General Atmospheres type A, B and C gas mixes

[OjnoTheRed]

I'm not sure where this goes. As you might know, I am working on the T5 World Builder (link in my signature). I want to expand it to detail words using Grand Survey and Grand Census.

The particular issue is the composition of Exotic, Corrosive and Insidious atmospheres. Normally during gameplay I wouldn't worry about it - it's the effect of the atmosphere that's more important. But in detailing a world using computer software we have a chance to add a bit more colour. Note that gas mix is not the only reason an atmosphere can be rated A, B or C; temperature and pressure could be factors.

Grand Survey (following on from the original Atmospheres Special Supplement in JTAS) details the following active atmosphere components that give rise to atmospheres.

Chlorine - corrosive or insidious; in trace amounts it could be a tainted atmosphere.
Fluorine - corrosive at best;
Carbon Dioxide - a high-pressure runaway greenhouse atmosphere is what Venus has (it's > 90% CO2)
Sulfur compounds - could be a taint or pollutant, but if there are significant amounts, atmosphere could be rated corrosive or insidious because of acid-vapour content.
Methane - exotic, large cold worlds.
Ammonia - Grand Survey reckons this would be a non-irritant (hence Exotic) but if you've every smelled ammonia or read warning labels, it sure sounds like a corrosive-at-best to me, depending on concentration in the atmosphere. If it even has just enough to exist in three states like water on Earth, don't expose your skin!

I need to avoid using the Mega Traveller WBH because as I understand it, it can't be covered by the standard legal notice Marc asks for. Which is a pity, it's a great product (although I've found substantial errors - completely ignore its temperature calculations).

What other gas mixes might be out there for rocky planets for atmosphere types A, B and C? Also interested in more gaseous taints or pollutants. I want to build them into tables for detail about each world.

I've had a go with Google but we just don't know enough about exoplanet atmospheres for it to be interesting. Venus, Mars (and that's a '1' in Traveller terms), Triton and Titan - that's all we really know about. We have glimpses of others (I've read the article on Wikipedia: https://en.wikipedia.org/wiki/Extraterrestrial_atmosphere)

 

[whulorigan]

...

Chlorine - corrosive or insidious; in trace amounts it could be a tainted atmosphere.
Fluorine - corrosive at best;
Carbon Dioxide - a high-pressure runaway greenhouse atmosphere is what Venus has (it's > 90% CO2)
Sulfur compounds - could be a taint or pollutant, but if there are significant amounts, atmosphere could be rated corrosive or insidious because of acid-vapour content.
Methane - exotic, large cold worlds.
Ammonia - Grand Survey reckons this would be a non-irritant (hence Exotic) but if you've every smelled ammonia or read warning labels, it sure sounds like a corrosive-at-best to me, depending on concentration in the atmosphere. If it even has just enough to exist in three states like water on Earth, don't expose your skin!
...
What other gas mixes might be out there for rocky planets for atmosphere types A, B and C? Also interested in more gaseous taints or pollutants. I want to build them into tables for detail about each world.
...

A large world (i.e. "big world") in HZ+1 or farther might be able to retain H₂. As I recently noted in another thread, if an atmosphere is H₂ abundant, then it would be classified as an Insidious Atmosphere, as H₂ can bleed thru seals and even diffuse thru metal. (And since most environmental seals are in place to preserve at least a partial O₂ environment, the results can potentially be unfortunate should a spark or flame be introduced).

Likewise, as I recall from the Exotic Atmospheres Special Supplement from JTAS, N₂ in a typical N₂/O₂ atmosphere mix under the correct partial pressure conditions and temperatures can produce a wide variety of irritants and taints due to the formation of various nitrous-oxides (NO₃, NO₂, NO, N₂O, etc). With the right amount of H₂O vapor in the atmosphere, these can even form weak Nitric and Nitrous Acid solutions (HNO₃ & HNO₂). The wrong partial pressure of N₂ in an otherwise normal N₂/O₂ mix can potentially produce nitrogen-narcosis.

