Planet Atmospheres/Oceans?

[lordmuffin]

When I was making a planet for _Augustus_'s new PF:CE Revived, I was contemplating planet atmospheres and oceans. I was wondering if a planet could have an atmosphere of dry ice crystals, and maybe oceans of liquid nitrogen.

What do you guys think? What are some crazy atmosphere and ocean combinations that you can think of? What is possible?

[lajoswinkler]

Dry ice crystals, no. That's a powdered solid suspended by nothing, therefore it will fall on the ground just like any matter does in vacuum.

Oceans of liquid nitrogen? Let's look at the phase diagram.

With sufficiently high gravity to hold enough gaseous nitrogen to exert pressure on the phase boundary, and with a temperature low enough, yes - liquid nitrogen can be stable, and I don't see any reason why we couldn't have such place. Nitrogen is extremely abundant. It is possible Triton is vomiting liquid nitrogen which quickly turns to gas because of vacuum. If Titan was further away, its hydrocarbons would solidify, and nitrogen would create oceans.

[jfull]

I think liquid nitrogen requires significant pressure as well as low temperature to remain liquid. Otherwise it will just boil off as nitrogen gas.

at very low temperatures an normal pressures it will become solid nitrogen ice.

[jfull]

There could still be a significant amount of dry ice crystals carried by the wind though.

Mars has tons and tons of dust that remains suspended in the air for a long time

[Kryten]

A liquid nitrogen ocean would also include other 'ices' that are liquid at that sort of range-methane, CO, et.c.

[AngelLestat]

venus has also co2 ice crystals at 80 to 100 km height.

[lajoswinkler]

There could still be a significant amount of dry ice crystals carried by the wind though.

Mars has tons and tons of dust that remains suspended in the air for a long time

That was not his question. He asked about an "atmosphere" made of dry ice crystals. That is impossible. The only way for powder to be suspended in vacuum is electric force, but the source of it is stellar radiation, high flux of which is nonexistent at distances where CO₂ can exist in solid phase.

Regarding the liquid nitrogen ocean, I've posted the phase diagram. Such oceans are possible on somewhat larger bodies, away from their stars.

Edited December 24, 2014 by lajoswinkler

[Armchair Rocket Scientist]

When I was making a planet for _Augustus_'s new PF:CE Revived, I was contemplating planet atmospheres and oceans. I was wondering if a planet could have an atmosphere of dry ice crystals, and maybe oceans of liquid nitrogen.

What do you guys think? What are some crazy atmosphere and ocean combinations that you can think of? What is possible?

As mentioned, an atmosphere made entirely of solid crystals will NOT work.

As for liquid nitrogen: yep, it can exist in lakes or oceans, and it's fairly common. An object the size of Titan can hold onto gaseous nitrogen at 70 Kelvins (the middle of Nitrogen's liquid range) without problems. However, the planet would likely have nitrogen oceans in equilibrium with a mostly nitrogen atmosphere; most of the substances common enough to form planetary atmospheres freeze at a higher temperature than nitrogen boils. The main exceptions are hydrogen and helium. Assuming a density similar to Pluto, a planet about half Earth's mass will retain helium at 70 K, and a planet of Earth's mass or larger will retain hydrogen. However, there are two main obstacles to the formation of nitrogen oceans.

1. Nitrogen isn't THAT common. All the nitrogen in Earth's atmosphere is only enough to form a layer about 10 meters deep if evenly distributed over the entire surface. Venus has several times more nitrogen than Earth, enough to form a 46 meter layer. By comparison, Earth's oceans would have a depth of 2500 meters if evenly distributed, and Venus's CO2 would form a 900 meter layer. As result, nitrogen will more likely form shallow lakes like Titan's than real oceans.

2. Nitrogen has a narrow liquid range of 14 *C at Earth's atmospheric pressure, compared to 100 *C for water and 21 *C for methane. This means that small seasonal temperature swings can cause a planet's oceans to freeze or boil. This is made worse by the fact that planets could enough to have liquid nitrogen on their surfaces will also have very long years (about 60 years for a sunlike star), and shallow nitrogen lakes will have far, far less "thermal inertia" than Earth's oceans. However, a thick hydrogen and/or helium atmosphere could stabilize the oceans; a pressure of 20 bars or higher will give nitrogen a liquid range over 50 *C.

