Re: Multiple thalassogens


Logan Kearsley wrote:
> <chornedsnorkack@xxxxxxxxxxxx> wrote in message
> <snip>
> > > > > > Also, I suspect that the bases would react with carbonic acid whether
> > > > > > it is carbonic acid dissolved in excess water or carbonic acid
> > > > > > dissolved in excess liquid CO2.
> > > > >
> > > > > Hence why I specified everything that would make carbonates being used up to
> > > > > leave the excess.
> > > > >
> > > > But even if there are only traces of water, and I suspect even if there
> > > > are no traces, large quantities of CO2 or SO2 available for oceans
> > > > would react with bases. Unless the bases are used up - but if they are,
> > > > CO2/water oceans would work fine.
> > >
> > > CO2 and water all by themselves? Or carbonic acid and whichever one (CO2 or
> > > water) there is an excess of?
> > > Mewonders what sort of geology that would make for....
> > >
> > Water and CO2 have mutual limited solubility. If you have water and a
> > small amount of CO2, what you get is dilute carbonic acid. You need a
> > lot of CO2 before the water is saturated and there is saturated
> > carbonic acid + liquid carbon dioxide with some water dissolved in it.
>
> So you would end up with liquid CO2 either floating on top of or sandwiching
> a layer of saturated carbonic acid, with no pure water layer, correct?
>
Correct. Earth has no pure water layer either - fresh water is
saturated in respect to CO2 available in air and has formed dilute
carbonic acid whose pH is 5,5 - much lower than 7,0 of pure water

> > > > > > > But what about an ocean of SO2 floating on an ocean of CO2,
> > > > > >
> > > > > > Dubious. Liquid SO2 is miscible with a plenty of organic solvents, I
> > > > > > suspect with CO2 as well.
> > > > >
> > > > > Hm. I find that odd, as SO2 is polar and CO2 is not.
> > > >
> > > > The difference is there, but not that huge.
> > >
> > > Almost as big as it is with water. CO2 is completely non-polar, while SO2
> > > has a dipole moment of 1.63 D- less than water at 1.85 D, but still higher
> > > than ammonia at 1.47 D.
> > >
> > Comparing water and SO2, wou will notice that SO2 has a molecular mass
> > of 64 and water has 18, yet SO2 boils at -10 Celsius and water at +100.
> > The difference is that water can form hydrogen bonds and SO2 cannot,
> > lacking available H.
>
> True. That brings up the possibility of another thallasogen: H2SO4, which
> has a much wider liquid range than water.
> I assume H2SO4 would remain highly corrosive even when not in solution with
> water,

I assume that especially when not in solution...

> but would it be possible for it to coexist with a CO2 ocean?

I suppose so. Depending on what the bottom is, though.

Venus now has clouds of around 75% H2SO4 - the concentration ought to
vary, perhaps someone can comment. The acid rains constantly down, but
evaporates in hot lower atmosphere without reaching the surface. The
vapour somehow returns back up and condenses.

Venus also has 90 atm CO2. But the lower levels are hot.

If Venus were cooled appreciably then one would expect the sulphuric
acid rain to get further down. If the temperature were low enough, or
if the total quantity of available sulphuric acid were increased, the
acid might reach the surface. Then it depends on whether there are
available bases or if those are exhausted. In the latter case, Venus
might end up with lakes and oceans, and rivers and springs, of strong
sulphuric acid.

Also when the temperature of Venus' atmosphere at the 73 atmosphere
level reached 31 Celsius, the carbon dioxide would form a surface of an
ocean. I expect that while small amounts of sulphuric acid can dissolve
in carbon dioxide, and small amounts would evaporate into the overlying
gas phase, sulphuric acid would not be freely miscible and would sink
to the bottom of carbon dioxide.

You can have clouds on both sides of the ocean surface, as
precipitation of liquid sulphuric acid can happen both in gaseous and
liquid carbon dioxide, but the density and viscosity of the surrounding
carbon dioxide, as well as surface tension of sulphuric acid, changes
discontinuously on the surface of carbon dioxide... And of course, you
can have critical opalescence. I wonder what precisely happens to swell
that reaches critical point...

> It ought
> to be able to cooexist with a hydrocarbon ocean, or at least certain types
> of hydrocarbon oceans, but then one has to wonder how you ended up with a
> large amount of liquid hydrocarbons in the oxidizing environment necessary
> to form oceans of H2SO4.
>
> > > Which brings up another possibility- Ammonia+CO2 / Ammonia+Hydrocarbons?
> > >
> > Ammonia and CO2 react, forming sundry compounds of limited stability,
> > like (NH4)2CO3, NH2COONH4 and curea. Which are all solid in bulk. They
> > might be somewhat soluble in liquid ammonia or CO2.
>
> Oo, I remember that being brought up as a problem with a CO2 containing
> atmosphere on an ammonia-ocean world.
> Should I expect that ammonia+CO2 would lead to the complete loss of CO2 to
> solids, (or the complete loss of ammonia, if there's more CO2 to start
> with), or, since you say they're of limited stability, would an equilibrium
> point be reached that guarantees a certain set amount of CO2 in the
> environment (either liquid or in the atmosphere), with excess getting bound
> up in solids and a deficit being replaced by the decomposition of solids?
>
> > I do not think ammonia dissolves well in hydrocarbons.
>
> So assuming ocean-forming quantities of both, then, we end up with two
> separate layers, one of ammonia and one of hydrocarbons.
>
> I wonder about the possibility of ammonia and hydrocabons reacting to form
> HCN, cyanogen, and other such things.
> Speaking of which, HCN and (CN)2 might make good thallasogens as well,
> modulo a small liquid range for (CN)2 at Earth pressures.
>
The problem is that, unlike water, ammonia enjoys much worse intrinsic
stability. And so do hydrogen cyanide and cyanogen - they are even
worse.