Under the right temperature and pressure conditions in an atmosphere containing H₂O, CO₂, and N₂, there might be the possibility of Cyanide Gas (HCN).

Higher partial pressure of CO₂ in an otherwise dense/normal atmosphere mix would produce respiratory problems, and might create hydrographic conditions in which the water is a carbonic acid solution (i.e. H₂CO₃ - "soda-water").

In fact, the hydrographic composition of most of the above taints, exotics, and corrosives might create interesting aqueous solutions that are not otherwise "exotic chemical fluids", but rather simply atmospheric components dissolved in H₂O.

And the Exotic Atmospheres Special Supplement from JTAS specifically noted NH₃ as at least an irritant, if not corrosive.

 

[OjnoTheRed]

Thanks heaps whulorigan - a few ideas there. I think I'll have a closer look at the original Special Supplement.

 

[Lycanorukke]

In fact, the hydrographic composition of most of the above taints, exotics, and corrosives might create interesting aqueous solutions that are not otherwise "exotic chemical fluids", but rather simply atmospheric components dissolved in H₂O.

An interesting one here on earth which could easily be classed as an exotic atmosphere even though it is a normal atmo mix is the Cave of the Crystals in Mexico - you need enviroment suits to survive because the high humidity/high temps cause the water in the air to condense inside your lungs - effectively drowning you.

If the planet is near an energetic star you could have high concentrations of ozone - which would cause you lungs as well as your equipment to rust (oxidize).

High concentrations of Noble gasses (Argon, Neon, etc) would make for an interesting light show during a storm. And a high percentage of methane could have interesting effect if a static discharge happens near a oxygen leak.

Another fun one I though about it not a gas, but fine volcanic ash. The air may be fine, but breath it in, it mixes with water in the lungs and turns into cement. Good times

 

[Timerover51]

One that I use is lack of humidity on planets with limited water. The result is that your lungs are humidifying the air you breath in, and you loose water rapidly, resulting in dehydration. I do have problems with arid worlds have enough green planets to produce an oxygen atmosphere though. I do not know if anyone has looked at what is the minimum amount of water needed to support plant life. Then there would also be a high level of particulates in the atmosphere, that would need to be blocked out with a filter mask.

Another one is an excessively high partial pressure of oxygen, which can be very damaging and deadly with long exposure. The limits what can be done at low elevations and forces the population to higher levels, where the partial pressure is lower.

While not a gas, high levels of something like mold or pollen would pose problems for individuals, and would be present in an atmosphere that is otherwise breathable.

Lastly, you can have a planet like Tarsus, with an acute axial tilt, making for extreme weather conditions over much of the planet. H. Beam Piper had a couple of examples of this is Fenris, the 4-Day Planet, and Uller, with the extreme axial tilt. Consider a planet with an axis of rotation tilted close to 90 degrees, like Uranus.

 

[whulorigan]

An interesting one here on earth which could easily be classed as an exotic atmosphere even though it is a normal atmo mix is the Cave of the Crystals in Mexico - you need enviroment suits to survive because the high humidity/high temps cause the water in the air to condense inside your lungs - effectively drowning you.

If the planet is near an energetic star you could have high concentrations of ozone - which would cause you lungs as well as your equipment to rust (oxidize).

High concentrations of Noble gasses (Argon, Neon, etc) would make for an interesting light show during a storm. And a high percentage of methane could have interesting effect if a static discharge happens near a oxygen leak.

Another fun one I though about it not a gas, but fine volcanic ash. The air may be fine, but breath it in, it mixes with water in the lungs and turns into cement. Good times

One that I use is lack of humidity on planets with limited water. The result is that your lungs are humidifying the air you breath in, and you loose water rapidly, resulting in dehydration. I do have problems with arid worlds have enough green planets to produce an oxygen atmosphere though. I do not know if anyone has looked at what is the minimum amount of water needed to support plant life. Then there would also be a high level of particulates in the atmosphere, that would need to be blocked out with a filter mask.