[lordmuffin]

Another question: What about atmospheres with crystals of asbestos, or some other crystalline thing?

[lajoswinkler]

Another question: What about atmospheres with crystals of asbestos, or some other crystalline thing?

Formation of asbestos requires hydration, so it would have to be a world with previously accessible water, at least underground. Then most probably eolic errosion of such rocks to detach its fibrous needles and form tiny fibrous particles. Two things would need to cease forever: water rain to avoid dissolving them, and tectonic movement to avoid recycling of the crust.

Then you need decent stellar radiation to ionize the dry, vacuum surface of such world and to suspend such dust by electric force.

It's a series of not improbable events. I'm quite positive there are many world where such "atmospheres" (where "atmo" is not applicable) exist at least as transient phenomena. The Moon has it, although not made of asbestos.

[jwenting]

Regarding the liquid nitrogen ocean, I've posted the phase diagram. Such oceans are possible on somewhat larger bodies, away from their stars.

of course the temperature range at which they are stable is exceedingly narrow, effectively precluding any kind of weather patterns...

[YNM]

Atmosphere of crystals isn't a daydream - Earth does have it. Just remember that everything is in equilibrium - ie. Water vapour exist with water droplets, water ice exist with snow or ice ground. Granted that carbon dioxide is more extreme so you need to get some views on the temp and the pressure first.

[kerbiloid]

Tmelt, K Tboil, K

Hydrogen 14 20

Oxygen 55 90

Nitrogen 63 77

Methane 90 111

Ammonia 195 240

Earth athmosphere = Nitrogen, Oxygen, some Water and CarbonDioxide.

Earth ocean = Water + CarbonDioxide (~140 times more than in athmosphere) + salts.

Nitrogen is the remain of original ammonia, splitted to N and H by solar radiation and chemical processes.

H has dissipated in space, N we still have in atmosphere.

Oxygen has been extracted from CarbonDioxide by algae photosynthesis.

Water and CarbonDioxide are condensed volcanic gases, have been and still is being released from the depths due to geological material draining.

Salts are original alcaline metals rocks dissolved by Water while it was being thrown out by volcanoes, condensed and replenishing the oceans.

So, looks like:

Originally we have:

Resources

- a layer of condensed ammonia+methane slosh on the planet surface.

- water and carbonates inside the planet material.

Energy:

- heat from Sun (depends on Sun distance and luminosity)

- UV from Sun (depends on Sun distance and luminosity)

- heat from depth (depends on planet mass)

- maybe heat from a giant planet (as Jupiter and Io) - infrared heat and/or tidal deformation heat.

The warmer and closer Sun or the closer a giant planet - the warmer the surface.

The bigger the planet - the warmer the surface.

Ammonia+methane slosh partially melts, partially sublimates.

An ocean appears: Methane + some dissolved Ammonia.

An atmosphere appears: Methane + Ammonia.

The warmer and closer Sun - the more often ammonia and water are being splitted by UV to nitrogen, oxygen and hydrogen (the latter one quickly dissipates in the space).

Ammonia slosh → Nitrogen + Hydrogen (being lost)

Ammonia gas → Nitrogen + Hydrogen (being lost)

Atmosphere gets consisted of Nitrogen + Ammonia pollution.

Ocean stays Methane + Ammonia pollution.

Surface layer stays methane+ammonia+some water slosh.

So, we get Titan.

If it's cold, all stays the same until Sun extends and it gets hot.

If it's already enough hot: all ammmonia and methane slosh gets vaporized.

Methane dissipates, ammonia splits, we have no more ocean or slosh, but a pure nitrogen atmosphere above the rocky surface.

We can see an early Earth-like planet.

If the planet is small and has no significant geological activity, it will just loose all its methane and ammonia dissipated.

We get a typical asteroid - a rock without an atmosphere or an ocean.

The bigger the planet - the larger quantities of water and carbon dioxide is being thrown from depths into atmosphere.

If the planet is very hot (enough close to Sun), both gases stay gases. No ocean appears.

