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Is this an impossible situation? (Long Post)


Hi, all,

I need someone with more knowledge than me (which is to say: anyone!) to help out with the creation of a new alien species. More for the satisfaction of my own curiosity than any pressing in-game need.

I'm not looking for an absolute hard-science answer, just looking for something within the bounds of plausibility.

I created MTU using the Galactic 2.4 program, as I really like its alternate UWP generation system. In addition to the standard UWP stats, the alternate system also generates three UWP extensions: Life, Resource level, and Exports. As I'm not using the official alien races for my game, I decided to use Galactic's Life stat as a guideline to determine where to place my aliens. In addition to swiping aliens from other games (2300 AD especially), I also decided that it would be fun to create a new race from the bottom up using the GURPS 4e Space book for guidance.

The subsector that will form the initial campaign area has one system - Polassar - that supports a sentient, non-spacefaring race. The UWP for Polassar's main world is:

UWP B Trade Codes Z PBG
--------- - -------------- - ---
CADA336-8 Fl Lo Ni Wa A 900

Plugging this into the continuation system from LBB6 yielded the following system:

P....Polassar - K3 V
8B...Ammeni - M6 D

The main world was placed outside the star's habitable zone because it's too big to be there going by the rules in the book. Since the population of this planet was to be entirely composed of aliens, it didn't bother me to place it in the outer zone.

Calculating everything out yielded the following data for the stars and main world (I think I got it all right):

Stellar Data (Polassar)
Bolometric Magnitude 6.72
Stellar Luminosity 0.624
Effective Temperature 4420
Stellar Radius 0.7028
Stellar Mass 0.672

Stellar Data (Ammeni)
Bolometric Magnitude 15.9
Stellar Luminosity 0.00003
Effective Temperature 2700
Stellar Radius 0.006
Stellar Mass 1.11

Orbital Data
Orbital Distance 1 AU
Orbital Period 1.22 years (445.56 days)

Planetary Data
World Volume 1.953
World Mass 1.953
Surface Area 1.250
Escape Velocity 13.73
Cloudiness 100%
Albedo 0.7
Greenhouse Effect +15%
Local Temperature 114.6874 (-158.463C / -253.33 F)
Summer Temperature 153.6812 (-119.469C / -183.044 F)
Winter Temperature 86.01558 (-187.134C / -304.842 F)
Axial Tilt 20

So we have a big, frigid world completely covered by a fluid ocean. The atmosphere is too dense at sea level to support (Earth-like?) life, but the upper atmosphere is breathable.


1. Is there any compound that remains liquid at such temperatures (-190 to -110 C)? My limited research finds that elements with low melting points also have very low boiling points.

2. Assuming there is some fluid that fits the above, would it be able to support life in the high pressure zone at sea level?

3. If no life can exist at sea level, I suppose we could have weird towering rock spires that allow for life in the upper atmosphere. What would such life look like?

4. Should I just regenerate the system? K-class stars just don't pump out all that much heat!

Looking at GURPS Space, it seems that hydrogen-based life is most probable for this world, but the temperatures might be too low?

Thanks for reading this ramble, and thanks in advance for any guidance.
The formulas in Book 6 don't do a good job of modeling the atmospheric greenhouse effects of thicker atmospheres very well. It is possible, that with such an extremely dense atmosphere (think Venus), that at the surface, temperatures might be more tolerable. Probably not liquid water, but maybe only -50 degrees or so.

I read a short story WAY back in high school about a world with an atmosphere that was so thick that it sort of merged into the ocean. There wasn't really a clear distinction between liquid and gas at the "surface".

Not sure of the chemistry that would work in that type of atmosphere either, but Methane/Ammonia might be possible. It would also probably be more likely than Hydrogen.
Pressure isn't actually a problem; life forms could develope that were adapted to the high pressure. Interesting things might happen to them if they entered a "Standard" pressure atmosphere or pressurized human vessel, but they'd be fine at home.

Water. Yes, water can be liquid at extremes of cold, esp. under high pressure. Those temps push the limit, but there are other ways to keep it liquid. Thermal vents under the ocean, high salinity (Or other solute), and lots of tectonic activity and fast currents could all combine in varying ratios to keep water liquid beneath (Most likely) a cover of ice in most locations.

More trouble comes from life developing on a planet that cold. It's pretty unlikely to develope into anything more complex than bacteriums, microbes, lichens, and the like. Unless you can somehow make an arguement for higher temperatures below sea, you may want to consider regenerating the system, or tweaking it a little at the very least.

Holy crap. I think I just actually used stuff I learned back in college when I took a class in Xenobiology...
Just occured to me that maybe I should explain WHY complex higher life is unlikely to develope in this situation:

A lack of stellar radiation, the most readily available source of energy for most biomass production, limits the amount of low-level producers, thus limiting how high an ecology can really go. Extremes of cold also tend to inhibit biological activity (Which is why we freeze food to store it), and while we only have our own earth biology to go by, all evidence points to most biological processes requiring at least some warmth to be active, if not to stay alive at all. Plenty of life can survive extreme cold, but few things actively respirate, metabolize, and/or reproduce at those temperatures.
That was fast. Thanks for the tips, guys!

