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NorthernDevo
2016-Aug-26, 12:06 AM
Hello folks; here is a very quick and extraordinarily weird question about Venus. As many know I'm writing a S-F mystery novel which takes place on the surface of Venus, and I'm just trying to flesh it out a little.

We know that Venus's surface temperature is higher (460deg.C) than the melting point of lead (327deg. C). We also know lead is present in Venus's crust, though I haven't been able to find an exact breakdown of the metallurgy. (I saw it before; darned if I can find it again.)

Here's the question, and like I said it's weird: is there any possibility at all there could be liquid running creeks/rivers/ponds of lead and/or other liquid metals running free on Venus's surface?

I suspect not, the Universe simply isn't that weird. Or rather, it is; I'm constantly astounded at the wonderful weirdness of the Universe. But it couldn't possibly be so delightfully strange as having a babbling, running brook of lead on Venus. I'm unsure however of why: is there not enough lead concentrated near the surface? Is it all bound up in sulfides? I don't know.

But you gotta admit: How cool would it be to be standing there in Venerian night beside a glooping, oozing and glowing red-hot creek of melted lead? Hollywood effects designers would just drool! I'm sure it couldn't actually happen but it would be nice. :)

Thanks!

CJSF
2016-Aug-26, 02:58 AM
I probably know less than you, but I suspect the high pressures do all sorts of weird things, chemically, to the elements present on the surface.

CJSF

chornedsnorkack
2016-Aug-26, 04:25 AM
The mountains of Venus are, for some reason, reflective.

Solfe
2016-Aug-26, 05:44 AM
Snow? (https://en.wikipedia.org/wiki/Venus_snow)

I guess it's a thing on Venus. It's a wiki link to Venus Snow, no apparent relation to Miike Snow.

Swift
2016-Aug-26, 02:22 PM
Another to keep in mind: the properties of sodium, for example, are not the same as the properties of sodium chloride. Just because there is lead in Venus' crust, doesn't mean that it is in the form of metallic lead (molten or not). The melting point of lead (II) oxide, PbO, is 888C, for example.

Squink
2016-Aug-27, 01:56 AM
Melting point is low enough, 327.5C, but boiling point is 1749 C (https://en.wikipedia.org/wiki/Lead). That's way above anything you'll find on Venus, so Pb vapor pressure will be quite low.
No lead rain, so no lead streams, it's all going to have oozed it's way to the low spots over the last few thousand millenia.
Perhaps some lead ponds with basalt bottoms at the poles?

NorthernDevo
2016-Aug-27, 05:16 AM
Right; I hadn't thought about the boiling point until later. My hope was that lead could, in some way, act the way water does on Earth but that certainly couldn't happen on Venus. Also while I knew much of the lead would be bound up in sulfides, I was hoping some might remain in pure form. For no reason other than pure coolness, of course.

Ok; so that looks like a good answer; no real possibility of liquid flowing on the surface. Too bad in one way; I'm kind of relieved in another because I don't have to write it and try to make it not look cheesy! LOL

Still...well, you've left a possibility for one Evil Bubbling Cauldron of Infernal Nastiness...sweet! :D

chornedsnorkack
2016-Aug-27, 05:37 AM
The boiling point of lead is 1749 degrees, but the boiling point of lead sulphide is 1281 degrees - which is what allows lead sulphide to condense on mountains of Venus.
But is only lead sulphide stable on Venus? Or both lead and lead sulphide?

NorthernDevo
2016-Aug-27, 08:24 AM
I'm sure I saw something about that but CJSF is right; lead is an element, can it survive in a pure state? Would it matter?

chornedsnorkack
2016-Aug-27, 08:49 AM
I'm sure I saw something about that but CJSF is right; lead is an element, can it survive in a pure state?
Lead can even exist on Earth:
http://www.mindat.org/min-2358.html

NorthernDevo
2016-Aug-27, 01:06 PM
Yes, but I didn't ask the question very well. I meant to ask if lead could exist in a pure state on Venus. Pressure is 93 times Earth, atmosphere is CO2 with contaminants at 460 degrees. As far as I know lead is quite reactive so as far as I can see it wouldn't exist in pure form. I wouldn't have thought to consider that without your guys' help so thanks again! :)

Solfe
2016-Aug-27, 03:06 PM
Stupid, tangential question. NorthernDevo mentioned the surface conditions. Does this state radically change the underground conditions from what we know on Earth and in what way? I wouldn't expect to see limestone and stuff, but would there be Hawaiian type basalt everywhere or is more like the ocean basalts?

chornedsnorkack
2016-Aug-27, 03:58 PM
Yes, but I didn't ask the question very well. I meant to ask if lead could exist in a pure state on Venus. Pressure is 93 times Earth, atmosphere is CO2 with contaminants at 460 degrees. As far as I know lead is quite reactive so as far as I can see it wouldn't exist in pure form.

Lead is reactive with, for example, oxygen - and there is less oxygen on Venus than on Earth.

NorthernDevo
2016-Aug-28, 12:51 AM
Lead is reactive with, for example, oxygen - and there is less oxygen on Venus than on Earth.

Well...yes. :confused-default: In fact there is no free oxygen on Venus. But oxygen is not the only element lead can react with. Far from it - while I do not for a moment pretend to understand the chemistry, from my reading lead seems to be quite a feisty element; happily partying with any number of other elements to create compounds, salts and sulfides. And in the pressure-cooker environment of Venus, it would happen much faster than it ever could on Earth.

chornedsnorkack
2016-Aug-28, 06:42 AM
And the sublimation of lead sulphide on Venus implies that lead sulphide does form on Venus. Sure.
But is galenite the only stable form of lead on Venus?

cjameshuff
2016-Aug-28, 12:59 PM
Melting point is low enough, 327.5C, but boiling point is 1749 C (https://en.wikipedia.org/wiki/Lead). That's way above anything you'll find on Venus, so Pb vapor pressure will be quite low.
No lead rain, so no lead streams, it's all going to have oozed it's way to the low spots over the last few thousand millenia.
Perhaps some lead ponds with basalt bottoms at the poles?