We get a thick and dense Nitrogen + Water + CarbonDioxide atmosphere.

As both Water and CarbonDioxide are "greenhouse gases", we get a neverlasting greenhouse effect.

Water gets splitted by UV → Oxygen + Hydrogen. All three hot and lightweight gases - O, H, N - dissipate in space.

We get a dense pure CarbonDioxide atmosphere with neverlasting greenhouse effect - i.e. Venus.

If the planet is not very hot, volcanic Water vapour gets condensed and forms a water ocean.

It dissolves soluble rock material (alcaline metal salts) and gets salty.

As CarbonDioxide is highly soluble in Water, almost all amount of Carbon dissolves in the appeared ocean, reacts with solved alcalines and gets stored a carbonate/hydrocarbonate ions mixture.

Now we get: Nitrogen + CarbonDioxide atmosphere and muddy and salty Water ocean, i.e. Proterozoic Earth.

When algae appear they convert atmospheric CarbonDioxide into Oxygen and precipitate insoluble salts floating in ocean.

We get a Nitrogen+Oxygen atmosphere and lucent salty Water ocean, i.e present-day Earth.

So, we can see several main compositions, and we can freeze or heat them.

A. Ammonia+Methane slosh layer. If enough warm - some Methane atmosphere and Methane ocean. (Maybe "Pluto").

- Freeze: nothing changes.

- Heat: all melt, vaporize and dissipate in space. First we get methane ocean and methane atmosphere, then - no ocean, no atmosphere.

B. Nitrogen atmosphere. Methane ocean. Ammonia+Methane slosh layer. ("Titan").

- Freeze: Ammonia+Methane slosh permeated with frozen Nitrogen.

- Heat: almost the same as in "A" case.

C. Nitrogen atmosphere. No ocean. Rocky surface. ("Pre-Archaean Earth")

- Freeze: An unstable equilibrium of solid, liquid and gaseous Nitrogen. Then - a thin nitrogen slosh covering all over the surface.

- Heat: dissipating Nitrogen atmosphere, then nothing.

D. Nitrogen+Water+CarbonDioxide atmosphere. Very hot, no ocean. Rocky surface. ("Volcanic age Earth").

- Freeze: Nitrogen+CarbonDixode atmosphere, Water ocean. Then Nitrogen atmosphere above thick Water + CarbonDioxide ice layer. Then just a thick Water + CarbonDioxide ice layer, smeared with Nitrogen slosh.

- Heat: "Venus".

E. Dense and hot CarbonDioxide atmosphere with neverlasting greenhouse effect. ("Venus").

- Freeze: CarbonDioxide atmosphere above CarbonDioxide ice layer. Then - thick CarbonDioxide ice layer.

- Heat: just CarbonDioxide leak until no atmosphere or ocean on a rocky surface.

F. Nitrogen+CarbonDioxide atmosphere. Salty Water ocean. Rocky dry land surface. ("Proterozoic Earth")

- Freeze: The same as "D".

- Heat: The same as "D".

G. Nitrogen+Oxygen atmosphere. Water ocean. Soil-covered rocky dry land surface. ("Present-Days Earth")

- Freeze: Nitrogen+Oxygene+CarbonDioxide atmosphere above Water ice layer. Then - Nitrogen+Oxygene atmosphere above Water ice layer, smeared with CarbonDioxide slosh. Then - no atmosphere above Water ice layer smeared with slosh.

- Heat: Dense Water+Nitrogen+Oxygen atmophere, no ocean, greenhouse effect. Then - leaky Nitrogen+Oxygen+Water atmosphere above rocky surface. Then no atmosphere.

So, possible combinations look such way:

Solid layer over rocks:

Ocean:

Atmosphere:

Conditions (temperature, etc):

1. "Asteroid".

- Solid: None. Maybe - a dust layer of frozen methane, ammonia or nitrogen.

- Ocean: None.

- Atmo.: None.

- Cond.: Any.

- Remark: Also a frozen "Pre-Archaean Earth".

2. "Pluto (?)"

- Solid: Ammonia+Methane.

- Ocean: Maybe methane.

