Venus vs Mars vs Titan

samy · 2006-10-13 15:34:43

It seems to me that there are three primary destinations being considered for colonization in the long term: Venus cloudtops, Mars and Titan. Each of these has lengthy threads about each one *individually*, but I couldn't find a thread for comparing and contrasting the three options. So I thought I'd try one. I'm by no means a specialist, so I'm sure there'll be lots of correcting for you guys to do.

I decided to count out any possibilities of significant matter transfer between planets. In other words, "living off the land". Shipping bars of nitrogen between planets might be realistic 200 years in the future, but it's science fiction now. I picked the following criteria to compare by.

Pressure
Temperature
Energy
Hydrogen (needed for water)
Carbon (needed for organic life)
Oxygen (needed for water and breathing)
Nitrogen (needed for buffer gas)

Going from low to high AU

VENUS CLOUDTOPS

Pressure: Good (1 bar - Earth level)
Temperature: Good (0-50 Celsius - Earth level)
Energy: Good (solar and geothermal prospects good)
Hydrogen: Bad (None)
Carbon: Good (more than enough!)
Oxygen: Good (more than enough!)
Nitrogen: Good (more than enough)

MARS

Pressure: Bad (~1 kPa = 1% of Earth = near vacuum for human purposes)
Temperature: Good to bad (up to 20C in ideal situations, down to -140C in worst case scenario)
Energy: Bad (low on chemical and geothermal, mostly solar energy)
Hydrogen: Bad (some in polar water ice but is that sufficient amounts for colonization?)
Carbon: Bad (some in atmosphere, but insufficient for long-term?)
Oxygen: Bad (some in atmosphere, but insufficient?)
Nitrogen: Bad (none?)

TITAN

Pressure: Good (1.5 bar = Earth 5m underwater pressure = adaptable to humans)
Temperature: Bad (-180C = coldest of these three options)
Energy: Good (chemical-based)
Hydrogen: Good (expected to be plentiful in the form of hydrocarbons and water ice)
Carbon: Good (hydrocarbons)
Oxygen: Unknown (water ice expected but unconfirmed, amounts are big question mark)
Nitrogen: Good (98.4% of atmosphere is N)

Based on these quick and dirty reviews, I'm collating what would be needed as survival measures on each planet.

VENUS CLOUDTOPS

Needed: Hydrogen

MARS

Needed: Pressure regulation, temperature regulation, hydrogen, carbon, oxygen, nitrogen

TITAN

Needed: Temperature regulation, perhaps oxygen?

----

Conclusion:

Most places will require imported materials. Titan is the closest to importation independence, especially if water ice is found in large amounts to allow full-scale oxygen production. Venus is also close, but the lack of hydrogen severely hurts survival prospects. Mars is the worst off; it does have carbon, oxygen and hydrogen, but the amounts of all three are much lower than on our other two candidates.

As for active stationkeeping measures, Venus is the best off, as it requires neither pressure or temperature regulation as long as altitude is kept relatively steady. Titan is next best off, only requiring temperature regulation, but pressure is not an issue on Titan. On Mars, again, the worst of the three, both pressure and temperature regulation is critical.

Comments on where I'm wrong?

karov · 2006-10-22 13:09:44

Venus - hydrogen = in the H2SO4 clouds. More than enough in case of closed hydrosystem...

samy · 2006-10-23 01:51:24

All the hard data I've managed to find says H2SO4 is only to be found in trace amounts. If you can find a source that says there's actual substantial amounts of H2SO4, I'd like you to point me to that source.

I imagine the amount of H2SO4 might be barely enough for a couple of manned stations, with a lot of collecting work, but not much more than that. Can you cite any actual amounts?

Here's Wikipedia's atmospheric composition:

Atmospheric characteristics
Atmospheric pressure 	9.2 MPa
Carbon dioxide 	~96.5%
Nitrogen 	~3.5%
Sulfur dioxide 	.015%
Argon 	.007%
Water vapor 	.002%
Carbon monoxide 	.0017%
Helium 	.0012%
Neon 	.0007%
Carbonyl sulfide
Hydrogen chloride
Hydrogen fluoride 	trace

Doesn't even mention H2SO4, so it's presumably less than all the above elements. That's not very much now is it? Sure, there's *some* hydrogen present, but I'm skeptical about there being useful amounts.