Probably no exposed bodies: lead is heavier than pretty much any sort of rock, so all the rocks, gravel, sand, and dust would float on it.



Lead is reactive with, for example, oxygen - and there is less oxygen on Venus than on Earth.

There's a couple orders of magnitude more oxygen in the atmosphere of Venus than on Earth, and the planet itself is about 1/3 oxygen, just like Earth. Lead just needs to be more reactive than whatever the oxygen in its surroundings is bound up with...it may well reduce CO2 to CO, for example.

chornedsnorkack
2016-Aug-28, 01:19 PM
Lead just needs to be more reactive than whatever the oxygen in its surroundings is bound up with...it may well reduce CO2 to CO, for example.

Which it does not do.
On Earth, lead sulphide is stable in depths, but not on surface. On surface, lead sulphate oxidizes, like:
PbS+2O2->PbSO4

On Venus, you might have reactions like
PbS+2SO3<->Pb+3SO2

cjameshuff
2016-Aug-28, 02:11 PM
Which it does not do.

You're going to have to do more than just assert so.

chornedsnorkack
2016-Aug-28, 02:45 PM
You're going to have to do more than just assert so.

Starting with standard enthalpies of formation:
PbO: -219,4 kJ/mol (Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. )
CO2: -393,5 kJ/mol
CO: -110,5 kJ/mol

So, the reaction:
PbO+CO->Pb+CO2
is exothermic and goes to the right.

dgavin
2016-Aug-29, 01:52 PM
Venus has an rather acidic atmosphere. That may over time, break down various metals allowing them to be picked up as vapor, they may then recrystallize later as a sort of metalized rain.

NorthernDevo
2016-Aug-30, 04:23 AM
Starting with standard enthalpies of formation:
PbO: -219,4 kJ/mol (Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. )
CO2: -393,5 kJ/mol
CO: -110,5 kJ/mol

So, the reaction:
PbO+CO->Pb+CO2
is exothermic and goes to the right.

:scope: Wow....did that ever go way over my head!

I love this forum for all the things I learn on it, but a little explanation for the non-University guy over here would be greatly appreciated. :)

chornedsnorkack
2016-Aug-30, 08:20 PM
To say briefly: lead is "quite" reactive, but not that reactive compared to some other metals, like iron.
In Earth atmosphere, with surplus free oxygen, lead corrodes - slowly.
On Venus, with the lack of free oxygen, it is not clear to me that lead would corrode. Heat promotes corrosion, but also the other directions of reactions - what matters is the position of equilibrium. The atmosphere of Venus might operate like a smelting furnace for lead.

NorthernDevo
2016-Aug-31, 03:49 AM
Ok, great; thanks - that's an answer I understand and can build my understanding on. The question that immediately pops to mind is this: while looking up lead on Venus, the one compound that keeps coming up is lead sulfide; I can't find reference to pure lead anywhere. It appears most frequently - as mentioned above - in the reflective 'snow' coating the Venerian highgrounds. While I understand that O2 is a major catalyst (and again not pretending to understand the chemistry) it seems to me that lead does not need oxygen to become bound up in sulfides. There are other catalysts it can use. I might be reading the formula wrong, but it looks to me like it can also use sulfur dioxide as a catalyst; and does to create galena. My question is of course if that is wrong, if it is where is it wrong and does lead positively need free oxygen to be bound into a compound?

I realize this is high-school level chemistry but I failed that course. I'm much better at creative writing and history. :D

Thanks again. :)

Swift
2016-Aug-31, 01:27 PM
My question is of course if that is wrong, if it is where is it wrong and does lead positively need free oxygen to be bound into a compound?

I'm not completely following all this, such as the comments about "catalysts" (I suspect you may be using that term incorrectly), but there is one part that is clear: lead does not need free oxygen to be bound into a compound. If one took lead metal and sulfur and reacted them in an oxygen free vacuum, you could make lead sulfide. I even suspect that there may be pathways to make lead into lead oxide without free oxygen, but I'm not expert enough in lead chemistry, nor feel up for a big researching of the topic.

I actually suspect that detailed chemistry at conditions typical for the surface of Venus have not been studied, and that there are probably surprises that will eventually be found, but not anytime soon.

NorthernDevo
2016-Aug-31, 04:42 PM
(Chuckle) I'm almost certainly using the term 'catalyst' incorrectly though at the moment I thought it was right. I meant that as far as I know lead doesn't need free oxygen to form a compound, which leads to my confusion about why free oxygen is being concentrated on above.

chornedsnorkack
2016-Aug-31, 08:43 PM
If there is a surplus of free oxygen, lead is readily oxidized, to compounds. This is what happens on "roasting" of sulphide ores in Earth furnaces:
2PbS+3O2->2PbO+2SO2
In Earth atmosphere, the resulting lead oxide has to be reduced in next step with carbon monoxide.
If there is a surplus of free sulphur, galena is stable and lead oxide would be reduced:
2PbO+3S->2PbS+SO2
But on Venus, there is neither free oxygen nor a surplus of free sulphur. The atmosphere of Venus contains modest amounts of SO2 and COS.
So I wondered whether the surface of Venus might have the conditions for a reaction like
2PbO+PbS->3Pb+SO2