@Plankowner: A slight increase in temp. due to pressure had occurred to me, but I wasn't sure if its effect would be greater than the greenhouse effect given in LBB6. That's good info. I also like the idea of the atmo merging with the ocean.

@Archhealer: Thanks for the information on keeping the liquids...well, liquid! The world's temperature is the bugbear here. Looks like some tweaking is in order; maybe a hotter primary, or see what effect a hotter companion might have.

(edit: and thanks for the follow-up post, too)

Any more information or guidance would be great!
Can't answer in depth right now, but briefly - we need to know the surface pressure of the planet. Dense, High implies that it's higher pressure at the surface than earth's, but what makes it a D instead of an 8 is that the oxygen pressure is too high to be breathable safely by humans.

Higher pressure means that water can stay liquid at higher temperatures, but unless the pressure is REALLY high it won't affect the freezing point much. However, denser atmospheres have higher greenhouse effects, so that might actually raise the temperature a lot more than implied by the books. (Venus' 90 atm CO2 atmosphere basically has a greenhouse effect multiplier of +150% IIRC).

So basically I suspect the temperature at the surface of the planet should be higher than what the CT formulae say it should be.
Ah, I'll plug a higher greenhouse value into the spreadsheet and see what that does.

Thanks, Malenfant!

btw, I actually used ideas from your revised stellar generation table for this exercise (mostly to eliminate the large number of K-class stars that seemed to pop up...not that that happened here), so more thanks to you!
Remeber that the greenhouse effect partly depends on pressure... did you get a pressure value generated for the planet? It's not listed in your initial post. That would tell us a lot anyway. IF the GFX is high enough to keep water liquid on the surface (under those pressures) then you may just have a water ocean there.

As for the stars, you *should* be getting a large number of K V stars, they're the next most common type after M V (IIRC it's something like 70% are M V and 15% are K V?). I don't think my RSGTs do much to eliminate the K Vs...

I'm glad the tables are useful anyway
If no life can exist at sea level, I suppose we could have weird towering rock spires that allow for life in the upper atmosphere. What would such life look like?
My guess would be avian life-forms would do better in the higher mountains, crags, spires, cliffs, high plateaus, etc. Ground-level dwellers are out of the picture, since you mentioned that sea level would be too inhospitable. Just my 2 Solomani centavos.
@Malenfant: Unfortunately, no pressure values. I left my full notes home, but I'm pretty sure there's no pressure value formula in book 6. I could be wrong, however; I just started using the detailed system tables this weekend.

And mea culpa on the statement about K-class star frequency (my ignorance knows no bounds). I have to look at your tables again, but I'm pretty sure it had something to do with inconvenient stars being generated using the continuation system and its modifiers. Your tables made G-class stars a bit more common when genning systems for highly habitable UWPs, I think.

In any event, they ARE useful!

@Maladominus: avian forms would be great, but there is very little land on the planet (hydro A), so no mountain ranges. I like the idea of big spires of rock or crystal just sticking outta the ocean, though. Perhaps the dense lower atmo might even be able to provide support for certain very small, light creatures with a large surface area...I need to do more research.

You guys are all fantastic.

Traveller: Showing the Limitations of Higher Education in the Humanities
There aren't pressure tables in CT, IIRC they first showed up in DGP's World Builders Handbook for MT. Personally I use a range of values from 2.5 to 100 atmospheres for Dense, High atmospheres (they're basically Very Dense N2/O2 atmospheres).

With no land, I'd guess that any avian life is probably going to be living on the wing, landing in the ocean to rest, and probably birthing live young there too.
Originally posted by Malenfant:
With no land, I'd guess that any avian life is probably going to be living on the wing, landing in the ocean to rest, and probably birthing live young there too.
Avian life could use hydrogen gas bags to go airborne with a secondary gas bag of methane (a product from it's digestive tract) to use a a propellent in a orifice similar to a pulse jet engine.

The avian could also be a amphiban, laying eggs in water to be fertilized, the young live the first part there, similar to a fish. After eating alot, growing it develops into the adult avian form. Might transform in a coccoon of some sort.

My question is what will the avian eat? Probably small flying insects that quickly grow on the floating dead bodies of near surface dwelling fish, etc. In a way similar to maggots for flies but much quicker.

A few species of avian animals might feed on other smaller avians. Think a hawk.

Just my $0.02
I just realized that if the pressure is high enough, you could have gas-baloon creatures that just 'float' effortlessly by bouyancy. Especially if the atmo has an odd gas mix, like high levels of hydrogen, methan, or helium. They could fill their air bladders with it to float.
Damn, I check in just before leaving the office and these great ideas make me wish I was home already!

Gas balloons...I hadn't thought of that. I was thinking of creatures that sort of float on heavy air currents, lightweight creatures with wide surface areas something like leaves.

But...neat. You guys have roughed out an entire ecosystem!

I will be playing around with this stuff tonight and post results. I'm thinking I can derive a figure for pressure from the GURPS book.

I love these boards.
Pressure looks to be about 9 atmospheres, if I'm using the book correctly.

