For cyanobacteria metal ions like K+, Mg+ and other essential nutrients like phosphorus are vital for growing and to expand.

So they could only thrive in the clouds of Venus if at least metal ions could be brought there, possibly in the form of hydroxides, like KOH and Mg(OH)2.
With the sulfuric acid, those hydroxydes would form water and metal sulfates.

If the amount of metal hydroxides could be distributed sufficiently, then could the produced metal sulfates gather enough water to stay in the clouds or would they gradually fall down to the lower regions of the atmosphere ?

Venera and Vega descent probes have found, besides phosphorus, iron in the atmosphere, so is weight not that important to be able to stay in certain regions ?

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    $\begingroup$ No, you are not going to have magnesium hydroxide briught to the clouds from the surface. It would decompose. $\endgroup$ May 23, 2019 at 1:32
  • $\begingroup$ @OscarLanzi Thank you for your comment, but i didn't write that the metal hydroxides should come from the surface ( of Venus ). On the surface of Venus magnesium hydroxide would indeed decompose, but not in the clouds. $\endgroup$
    – Cornelis
    May 24, 2019 at 12:30

1 Answer 1


Weight is not really an issue here. Ice/water droplets have a far higher "molecular weight" than the ions of salts, yet our Earth is always adorned by clouds. Divide any weight into small enough pieces and the air currents on a planet with a decent atmosphere can hold the pieces aloft for an extened period of time.

Getting the weight of the salt divided into individual molecules/ion clusters, through their volatility, is surely the more important factor. Chlorides are relatively volatile salts, and the element chlorine is known on Venus, so let's compare the volatility of some common metal chlorides by tabulating their normal boiling points. All values are taken from the Wikipedia articles for the compounds; water of hydration is ignored since it would boil away before the salt vaporizes appreciably.


$\text{MgCl}_2\text{ = }1412°\text{C}$

$\color{blue}{\text{AlCl}_3\text{ = }180°\text{C}}$


$\text{CaCl}_2\text{ = }1935°\text{C}$

$\text{FeCl}_2\text{ = }1023°\text{C}$

$\color{blue}{\text{FeCl}_3\text{ = }316°\text{C}}$

As we can see, aluminum and iron, the latter in the +3 oxidation state, form readily volatile chlorides that can carry the metals into the clouds, whereas the other metals we expect to commonly find in terrestrial planet crusts (alkali and alkaline earth metals) can't be easily vaporized this way. The favored chlorides have a lot of covalent character and can readily convert themselves to relatively volatile molecules, whereas the predominantly ionic chlorides of the common alkali and alkaline earth metals can't get there even on Venus.

We see iron in the Venusian atmosphere, potentially available for organisms; but if those organisms depend on the alkali or alkaline earth metals given above, including potassium and magnesium mentioned by the OP, life would literally be tough to manage.

  • $\begingroup$ Thank you again for the valuable information, but the idea in the question is that the hydroxides would produce sulfates within the the sulfuric acid clouds of Venus. So the question would become rather if those sulfates with their water of hydration could stay in solution within the acidic droplets ? $\endgroup$
    – Cornelis
    May 26, 2019 at 13:59
  • $\begingroup$ Chlorides could also be converted to sulfates, actually, at least for sodium chloride on Earth; look at the laboratory synthesis of hydrogen chloride here. $\endgroup$ May 26, 2019 at 21:25

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