Let's note that there is even more actual *water vapor* H2O than there is H2SO4. If we need water, it would make sense to me to go to the water vapor first because it is more plentiful. You don't try to squeeze water from a stone while you're standing next to a lake.

Anybody want to do the math for how many liters of water is 0.002% of Venus' atmosphere?

karov · 2006-10-23 02:44:20

http://en.wikipedia.org/wiki/H2SO4

The H2SO4 forms above the Venusian atmosphere from the water and the SO2 so from the data you provide -- simply these "trace amounts" of water are in forms of water AND sulphur acid. In atmosphere this is the situation - the hydrogen is locked in H2O and H2SO4 -- of course you use the water directly - harvesting it from the atmosphere via condensation... From H2SO4 you dissociate it thermally or/ and electrically using the abundant venusian cloudtop solar energy ( two ddirectional = totally about 4 kW/m2 harvestable ...) drop the SO2 and confine the water into the habitat...

Very easy to calculate the "moisture" in the cloudtop. ( Note: no water deep into the atmosphere caue the heat pushes it higher ):

The total mass of the venusian atmosphere is:

http://www.spds.nasa.gov/planetary/fact … sfact.html

480 000 000 000 000 000 000 kg

multiplied by 0.00002 ( only the water figure relevant cause the H2SO4 fits into the same amount recombining and dissociating ... )

= 9 600 000 000 000 000 kg. totally or roughly 10 000 cubical kilometers of water

about half the amount of water of

[/url]http://en.wikipedia.org/wiki/Lake_Baikal the largest single liquid fresh water r … driest air

karov · 2006-10-23 04:23:13

Venus:
~ 10 trillions of tonnes / m3 of water available on Venus ( putting asside the mantle water, which regarding the ~3% solar nebula estimated initial water content, should make at least 5 to 10 earth`s hydrospheres-worth under the venusian crust as it is here on Earth, Mars, etc... but it is too hard = expensive for utilization... AND putting asside the super-plenty of hydrogen and everything very nearby - the Sun itslef, cause to star-mine we need more mature technology for plasma manipulation... ) in its atmosphere...

Lets provide each human colonist with total of luxurious 1000 m3 per person ( in all sences per capita, and envisioning multiple hi-tech use: parks, lakes, riverlets, industrial and biospheric use - irigation, washing, industrial solutions, streets washing, swimming pools, plenty of cheap water, which circulates time and again forwver in onee ENCAPSULATED , closed circle of fully tamed hydrosphere -- evaporating and condensing, purified by rough distilation methods... etc. etc. )

Than water-wise Venus cloudtops could harbour about 10 billion people.

When we are talking about "lets colonize the V. cloudtop!" -- often is envisioned flimsy fleet ot fragile aerostats... ships and cities at most...

... rather I`d see a configuration of floating ( just by the lifting force / buoyancy of the breathable atmosphere inside ) huge islands , archipelagoes of country- or state-size united walking surfaces = linear dimensions of dozens and hundreds of miles, privided with solar-power pannels from above and from underneath...

the atmosphere contains all the neecessary building material - carbon, nitrogen, water. It is much easier to go down to the hot solid surface to mine rocks and metals, using combination of tank-like excavation tech + aerostats, than to dig too much rock.
The huge almost continent size rafts provide enough landing area for laser-thermal rocket engines "burning" CO2 as reaction mass, with the plenty of solar energy provided -- the lack of enough planetary axial rotation dooming the implementation of synchronised orbital towers is thus in a large degree compensated.
The enormous rafts also give us the opportunity to apply long mas-drives tunnels for exporting VEEERY precious carbon, nitrogen, oxigen for the rotating colonies in the solar-orbital vicinity and the entire inner SolSys.

All this eventuality, driven by SRS / self-replicating systems -- ENTIRELY "of-the-land" or more exact "living-of-the-air" in this case , un-manned untill sufficient shirt-sleeve human habitation capacity is created.

Cause the usefull EM solar radiation on the Venusian cloudtop is 4 times more abundant than on the Earth ( due to the fact of almost complete reflection from the clouds ) -- the walking area of the habitats could be on several floors / levels separated several dozens of meters from eachother. The rafts could be anchored with elevator towers down to the solid surface for the high-temperature mining equipment... The temperature is only ~300 degrees celsius and the pressure only 40-50 bars at the mountain-tops -- conditions which our technology handles already for centuries = steam ngines, normal kitchen ovens...