GURPS4e Space gives the formula for Atmospheric Pressure as:

Pressure = Atmospheric Mass x Pressure Factor x Surface Gravity

Atmospheric Mass was randomly generated according to the book to be 1.5

Pressure Factor is 5, for Large, non-Greenhouse world.

Surface Gravity is 1.2G.

What would that do to the Greenhouse Effect, if anything?
Just running the star stats through my spreadsheets... you want to change Ammenni to a M6 V rather than a DM - otherwise you've got a white dwarf out there which would have roasted your planets when it was a red giant (this is one of the things my RSGTs got rid of, maybe that's what you were thinking of?).

I figure a world density of 5350 kg/m3 (assuming a radius of 8045 km), that sound right? (0.97x earth density), escape velocity of 13.912 km/s, gravity of 1.2267g, blackbody temperature of 247.67K...

hm, and a MMW of 3.17. Which means it can't hold onto hydrogen but it can hold onto helium. Maybe that's why its atmosphere is so thick (that said, helium's a light gas, you'd need a lot of it to increase the pressure)?

Now, I'm using the greenhouse effect calculation from GT: First In in my spreadsheet, which does seem to break down at high pressures (i.e. pressures much over 1 or 2 atms). BUT... if I put a pressure of 5 atms in then the greenhouse effect is 0.611, and coupled with the albedo of 0.7 that means you get a final temperature of 294.66K, which is nice and warm and allows liquid water to exist on the surface.

Coming up with an atmospheric composition is a bit arm-wavy, but if I put in 40% Helium, 40% N2, 13% O2, 5% H2O and 2% CO2 then that gives me a relative molecular mass for the atmosphere of 18.74. That means that the scale height for the atmosphere is about 11 km, so at a height of 10 km the pressure is 1.65 atms which means the oxygen pressure at that altitude is perfect for human life (0.2145 O2 ATA) - but of course there's no mountains at that altitude anyway, so it's kinda moot. At the surface though there's far too much oxygen for humans to survive long-term (O2 ATA is 0.65) and I suspect they might have some other effects from nitrogen narcosis at that pressure.

Boiling point of pure water at the sea level is going to be 152.14C (452.14K), freezing point is going to be about 273K still (it's actually a fraction of a degree lower than at earth's sea level). Salts obviously change that appropriately.

Anyway, you might be able to have your liquid water world if you use this setup, though someone who knows a bit more than me about atmospheres might want a look at the composition to see if it's reasonable.

As a bonus, the planet won't be tidelocked to the star, which means it can have a moon. Taking some random numbers, if it was formed with a 12 hour rotation period, then it'll take 58 billion years for it to tidelock to the star (longer than the age of the universe, which is 13.7 billion years)! If your system is middleaged (say, 6 billion years?) then it's current rotation period due to stellar tides would have slowed from 12 hours to 13.362 hours. If there's a large moon, that could have slowed it down more though. That age also gives you long enough to have some complex life evolving on the surface. And the star being a K V, its luminosity hasn't changed significantly over the planet's lifetime either.
Just saw your last post... I'm not familiar with GURPS Space 4e, but can you tweak the pressure down to 5 atms? If I put in a value of 9 atms then your greenhouse effect is 1.101 and your surface temperature is 384.1K, which is way too hot (but then the FIrst IN GFX equation is breaking down at this point, methinks. Problem is, I've not found a realistic way to calculate it, even in the science literature).

A 5 atm surface pressure seems to give you the results you're after anyway...
D'oh! My star generation spreadsheet seems to be using the LBB6 companion table. I put it together at 2AM on Saturday after a few Guinness...I will change the companion star. Thanks for the catch.

And...wow...thanks for all that info! This will be a huge help. It looks like this will allow for a few different possibilities for the chemical basis of life on the planet.

I can definitely tweak the pressure down to 5 atms. Reviewing my figures and comparing with yours, I see a bit of variance, which probably means I'm mis-reading something in Space (very likely), and probably means my figure of 9 atms is off somewhere. Just adjusting a couple dice rolls brings it down to 7.2. I'll go over my calculations, add a bit of the Fiat Factor and I think that'll work out fine!

Again, thanks for putting this together! I will be working on the aliens tonight.

I am in your debt, sir!
Yer welcome

Also, all the options that people have thrown about for life on the planet could of course exist all at once ;) .
Originally posted by Archhealer:
I just realized that if the pressure is high enough, you could have gas-baloon creatures that just 'float' effortlessly by bouyancy. Especially if the atmo has an odd gas mix, like high levels of hydrogen, methan, or helium. They could fill their air bladders with it to float.
I assume that the pressure is "high enough".

Traveller has always postulated that avian life forms will thrive in DENSE or STANDARD atmospheres. They will have a hard time existing or flying in thinner atmospheres.

According to Ken's description of this world, I imagine a world with an overall dense (very dense) atmosphere, and high pressures (crushing pressures at sea level).

Also, the concepts of aeroplankton and "air whales" (i.e. gas-bag whales) has been explored in at least a couple of official Traveller published worlds. All of these are good ideas worth considering.