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UWP feasibility questions

P

Piper

SOC-13
Inchin: District 268 0108 D12035C-A

I'm setting up an adventure and, for reasons of political geography, Inchin is ideally located.

I'd like to use an ice moon like Triton as a model if possible.

1. Is it even remotely plausible to have a very thin, tainted atmosphere on an ice moon without having large surface deposits of water ice? (hydro 0)

2. I'm assuming that tidal heating from the gas giant keep the core active and extensive cryovulcanism would account for the atmosphere. Is this reasonable?

3. Any ideas on how cold a planet should be before it drops from "almost breathable" to "exotic" atmosphere?

4. I'd also like some plausible reason for people to live here. I'm proposing that single-celled life has evolved here within the warmer layers (water? methane? ammonia?) closer to the core. When this organism dies, it forms layers, like coal seams that can be mined. The organic residue is used in pharmaceutical manufacture. Are there any obvious flaws with this?

Thanks in advance for any input.
 
A Triton-like model wouldn't be bad. But you do have problems.

A world that small can't hold onto an atmosphere - Triton can because it's larger, but at the same distance from the sun (30 AU) this world wouldn't be able to hold any kind of gas at all, it'd all escape into space. In fact, this world would have to be the equivalent of about 500 AU from Sol to hold onto even CO2, which is a particularly heavy atmospheric gas.

The way round that would be to have it orbit a dim M V star - at 30 AU from an M5 V at luminosity 0.0004 Sol, the temperature would be low enough (7 K - VERY cold) for it to hold onto Nitrogen at least. But that's way in the outer system for such a small star (and the equivalent of about 750-1000 AU from Sol, just to put it in perspective).

Tidal heating would allow it to generate more gas from inside itself (like Triton, though note that Triton's atmosphere wouldn't even register as Trace in Traveller). There's no way you could get a breathable atmosphere though, it'd have to be exotic - mostly nitrogen. The tidal heating could allow an ocean layer to exist inside maybe.
 
Inchin is listed as orbiting an F0-III (Yellow Giant) in the Spinward Marches Campaign, which means a LOT of luminosity, and thus solar energy, in the system. The system generation rules do allow such a star to have planets out to Orbit 16, or nearly 5000 AU. The Habitable Zone for this star is in at Orbit 6, but the system could easily have either nothing or a gravel belt in that spot, given both the propensities of Giants and the proximity to the Ancients War.

It might also be possible to tidally lock this tiny world around a gas giant (the system has 3) so that it is always in the gas giant's shadow, but it would have to be in such a distant orbit around the GG that the sun would probably be shining around the edges.

Assuming a denser planetary core might also help compensate the small size, but this world is going to be cold no matter how you slice it.
 
Oh lordy.


(a) It can't orbit an F0 III giant, they're far too young to even have terrestrial planets that have finished forming (it wouldn't even be a hundred million years old) and they're too massive and luminous to have them anyway - and

(b) you can't have planets forming that far out anyway - there's just not enough material to form them beyond at most 50-100 AU, regardless of star type.

Do yourself a favour and change the star type to an M V, it's the only way this'd remotely work. ;)
 
Thanks for the feedback.

It seems as though the surface temperature is going to shove this world firmly into the "vacc suit required" category regardless of atmosphere composition. (If a suit would even work at those temps)

Changing the UWP is an option, but I was hoping to release this publicly so I'd rather not tamper with a sacred cow. ;)

Thanks again.
 
Call Inchin a captured world with a looong orbital period. This solves several problems, including the presence of biota. The long orbital period can account for the atmospheric data, as the world is always changing.
 
Please bear with me because my understanding of planetary science is really weak.

Are you suggesting an elliptical orbit, something like (but not as extreme as) a comet?

If this is the case, and if I understand it correctly, would it work like this:

"Winter": Inchin is at the farthest approach from the primary. Atmospheric gases are locked into miles-thick ice. Radiogenic heating keeps a fluid ocean deep beneath the crust in which life can evolve.

"Summer": Point of closest approach. Stellar radiation releases atmospheric gases from the ice creating the atmosphere and trying to strip it off at the same time. Summer is "interesting" as enormous amounts of gas are released in a relatively short time.

"Spring" and "Fall": transition states from and to the iceball.