Give to these 10 bln. colonists the much normal and used-to population density of say 100 persons per km2. ( like France, Spain, Austria...) -- ~ 10exp8 km2

Arrange the rafts to be 4 leveled , so on each square meter of habitat / walking area to correspond the earth`s solar constant of about 1 kW/m2.

The above 10 times USA habitat area divided on four = ~25 mln. km2 divided on the 4.6x10exp8 km2 of the entire Venusian surface area ( distregsarding the fact that 60 km higher of the center gives us bigger area ....) ... these 10 bln. people will be housed on CLOUD-CONTINENTS covering less than 6% of the total venusian surface.

Take this:
http://en.wikipedia.org/wiki/Anglosphere ( decreasing the water per capita with 30% ), scatter the several hundred states, provinces, etc. accross the venusian globe`s cloudtop ( don`t forget to link the rafts with air=hovering tunnels / vacuumed for super-fast maglev transport )
and here we are with one decent and stylish mode of Venusian colonization...

The eneergy per capita available will be qual to the earth` solar constant for 50 km2 per person ( counting in night and day side insolation ) = 50 GigaWatts per human unit pays easy any aircon bills.

samy · 2006-10-23 11:16:28

I'm a little skeptical about the prospects of extracting water from the atmosphere when it's such a small percentage -- can you tell me more about these US military efforts of water extraction that you referred to?

Also, if we *can* extract 100% of the water vapor and put it to use as liquid water, that would also prevent the H2SO4 from forming, thus preventing any acid problems too, right?

Your ideas for continent-sized colonies aren't feasible in the near future. Maybe 500-1000 years from now, but for the moment, if we're going to go there in the next 100-200 years, I think we will have to do with these "flimsy aerostats", so don't be so dismissive of them. Everything must have a beginning.

SpaceNut · 2006-10-23 11:35:45

I'm a little skeptical about the prospects of extracting water from the atmosphere when it's such a small percentage -- can you tell me more about these US military efforts of water extraction that you referred to?
Also, if we *can* extract 100% of the water vapor and put it to use as liquid water, that would also prevent the H2SO4 from forming, thus preventing any acid problems too, right?

Air2Water technology

Couple this with
Air Stripping

Also just reheat in glass container to reevaporate just the water to be recondensed leaving the solid in the glass container.

samy · 2006-10-23 11:41:33

I couldn't find anything on the Air2Water page regarding how much moisture the air must have for the tech to work. It speaks of "humid air", which suggests to me there must be significant (more than 0.02%) amount of water vapor in the air.

SpaceNut · 2006-10-23 18:58:50

Not to be rude but before I answer Samy, first a few questions I am sorry if I offend.

Why have you come to visit the NewMars site and to pose such an interesting topic for discusion?

What do you expect to contribute and or how will NewMars contribute to your needs?

From the Air2Water Dolphin:
It’ll produce 20 liters of water a day in 70% humidity, which is about the amount that comes in one of those fat-ass 5 gallon bottles, but without the waste or transportation emissions.

From a much older article: Refreshing Drinks of Fresh Air

Even in the parched Mesopotamian desert, the air holds plenty of water. The trick is getting it out. Machines have been around for years that can cool the air down to the point where water droplets will condense like dew beading on an oak leaf. But they're energy hogs, using almost 650 watt-hours just to get a single quart of H20. The goal of Darpa's Water Harvesting program is to extract that water without using up so much power.

Even the act of using a compressor will end up with about a gallon or so from running all day.

samy · 2006-10-23 19:17:23

Why have you come to visit the NewMars site and to pose such an interesting topic for discusion? What do you expect to contribute and or how will NewMars contribute to your needs?

Hello SpaceNut! I hope this tangent won't take up much of this thread as I (and I suspect others) come here to talk about space, not about myself.

I come here because I am interested in off-Earth colonization and would like to learn all I can about the difficulties inherent therein. It is only through knowing those difficulties and understanding them that we can hope to overcome them. It is my hope that before I die, I will get to see (by video transmission) humans living and working on aerostats on Venus. Though I understand of course with the current pace of space exploration I'll likely die before that happens. I hope to contribute by asking questions where I don't know things and providing information where I do know things. NewMars serves my needs by allowing me to get in touch with other people who are interested in the same kinds of things as I am. You can't just go around discussing terraforming with one's office mates whose main interests are beer and sports.