Incidentally, a fluid with excellent intrinsic stability is HF...

> > > > > > > or
> > > > > > > hydrocarbons floating on an ocean of SO2?
> > > > > >
> > > > > > Dubious, for similar reason. Plus, not sure about redox potential.
> > > > > > Sulphur is notoriously prone do do nasty tricks there.
> > > > >
> > > > > Am I correct in thinking that by 'nasty tricks' you mean reacting to form
> > > > > H2S and CO2?
> > > > > Hm. Liquid hydrogen sulphide might make a good thallasogen, too.
> > > > >
> > > > Not particularly good. Strong tendency to react with bases. And
> > > > relatively easily dissociated to S and hydrogen.
> > >
> > > So it needs to be put under a thick atmosphere with a cold trap.
> >
> > Compared to water, H2S is much harder to condense (boiling points +100
> > Celsius and -56 Celsius respectively). And much easier to dissociate or
> > oxidize.
>
> A very cold and/or high pressure world isn't a problem.
>
> > > Or around a
> > > star that puts out very little UV, like a non-flaring red dwarf.
> > > Or, it just needs to be on a world that's big enough to retain hydrogen
> in
> > > its atmosphere. H2S floats up, gets dissociated in the upper atmosphere,
> > > both components eventually float back down, and you get H2S again.
> >
> > Which needs strong driving force. Oxygen does not condense on Earth
> > (boiling at -183 Celsius). Whereas sulphur would precipitate as solid -
> > boiling at +444 Celsius. You would need strong heating with plentiful
> > excess of hydrogen to return to H2S.
>
> Aha. Point taken.
> OK, so H2S wouldn't make such a good thallasogen, then.
>
> > > > Mind you, there is a world with loads of free reduced S around. Io.
> > > > Does not possess dense atmosphere or oceans, though.
> > > >
> > > > Hm... S melts at 119 Celsius. With a slightly higher pressure than on
> > > > Earth, you could have a world with an ocean of hot water floating on
> > > > top of an ocean of liquid elementar sulphur. In polar regions, the
> > > > sulphur might freeze; in tropics, the water might evaporate away,
> > > > leaving bare sulphur. There would be quantities of both sulphur dioxide
> > > > and hydrogen in the gas phase above. Plus vapours of sulphur trioxide
> > > > and sulphuric acid...
> > >
> > > Oo, I like this world. Only trouble is, it would need to be very big, so as
> > > to retain hydrogen.
> >
> > Oh, double-checking probably it is not so much a problem. The reaction
> > 3S + 2H2O <-> SO2 + 2 H2S
> >
> > tends to be to the left in the normal circumstances. Heating molten
> > sulphur with water for years, with catalytic silicates available,
> > occurs in Frasch process. They do get some sulphides in the water, but
> > apparently no huge quantities of H2S.
>
> Ah, well that's good.
> On the other hand, if there is always going to be some amount of H2S in the
> air, I wonder if life on this world might never bother to evolve oxygenic
> water-based photosynthesis, seeing as how getting the hydrogen out of H2S is
> easier.
>
> > > Stephen Gillett's suggestion for how to get a world with
> > > SO2 oceans starts out similar to that, and has most of the water get
> > > dissociated, with the hydrogen lost to space, leaving behind loads of free
> > > oxygen to react with the sulphur.
> > > The hydrogen originates, I presume, from hot sulphur reacting with water
> > > vapor to form sulphur oxides?
> > Yep. Perhaps over the intermediate H2S. And as above, double-checking
> > there would probably be not much hydrogen.
> >
> > Naturally, lakes of brimstone would have to be hotter than on Earth -
> > +119 Celsius minimum. They can coexist with water if there is an
> > elevated pressure. The heat may come from the sunlight or else from
> > internal heat.
>
> Something Venus-ish, perhaps, with a thick (compared to ours, anyway)
> atmosphere of carbon dioxide causing an enormous greenhouse effect (but not
> nearly so enormous as Venus's- just enough to keep the average temperature
> above 100C). A thicker atmosphere means more even heat-distribution, though,
> which could make the idea of frozen sulphur at the poles a problem. Might
> just have to put it closer to its sun.
>
Well, Venus additionally has slow rotation - and therefore limited
Coriolis forces.

.

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