Is this on the right track?
 
Problem is that a world that small won't have much in the way of internal heating of its own, it won't have enough radiogenic isotopes in it. If there's a liquid layer then the only way to keep it liquid will be by tidal heating, so if it's not orbiting a gas giant (preferably with other moons in resonances with it) then it won't have a water layer.

Another problem is that if you want an F0 III, it seems they can only evolve from low metallicity stars, and stars massive enough to turn into these are going to be very rare indeed and probably won't have their own planets in the first place because of their low metallicity.

And for a star that luminous (about 600 Sols), an icy body (density 2000 kg/m3) that small to be able to retain even the heaviest gases would have to orbit at a distance of at least 15,000 AU - about a quarter of a lightyear! If it's rocky (density 3500 kg/m3) then that distance drops to 4000 AU, which is still way too far out (and then you have to explain where the atmosphere comes from.

That said, it's conceivable that even that small a rocky body could still be volcanically active if it's only about 300 million years old - but then you have to explain what the heck it's doing way out there. Capture is unlikely given the youth of the star, it could have been ejected into a big orbit from further insystem when the star was on its subdwarf/main sequence I guess. Its likely however that it has a very eccentric orbit that brings it a lot closer to the star, probably close enough for it to lose its volcanically generated CO2 atmosphere (and maybe even melt the surface if it gets within about 5 AU of the star)

The real problem is how anyone would even have spotted the planet at all if it's that far out. 4000 AU is vastly further than any object we can see from here in our own solar system, we'd have trouble seeing a big planet out there let alone a tiny rockball like this. And I doubt that the imperium would set up huge orbiting planetesimal finding telescopes to look for them there either.

There's just too many exceptions and coincidences going on here to make this remotely feasible IMO.
 
Originally posted by GypsyComet:
It might also be possible to tidally lock this tiny world around a gas giant (the system has 3) so that it is always in the gas giant's shadow, but it would have to be in such a distant orbit around the GG that the sun would probably be shining around the edges.
Click to expand...
I know it's moot now, but you can't actually do that either
. You can tidelock a moon so one side permanently faces the gas giant primary (like Earth's moon does here, or any of the big gas giant satellites in our solar system), but you can't lock it so that it's always hanging over the same spot (which is what happens with Pluto-Charon) - for that to happen you need the primary and satellite to have similar masses, and for the primary to not be a gas giant since they're very good at dissipating tidal forces.
 
Sounds to me like the Moon would have to be in the Gas Giant's L2 point with the sun. The L2 point is unstable, so the slightest nudge would send it careening into a new orbit. An artificial moon could maintain this position though. One way to maintain its position would be for it to shift its center of mass internally so that is cancels out all such nudges, with a handy maneuver drive in the ready should that fail.

By the way, I was rolling up a Subsector and I got this world:

------ ----------------
Hex -- NAME ----
------ ----------------
021824 LACAILLE 8760 --
Starport: Type X --------------------- No Starport. Generally a red travel zone.
Size: 0 --------------------------------- 11.6 km
Atmosphere: 0 ------------------------ Vacuum
Water Coverage: 0 ------------------- 0%
Population: 2 -------------------------- Hundreds of inhabitants.
Government: 3 ------------------------ Self-Perpetuating Oligarchy.
Law Level: 4 -------------------------- Light assault weapons (submachineguns) prohibited.
Tech Level: 1 -------------------------- Bronze Age to Middle Ages.
Non-industrial, Desert, Asteroid
Population Multiplier: 6 -------------- 600 people.
Asteroid Belts: 2 ----------------------- 3 asteroid belts including mainbelt.
Gas Giants: 2 --------------------------- Small gas giant (40,856 km), Large gas giant (61,497 km)
Star Type M0 V ------------------------ Red Main Sequence, Luminisity = 0.04, Radius = 0.549, Mass = 0.489, Habitable Zone = 0.2 A.U.
Orbital Period: 0.1279 years.

A medieval asteroid?

Explanation, a derelect asteroid generation ship that parked itself in the habitable zone of this star.
 