I hope that satisfies your curiosity about me. Now, on to the topic here!

From the Air2Water Dolphin:
It’ll produce 20 liters of water a day in 70% humidity
Even in the parched Mesopotamian desert, the air holds plenty of water. The trick is getting it out.

Venus is much less than 70% humidity, of course. So will Air2Water be of any use there?

What is the approximate humidity of the Mesopotamian desert? I suspect it is on the order of 1-5%, though that is merely a guess. In any case I suspect (though I'll gladly be proven wrong) that even the driest Earth deserts are orders of magnitude different from Venusian humidity (or rather, dryness) levels. In absolute amounts, of course, Venus has a lot of hydrogen as karov calculated, but as noted in that quote, "the trick is getting it out" and I am honestly skeptical about squeezing water out of 0.02% humidity air, at least at any kind of reasonable speed. Let's not forget that to get the amount of water that karov projected, we will need to process *the entire Venusian atmosphere*, which is a long-term project if ever I saw one.

SpaceNut · 2006-10-23 19:46:49

Thanks for answering the curiosity.
I am a SpaceNut as my wife would put it. I read everything that I can. I am not a scientist only an average joe who loves seeing rocket launched, seeing the many images from probes or satelites and dreaming of the day that I can go too.

The principal of the unit is to lower the temperature of compressed air thus concentrating the amount of water vapor.
On venus that would be Sulfuric Acid of which to get it to give up the water can be done a couple of ways.

nickname · 2006-10-24 05:19:21

Living in a pressure cooker, cold vacuum or liquid nitrogen bottle.
None of those sound very appealing, do we have a fourth choice? planet Hawaii?

Venus cloud top has its possibilities, but sulphuric acid and any balloon material don't mix well.
A balloon failure means a quick one way trip to the surface.
Getting what we need for existence in the atmosphere of Venus probably isn't to difficult with the abundant solar energy and atmospheric compounds.

Mars probably has all the resources we need just below the surface, in fact most of what we need in the atmosphere.
A good air compressor, vapor extractor and well heated structure are the check list for Mars.
If we set up home near the poles we probably wouldn't need a vapor extractor, we could just go collect ice.
Solar power won't be much use on mars, so a nuclear power probably would be needed.

Titan would require nuclear power just to settle on the surface, without constant heat everything will shatter like glass.
Carbon steel on the surface would be as fragile as cheap glass, water ice as tough as carbon steel.
Any attempt to live on Titan will require large quantities of power with many backup systems.
Titan probably has all the compounds we need for existence also.

karov · 2006-10-24 11:55:55

Just to note that on Venus all the water is between 50 and 60 km hight , where it is in form of thiny droplets of water+H2SO4 mixture -- DROPS means condensed -- with ~1atmosphere and ~300K roughly "livingroom conditions" it is:
-- easy to estimate the local water %-tage from the condensation point for that pressure/temperature
-- the total volume of this concentric cloud shell which contains ALL the hydrogen... no water deep at the surface ...

It occurs that all the water is close bellow to the cloudtop, and if forming CLOUDS at earth-like temperature/pressure -- it should be much-much more humid than Iraq.

samy · 2006-10-24 12:04:51

"Should be". I hope you're right, as that would indeed make things much easier.

I'm hoping Venus Express will be able to shed some more light on the Venusian atmosphere composition. When the hell do we get some actual results out of it anyway? It's been there half a year dammit!

Thanks nickname, for a great rundown on the comparisons. I'd hoped to focus on comparing and contrasting the broad strokes of the top three choices, rather than get bogged down on the details of any one in specific -- not too much, anyway: some discussion must of course be conducted.

karov · 2006-11-13 14:11:27

"Should be". I hope you're right, as that would indeed make things much easier.

"should be" is in this case just figure of speach Don`t hope - easier and faster, read:

http://en.wikipedia.org/wiki/Dewpoint

http://en.wikipedia.org/wiki/Relative_humidity

"...For a given dewpoint and its corresponding absolute humidity, the relative humidity will change inversely, albeit nonlinearly, with the temperature. This is because the partial pressure of water increases with temperature – the operative principle behind everything from hair dryers to dehumidifiers. ..."

http://en.wikipedia.org/wiki/Absolute_humidity

http://en.wikipedia.org/wiki/Cloud

===================================================

Venus cloudtop = at least 2-3% water

samy · 2006-11-22 01:38:17

the partial pressure of water increases with temperature

So most of the water on Venus can be found at the lowest altitudes, since that's where the temperature is highest? That's too bad, I would've hoped for more humidity at the cloudtop levels.

nickname · 2006-11-22 06:27:36

samy,

I believe that model for Venus is incorrect or not exactly correct.

