation within 3 orders of magnitude. There are certainly many ways phosphine is formed,however under such a powerful oxidizing atmosphere the lifetime of it is short, and known nonbiological processes produce much smaller amounts.

Life is the best current explanation they could come up with, but they certainly leave the door open for other ideas.

https://www.nature.com/articles/s41550-020-1174-4 its open access.

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1562
  • Mole Snacks: +166/-10
Re: Phosphine on Venus
« Reply #5 on: September 16, 2020, 08:26:37 AM »

Potential pathways for PH3 production
Potential PH3-production pathways in the Venusian environment are discussed in detail in the Supplementary Information (W. Bains et al., manuscript in preparation; summarized in Extended Data Fig. 10). Two possible classes of routes for the production of PH3 were considered: photochemical production or non-photochemical chemistry.

For photochemical modelling, we created a network of reactions of known kinetic parameters59 that could lead from H3PO4 (phosphoric acid) to PH3 (phosphine), by reaction with photochemically generated radicals in the Venusian atmosphere. Where reactions were possible but no kinetic data for the phosphorus species were known, homologous nitrogen species reaction kinetics were used instead, validated by comparing reactions of analogous nitrogen and phosphorus species. The maximum possible rate for reductive chemistry in this network was compared with the destruction rate as a function of altitude.

Non-photochemical reactions were modelled thermodynamically. For surface and atmospheric chemistry, we created a list of chemicals, their concentrations and reactions, for all potential PH3 production reactions. Phosphorus species abundances were calculated themodynamically and assumed to be in equilibrium with liquid/solid species at the cloud base. The free energy of reaction, indicating whether the net production of PH3 was thermodynamically favoured, was calculated using standard methods (see Supplementary Information for details). None of the reactions favour the formation of PH3, on average having a free energy of reaction of +100 kJ mol−1 (Extended Data Fig. 7).

Modelling the subsurface chemistry was approached via oxygen fugacity (fO2) (ref. 60), the notional concentration of free oxygen in the crustal rocks. We model the equilibrium between phosphate and PH3, for temperatures between 700 K and 1,800 K, at 100 or 1,000 bar, and with 0.01%, 0.2% and 5% water. Oxygen fugacity of plausible crust and mantle rocks based on Venus lander geological data is 8–15 orders of magnitude too high to support reduction of phosphate, so degassing of mantle rocks would produce only trivial amounts of PH3. Volcanic, lightning and meteoritic delivery were calculated based on parallels with terrestrial rates of events within Venusian atmosphere, and were calculated to be negligible.


Supplementary Info has even more detail and concepts, and another whole paper on it is pending

Offline rolnor

  • Chemist
  • Sr. Member
  • *
  • Posts: 1143
  • Mole Snacks: +73/-5
Re: Phosphine on Venus
« Reply #6 on: September 16, 2020, 11:04:22 AM »
Thanks wildfyr, interresting. I still think odds are in favour of a non-biological origin, there must be an extrem amount of chemistry going on with this hot surface?

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1562
  • Mole Snacks: +166/-10
Re: Phosphine on Venus
« Reply #7 on: September 16, 2020, 05:42:33 PM »
Extremely hot, acidic oxidizing chemistry sure doesn't favor a reducing agent like PH3 though! You're right, there is a good likelihood its not life, but this signal sticks out like a sore thumb. Phosphine is one of the chemicals astrobiologists have decided is a good "fingerprint" for life when looking at planets in other star systems, which is probably why they bothered to train a telescope on Venus just to try out the concept.

Offline rolnor

  • Chemist
  • Sr. Member
  • *
  • Posts: 1143
  • Mole Snacks: +73/-5
Re: Phosphine on Venus
« Reply #8 on: September 16, 2020, 07:36:46 PM »
No, thats true, phosphine is very reducing. Wonder if they know what is under ground on venus, deep inside, maybe its a large reducing lump of phosphor?

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1562
  • Mole Snacks: +166/-10

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1562
  • Mole Snacks: +166/-10
Re: Phosphine on Venus
« Reply #10 on: September 16, 2020, 10:29:59 PM »
That other small spike is from an episode of breaking bad. *rolls eyes*

Offline rolnor

  • Chemist
  • Sr. Member
  • *
  • Posts: 1143
  • Mole Snacks: +73/-5
Re: Phosphine on Venus
« Reply #11 on: September 17, 2020, 01:30:01 PM »
One could wonder what type of life it could be on Venus, it must be up in the atmosphere I guess, the surface is to hot for carbon-based life as whe know it. I think the most tough extremophiles on earth can live at 170°C?

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1562
  • Mole Snacks: +166/-10
Re: Phosphine on Venus
« Reply #12 on: September 17, 2020, 01:45:20 PM »
Almost certainly atmosphere based if they are there. The upper atmosphere of Venus can actually be quite pleasant.... aside from the clouds of sulfuric acid vapor. In the tropopause temps are around 25C and air pressure about the same.

Offline Enthalpy

  • Chemist
  • Sr. Member
  • *
  • Posts: 3597
  • Mole Snacks: +295/-57
Re: Phosphine on Venus
« Reply #13 on: September 29, 2020, 09:42:54 AM »
Thanks for linking the paper!

I like the authors' formulation. They never claim to have ruled out all abiotic processes.

Offline rolnor

  • Chemist
  • Sr. Member
  • *
  • Posts: 1143
  • Mole Snacks: +73/-5
Re: Phosphine on Venus
« Reply #14 on: September 29, 2020, 12:59:08 PM »
One could wonder about this very acidic atmosphere, proteins and lipids should be hydrolyzed but whe have bacteria on eart that thrives in sulphuric acid, but not concentrated though? The suphuric acid rain on Venus is maybe  diluted? But that would mean there is liquid water?

Sponsored Links