Originally posted by Space Cadet:
Sounds to me like the Moon would have to be in the Gas Giant's L2 point with the sun. The L2 point is unstable, so the slightest nudge would send it careening into a new orbit. An artificial moon could maintain this position though. One way to maintain its position would be for it to shift its center of mass internally so that is cancels out all such nudges, with a handy maneuver drive in the ready should that fail.
Click to expand...
As you pointed out, this would be an entirely artificial situation, and a very unstable one.

Also, the L2 point would be quite far from the planet (well beyond any natural satellite system).
 
Piper - I'm not sure if you want to reconsider your options regarding changing the star type for your universe or not, but here is why I would heartily recommend it...

The Spinward Marches Campaign is the first document that introduces star types using SCOUTS. Unfortunately, the generation of stellar types for all of the star systems in the Spinward Marches from supplement three failed to use the rules as posted. This means that Traveller - had people been more on the ball, would have had to issue errata or redo it entirely. That having been said - there is no reason why you can't redo it on your own. That is precisely what I am doing at this point for my own campaign.

Here are some of my thoughts regarding "fixing" some issues within the Traveller Universe:

1) worlds that are listed as having standard atmospheres and having a large population but a small planetary diameter are bumped up in diameter. This diameter would be the minimum required diameter that will retain an atmosphere of any kind.

2) worlds that have a standard atmosphere but zero hydrographics, have their hydrographics bumped up a bit. The reasoning behind that is that oxygen readily combines with other elements only TOO readily. In order for oxygen to be present in any breathable quantity - the world in question has to have a mechanism for replenishing said oxygen. Since water is a major requirement for producing oxygen via photosynthesis - and plants respirate (ie give off water vapor), any world in which the hydrographic value is zero yet has a breathable atmosphere is going to have to have some method for converting SOMETHING with oxygen in it to release the oxgen from its chemical bonds.
I myself don't know how much water needs to be present, but to give you an idea regarding EARTH - quoted from THE MILLENNIAL PROJECT by MARSHALL T. SAVAGE (if you don't have this book yet, buy it USED from Amazon.com - you won't regret it), page 46:

70% of the world's (earth's) biomass is alge.

Together with other alge, blue-green alge is responsible for roughly 90% of photosynthetic activity on earth.

Page 46 also tells how Blue-green alge can adapt to various hostile conditions such that it can be found in hot springs where the temperature exceeds 160 degrees, and can be found buried beneath 18 feet of frozen ice. They can even be found in lichens living in sybiosis - how's that for a simple plant? ;)

If you are interested, contact me with a private email and I can point you in a direction towards what I consider to be a good book for generating worlds for your Traveller Universe.
 
The Desert World could be dead geologically with a crust of oxides and no unoxydized materials exposed and an atmosphere of pure oxygen. The planet could be completely lifeless with no water and yet a pure oxygen atmosphere. There is nothing on this planet that would oxydize or burn, therefore nowhere for the pure oxygen to go.

Lets say the planet has a smoot crust, no mountains for instance and endless rusty plains.

How did it get this way?

A star nearby exhausted all its fuel, and the last reaction it made before going into red giant stage was a fusion reaction where its end product was oxygen, it shed its outer atmosphere upon its death and the planet accumulated an oxygen atmosphere.
 
It really doesn't work like that, Tom. When a star sheds its outer atmosphere and becomes a white dwarf chances are that (a) any rocky planets are already consumed by the red giant and (b) any atmosphere would be blown off anyway. There's no way you could get a pure oxygen atmosphere, you can't possibly produce that much oxygen that everything is oxidised and there's still room left for more in the atmosphere.

You want a planet vaguely like that, look at Mars. Its surface is largely iron oxide, the environment is strongly reducing, and the atmosphere is mostly CO2.
 
You heard about the Pulsar Planets haven't you?
The explosion of a supernova which makes a pulsar is even more violent than a simple nova that makes a white dwarf. I believe there is a certain stage in a red giant's life cycle where it sheds its outer atmosphere. A Red Giant doesn't consume all of its planets, only those that fall within its radius. Some outer planets will never the less survive the red giant stage as they are too far away to be swallowed by the star's radius. Stars of a certain type will produce oxygen in their cores by fusing other elements together, once its fule runs out and the star is not massive enough to fuse elements heavier than oxygen, its core will collapses into a while dwarf while heating up the outer atmosphere and causing it to expand into a planetary nebula as its called.