Water in any form can only exist so far down on Venus.
The temperature near the surface is to hot for even steam to exist, also the convection on Venus is very different than on earth.

Although the humidity will be higher further down, it will also be the driest nearer the surface due the temperature.

That throws a monkey wrench into predicting where the highest concentration of water will be.

Venus might be ultra dry from the surface up to some altitude, then very humid slowly decreasing with altitude.

karov · 2006-11-23 15:26:59

I think that most of the venusian water is within the clouds... drier bellow and above --- I`ll search for more proofs. The logic behind this notion of mine is that condensation occurs...

nickname · 2006-11-24 04:28:41

karov,

Almost a guarantee that most of the moisture is in the clouds.
Probably not far below the clouds is the no moisture zone.

Just above the clouds nothing to hold onto moisture for long.
Venus probably has a very weird water migration system within its clouds.
I wouldn't be surprised if short fall rain converted to steam as it drops was possible on Venus.
I believe i remember reading that Earth has less water in its cloud system at any given time than Venus has all the time.

karov · 2006-11-24 12:52:50

nickname,

thats exactly what I think. that the shortlived water/H2SO4 drops evaporate very close under the clouds... That means practically the whole water / hydrogen reserve of Venus is situated just bellow the "habitable zone" = cloudtop , and thus very well situated for harvesting and sequestration into the floating habitats "water and sewage utility system"...
====================

Can you find this source about the cloud systems comparison Earth-Venus?

karov · 2006-11-24 13:14:46

TITAN
Pressure: Good (1.5 bar = Earth 5m underwater pressure = adaptable to humans)
Temperature: Bad (-180C = coldest of these three options)
Energy: Good (chemical-based)
Hydrogen: Good (expected to be plentiful in the form of hydrocarbons and water ice)
Carbon: Good (hydrocarbons)
Oxygen: Unknown (water ice expected but unconfirmed, amounts are big question mark)
Nitrogen: Good (98.4% of atmosphere is N)

TITAN
Needed: Temperature regulation, perhaps oxygen?
----
Comments on where I'm wrong?

pressure: perfect. no need for pressure transition.

temperature: just splendid -- easy to store LOX, liquid methane... outback "naked" superconductors, deeeeep heat sink for thermal machines -- internal combustion ones, nuclear... such temperature makes rheological miracles with quite humble earthly materials -- under ~80-100 K the water turns into crystal as hard as quartz...

energy: for good or bad -- ENTIRELLY imported. chemical energy is usefull and convenient, but the oxidizer must be imported. The natural nuclear fissible materials should be quite deep underground into the rocky core -- unfortunatelly the icy worlds differentiate chemically from the gravitation too efficiently. Titan would be depleted from heavy elements. but Titan itself only -- plenty of all the Periodic table content around in the Saturnian system into the less or no-differentiated small moonlets and ringlets. The primary energy to move a Titanian civilization would be: gravitational -- extracted from the orbital mechanics of the Saturnian system directly or via the saturn`s mag-field... and solar -- 1% of the earth level is still abundant with good concentration methods. The solar panels / lenses / mirrors will be with only 10 times bigger linear dimensions than at Earth... The primary saturnian energy-carrier will be the Oxigen... easy to store and trasport it in LOX form. On Titan LOX would be like petrol -- just pour it in and out of tanks and pipes... A chemical rocket / made of more than steel strong plastic running on naturally liquid methane and LOX would have great performance for the whole system of saturnm and beyond. The saturnian escape velocity from Titan is only 7-8 km/s --- far better than Earth delta-V environment leading to far more interesting and rich spots...

hydrogen: not necessary to use it free -- super-plenty of water and hydrocarbons

carbon: plenty.

nitrogen: plenty

oxygen: FOR GOD SAKE the entire "planet" of Titan is made of water-ice "rock". the same way the Earth of silicate ones...

Titan indeed could export massive quantities of all the CHON materials, in goods or as resource , without the depletion to become noticeable for multi-millennia...

