Fluid Oceans - Am I Missing Something?

[J Harper]

I’ll admit that my scientific knowledge is not the greatest, so I may be missing something that’s obvious to others.

My players may go to a fluid ocean world in Chant in the future. I’m researching what water alternatives I could use for the planet.

Per world creation in the core rules, atmospheres that generate fluid oceans trend hot. However, common water substitutes, such as ammonia, become gases at very low temperatures, usually below 0 degrees Fahrenheit.

Explain to me as if I was a small, slow child what I am missing?

 

[Vormaerin]

Most of the expected fluid oceans should be in cold planets so you have methane or ammonia, as you suggested.

But there are high temperature options. Sulfur does weird things at high temperatures with variable fluidity and viscosity at different temperatures above the boiling point of water. A particularly carbon rich planet could have effectively liquid tar. Or your ocean could be molten rock. At high pressures, the oceans could be supercritical fluids like carbon dioxide.

I'm not a scientist either, but keep in mind that pressure affects boiling point. Water boils at higher temps on a dense atmosphere world and at lower temps on a thin atmosphere world. This is true of other substances as well.

 

[Condottiere]

Probably other factors are involved than just fluid dynamics.

As I understand it, our oceans act as heat sinks; on the other hand, once temperature hits a certain threshold, accelerates the greenhouse effect.

 

[fvcoulter]

Don't forget to factor in water's strange behavior when it transitions from liquid to solid. Most liquid to solid transitions involve becoming denser. Water is weird in that the solid form would float on the liquid form. I don't think that's true for the other liquid oceans.

 

[Baldo]

A particularly carbon rich planet could have effectively liquid tar.

An excellent example is Xuan Nu, the worldbook is HERE.

 

[Marc]

Probably other factors are involved than just fluid dynamics.
As I understand it, our oceans act as heat sinks; on the other hand, once temperature hits a certain threshold, accelerates the greenhouse effect.

Where you talk about oceans and the greenhouse effect, you are also introducing variables like "Albedo".
As an example, water oceans freeze and gather a snow covering. Because of that, the dark blue and green of the oceans (which would absorb light) turns white and reflects the light.

Then, there are the questions of ice caps?
Terra has had a good relationship between our ice caps and oceans until recently. As ice caps melt into the ocean, they cool the lower depths.
But, if they melt off, that cooling effect will die off the heat sink can well turn into a steam pot.

 

[ottarrus]

I’ll admit that my scientific knowledge is not the greatest, so I may be missing something that’s obvious to others.

My players may go to a fluid ocean world in Chant in the future. I’m researching what water alternatives I could use for the planet.

Per world creation in the core rules, atmospheres that generate fluid oceans trend hot. However, common water substitutes, such as ammonia, become gases at very low temperatures, usually below 0 degrees Fahrenheit.

Explain to me as if I was a small, slow child what I am missing?

It's the properties of the possible fluids.
Ammonia, for example, goes to a liquid state in very cold temperatures, so an ammonia sea would need to be cold.
Each molecule will have a different liquid state temperature and therefore each water substitute that makes up the 'ocean' will have a differing liquid temperature. Hydrochloric acid [a classic Traveller 'corrosive atmosphere' hydrosphere] will have a different temp than ammonia [another classic].

Look for the JTAS articles on 'Exotic Atmosphere' and that will help.

 

[fvcoulter]

Where you talk about oceans and the greenhouse effect, you are also introducing variables like "Albedo".
As an example, water oceans freeze and gather a snow covering. Because of that, the dark blue and green of the oceans (which would absorb light) turns white and reflects the light.

Then, there are the questions of ice caps?
Terra has had a good relationship between our ice caps and oceans until recently. As ice caps melt into the ocean, they cool the lower depths.
But, if they melt off, that cooling effect will die off the heat sink can well turn into a steam pot.

I question that "good relationship [...] until recently" statement. Basically, the Earth has had two stable climates. First, the frozen ice ball. Second, the ice free planet. The current case, which is part of an ice age without massive ice caps, tends to be unstable.

 

[Marc]

I question that "good relationship [...] until recently" statement. Basically, the Earth has had two stable climates. First, the frozen ice ball. Second, the ice free planet. The current case, which is part of an ice age without massive ice caps, tends to be unstable.

Actually, the one "constant" is change.
That said, neither the Ice Ball or All Water Terra were stable.
The ice ball repressed energy until it burst forth and forced change.
The ocean earth enforced an albedo which increased stored energy until change was, again, enforced.

Granted, we are ~30 to 50k years of of hard ice age at the moment, but there appeared to have been a balance until Humanitii broke it.
Now, the glaciers which were our world's air conditioning system have been seriously degraded and the average temperature year on year is rising.

While we "hope" we can find ways to arrest this, it may be as good as wiping a window dry in the middle of a downpour.
The models are interesting, but still theoretical.

We shall see what happens.