Another one is an excessively high partial pressure of oxygen, which can be very damaging and deadly with long exposure. The limits what can be done at low elevations and forces the population to higher levels, where the partial pressure is lower.

While not a gas, high levels of something like mold or pollen would pose problems for individuals, and would be present in an atmosphere that is otherwise breathable.

Another possibility might be a higher than normal percentage of radioactive isotopes in the atmospheric mix. This might be natural, or the result of a prior radiological event or atomic war.

 

[Enoki]

A few more:

Any range of hydrocarbons other than methane like propane, acetylene, etc.

Neon or Argon, even Radon is possible.

Bromine is another possibility. If the planet were on the hot side, it would be gaseous. Or, it might be mixed with hydrogen or in another compound. It'd be very nasty stuff.

Helium is also possible with enough gravity.

 

[kilemall]

On a more generic level, I'm interested in defining these as biosphere elements so I know what those animals and plants look like and operate on.

Different energy cycles should probably affect animal generation as much as gravity and atmo density.

 

[OjnoTheRed]

Oh, wow! Thank you all! I'm taking loads of notes here.

 

[Enoki]

I suppose it might be possible that you have a planet with an exceptionally strong magnetic field near an M type star that is just pouring out major solar flares. The combination is leaving the planet with a highly ionized atmosphere. So, most of the oxygen is in the form of mono-oxygen and ozone that are both powerful oxidants. Even if you are protected, you equipment isn't. Everything "rusts" instantly.

There might be a carbon component too that is activated carbon. It wants to bond to something, anything, and it chooses you.

At higher altitudes, the atmosphere is plasma so just getting a ship through that to land could be some serious "fun." It doesn't necessarily have to be extremely hot, but rather just all the atoms have no electrons due to the massive electrical and energy discharges going on along with all the ionized particles from the solar flares bombarding the planet's outer atmosphere.

The magnetic field however protects the surface from most of that so you are only dealing with stuff like the ozone - mono-oxygen, etc., issue there.

 

[OjnoTheRed]

Thank you all again for your replies. So much food for thought.

What I'm thinking is that where a planet has atmospheres A, B, or C I construct a table based on given temperature ranges and partial pressure ranges. Using partial pressure lets one see the effects of both high-percentage / low pressure and low-percentage / high pressure mixes. A consequence of selecting a particular gas mix (or one of the other scenarios you guys have mentioned) is a bit more detail on the exact effect on players and equipment.

 

[McPerth]

No one has yet mentioned JTAS issue #17, just dedicated to this matter?

The article about atmospheres on it gives many good examples, and I'd suggest you to use it as a basis (if you have access to it, of course).

 

[whulorigan]

No one has yet mentioned JTAS issue #17, just dedicated to this matter?

The article about atmospheres on it gives many good examples, and I'd suggest you to use it as a basis (if you have access to it, of course).

Actually that is what I was referring to in post #2: Special Supplement #2: Exotic Atmospheres in JTAS. It was an insert (I didn't remember the exact JTAS issue # off the top of my head).

 

[McPerth]

Actually that is what I was referring to in post #2: Special Supplement #2: Exotic Atmospheres in JTAS. It was an insert (I didn't remember the exact JTAS issue # off the top of my head).

Oh, sorry. I didn't identify it as such.

 

[GypsyComet]

Some good examples given so far. Note that some of them are going to be "just" a taint (Atmo 2, 4, 7, or 9) with lower concentrations, but most would turn into A-C if they were present in higher concentrations.

The one questionable mentioned is volcanic ash. A taint to be sure, as a filter mask would be needed if the air were otherwise breathable. While it might also be considered Insidious as a fine grit gets into everything and chews through seals, the best defense is actually less protection. As such, heavy ash would need to be combined with a normally dangerous gas mix to really get bad.

I've used terminator storms and condensing atmospheric changes on tidally locked worlds, on which the two halves have essentially different atmospheres, or are just carrying other things along and representing a kinetic hazard.

I've also borrowed the idea of the even higher atmospheric codes, and described worlds that were Atmo B or C at sea level but degraded to merely A at altitude.