Needed: ice igloo and "volcano" ice tubes = i.e. protected areas, terraformed within -- I`m talking about kilometers and dozens of kilometers of open seesights lines... and in them and only in them temperature control... Using directly outer / outback air : just filter out the methane, add 210 milibars of O2, warm up and voila! ...
oxygen is everywhere -- tap the kinethic and potential grsavitational energy of the system... capture enough sunlight...

G.K.

karov · 2006-11-25 03:43:12

MARS

Pressure: Bad (~1 kPa = 1% of Earth = near vacuum for human purposes)
Temperature: Good to bad (up to 20C in ideal situations, down to -140C in worst case scenario)
Energy: Bad (low on chemical and geothermal, mostly solar energy)
Hydrogen: Bad (some in polar water ice but is that sufficient amounts for colonization?)
Carbon: Bad (some in atmosphere, but insufficient for long-term?)
Oxygen: Bad (some in atmosphere, but insufficient?)
Nitrogen: Bad (none?)

The solar energy on Mars is quite abundant, actually Mars is within the habitable / goldylock zone of the Sun. Local optical amplification available... VERY important energywise is the phase transition of the CO2 seasonally -- that could be used for CO2-steam engines --- just tap the co2 fountains which erupt every polar day/summer -- couple the streams with turbines , produce electricity -- use it to crack electrochemically the present there water ice, regolith, etc. to extract the necessary and plenty elements... The amounmt of co2 which undegoes annually phase shift from solid to gas and vice versa -- drives as much energy as thewhole power supply in USA... The energy density in the vapour pressure of co2 sealed in a bag or tank in dry ice form at -120 / -140 degrees celsium and released when solar heated at +40 / +50 degrees celsium is entire 1/125th of the gasoline/oxygen...
Overall all the volatiles CHON are insufficient quantativelly, but the defficiency could be "re-filled" from the Outer system... NO PROBLEM that during the re-fill on the planetary surface could be deployed meanwhile massive engineer works and massive presence of humans and technics -- just choose the landing sites, the "shells" diameters, etc. Judging from the meteoroids crashing all the time into the Earths atmosphere -- the lesser than 10 meters ones burst in the kilotone range in to the stratosphere -- ice particles "catapulted" into Mars-landing course from the Outer system ( the Jupiter trojans, the Neptune trojans, Centaurs, KBOs...) with diameters of less than 1 meter will do no harm to the surface works... BTW, ice chuncks of this size could be launched into collission course really using rotational catapults -- the KBO orbital velocities which should be canceled to allow the "shell" to take course falluing into the Inner system, is just in order of about 1000 m/s .. a catapult with very short arms will works well, the power of the catapults, may come from mechanical energy of the multiple binaries out there ( there are multiple binaries cause the spaces are bigger and the Hill spheres hold well even for very little objects ). So, with technology from the Stone age - ropes, cables, catapults, bolo... Mars could be poured with as much CHON as necessary... The impact velocities would be lowered so accumulation effect to occur -- the impacts would bring heat into the atmosphere , too...
If the ices-catapult system is life-like , i.e. replicator -- it can start with miniscule investment and to produce result limited only by the needs in this case. ( in total limited only by the amount of mechanical gradient out there and the overall mass present... )

Although, we can pass without the catapult bombardment ... Mars local energy and chemicals resources are more than abundant for massive collonization, and even terraforming if most of the territory is left barren and arid high mountain desert with only 10-15% river / lake... oasis zones.

nickname · 2006-11-25 04:11:47

karov,

This link is pretty good for the sulphuric acid rain cycle on venus.

http://www.zoomschool.com/subjects/astr … here.shtml

Wish i could find the article about h20 content in earths atmosphere Vs Venus.
Still looking though.

samy · 2006-11-25 09:19:30

I hope Venus Express will get us more hard data on Venusian water vapor, among other things!

karov · 2006-11-26 03:17:23

karov,

This link is pretty good for the sulphuric acid rain cycle on venus.
http://www.zoomschool.com/subjects/astr … here.shtml
Wish i could find the article about h20 content in earths atmosphere Vs Venus.
Still looking though.

thanx nickname. It seems that the scarce water, or more corect the hydrogen of the venusian atmosphere is concentrated between 16 and ~60 km altitude. Thus the deep and the high atmosphere are dry. This would ease the task for water harvesting for the needs of cloudtop colonization...

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