Is it not possible than some planetary nebulas around certain stars will be made primarily of oxygen as that star will have fused most of the lighter elements leaving just oxygen when its nuclear fule is exhausted?

Some of the remaining planets in the system would then accumulate much of this oxygen from the expanding planetary nebula. If the planet was an ice ball for instance, the oxygen would settle around the planet and find nothing to oxydize, it can't oxydize ice, for example. It it settled on a gas giant, it would oxydize they hydrogen, if enough oxygen is provided, it might oxydize all the hydrogen and turn it into a water giant.

So I take it, you don't think there is any free oxygen gas clouds floating around in space?
 
Don't get me wrong. I'm just having some fun playing Devil's advocate, in most cases an oxygen atmosphere indicates the presence of life, or at least water. What I'm trying to do is imagine a circumstance where an oxygen atmosphere can appear in the absense of water or life. I believe Mercury has a trace atmosphere of free oxygen, it is effectively a vacuum, but it is more substantial than anything around the Moon.

Getting back to my above scenario, after the red giant sheds its atmosphere, there would be much debris left over in the Solar System, this is a situation similar to the early star formation period. Planets in the outer solar system which may have escaped the red giant's expansion, may be dragged inward toward the White Dwarf. If the circumstances are right, some smaller ice balls may be dragged inward and become water planets if chance brings them the right distance from the White Dwarf. Gravity would pull in alot of gaseous oxygen that would settle on top of the watery core. If enough oxygen were to settle on top of the ocean, the planet might turn into a gas giant of a very unusual type, one with a thick oxygen atmosphere with some water clouds. At a certain altitude if the distance form the white dwarf is right, the atmosphere would be breathable
 
Is it not possible than some planetary nebulas around certain stars will be made primarily of oxygen as that star will have fused most of the lighter elements leaving just oxygen when its nuclear fule is exhausted?
Click to expand...
No, because most stars don't stop fusing when they hit oxygen - they stop when they hit carbon, then they shed their outer layers and become WDs. Bigger stars carry on but go all the way to Iron and then explode as supernovae.

And like I said, planets would have all their atmospheres blown away when the star sheds its outer layers (and they probably wouldn't have atmospheres to start with since the temperatures would be higher while the star was a red giant, which means that they can't hold onto the gases). If any planets survive they MIGHT be able to capture some gases floating around the system but it'd be a mixture of elements, not pure oxygen and it'd be a tenuous atmosphere at best.

You can get free oxygen in some ways that don't involve life - either through sputtering or photolysis. Sputtering occurs when hard radiation hits a planets' surface. if the surface is icy, then that breaks up the H2O molecules into its components - the H2 floats off but the heavier oxygen can remain. Ganymede and Europa have extremely tenuous O2 atmospheres as a result of this process, but it's not going to be enough to create a THICK O2 atmosphere (particularly since that same radiation also doesn't allow the O2 hang around those satellites).

Photolysis could work in some cases. Panthalassics are huge terrestrial worlds that are basically an earth-mass or two of rock with an earth-mass or two of water on top. They have so much water on them that photolysis (which is basically the same sputtering, but acting on gases instead of a hard surface) breaks up the H2O vapour in the atmosphere. Given there's so much H2O in the atmosphere of these planets - and that the planets are so massive - the oxygen remains and can build up over time. This would allow you to have SOME oxygen in the atmosphere where you don't necessarily have life to produce it. But you need a hell of a lot of water in the atmosphere to do this.

But there's no case that I can see where you can get a thick, pure oxygen atmosphere.
 
A carbon core world would be quite unusual though, or at least we haven't seen such in out own Solar System. A Red Giant could leave enough carbon behind to make plenty of planets out of.

What would a carbon core world do to the economics of the OTU? A carbon core world could be much bigger than Earth while retaining an Earthlike gravity, and if you dig down into a carbon core world, you would eventually hit a layer of diamond. Carbon core worlds are flammable, so you probably won't find an atmosphere containing much oxygen. If you could cover over the carbon core with silicates, you could insulate a habitable atmosphere from the carbon core, and it would make a nice artificial world with plenty of living space. Carbon core worlds would probably make diamonds dirt cheap.
 
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