- Atmo.: Maybe methane.

- Cond.: Very cold.

3. "Titan".

- Solid: Ammonia+Methane, maybe Water ice.

- Ocean: Methane.

- Atmo.: Nitrogen.

- Cond.: Cold.

4. "Pre-Archaean Earth"

- Solid: None.

- Ocean: None.

- Atmo.: Nitrogen.

- Cond.: Warm.

5. "Volcanic age Earth"

- Solid: None.

- Ocean: salty Water (also contains much carbonates and hydrocarbonates).

- Atmo.: Nitrogen + CarbonDioxide.

- Cond.: .

6. "Venus"

- Solid: None.

- Ocean: None.

- Atmo.: CarbonDioxide.

- Cond.: very hot, neverlasting greenhouse effect.

7. "Frozen Venus"

- Solid: CarbonDioxide ice layer.

- Ocean: None.

- Atmo.: CarbonDioxide.

- Cond.: Cold.

8. "Proterozoic Earth"

- Solid: None.

- Ocean: salty Water.

- Atmo.: Nitrogen+CarbonDioxide.

- Cond.: Warm.

9. "Present-day Earth"

- Solid: Soil (organic substrate mixed with mineral dust).

- Ocean: salty Water.

- Atmo.: Nitrogen + Oxygene.

- Cond.: Nice.

10. "Frozen Earth", "Europa", "Hanymede", "Callysto".

- Solid: Water ice.

- Ocean: Maybe salty water ocean under surface.

- Atmo.: leaky Oxygen, maybe also Nitrogen.

- Cond.: Cold.

- Remark: Either frozen Earth, or previously same as "Titan" but with great Water content.

11. "Carbon planet"

- Solid: organic compositions.

- Ocean: methanol.

- Atmo.: carbon oxides.

- Cond.: Warm.

- Remark: Hypothetical planet type in close proximity of white dwarf start. Very rich with carbon.

Edited December 25, 2014 by kerbiloid

[Camacha]

This thread reminds me of Jupiter, with its souposphere without real boundaries and a mysterious core with (probably) things like metallic hydrogen. The idea of something being pretty much endlessly deep is both exciting and frightening.

[lordmuffin]

What about a planet with liquid metal oceans? Or an atmosphere made of metallic crystals? What could be done with that planet? Could it be mined for materials?

[lajoswinkler]

Atmosphere of crystals isn't a daydream - Earth does have it. Just remember that everything is in equilibrium - ie. Water vapour exist with water droplets, water ice exist with snow or ice ground. Granted that carbon dioxide is more extreme so you need to get some views on the temp and the pressure first.

Earth does not have an atmosphere made of solids. It has a real, gaseous atmosphere where solids are transient phenomena, being poorly suspended by the gas and eventually growing so much they fall down.

For solid particles to be suspended, you need a fluid medium. It can be gas (atmosphere) or liquid (hydrosphere). Electric force can't be called an atmosphere. We don't have a name for it yet, IMHO.

of course the temperature range at which they are stable is exceedingly narrow, effectively precluding any kind of weather patterns...

14.06 ÃŽâ€t at 1 atmosphere, that sounds reasonably wide. There could be planets far from their stars that never became fully developed gas giants, with several bars of pressure, extremely cold, with nitrogen precipitation.

Edited December 25, 2014 by lajoswinkler

[Technical Ben]

Something between the ionosphere and magnetosphere? Ionsoupmagnetosphere?

Ah, nope, it's got a name (technically?) the Plasmasphere?

[kerbiloid]

Atmosphere can not be of crystals. Cloud of crystal is dust.

Gas giants have liquid metal oceans. They are totally covered with a metal hydrogen layer.

No more metal oceans are possible because planets are made of metal oxides and sulfides.

Alcaline metals are chemically active and always are bound in their salts. They just travel from one chemical entity to another.

Heavy metals which are more or less passive are being melt in depths, their density is much greater than the density of surrounding rock material. And once they have been melt, they just sink down to the planet core.

[lajoswinkler]

What about a planet with liquid metal oceans? Or an atmosphere made of metallic crystals? What could be done with that planet? Could it be mined for materials?

Rocks are vastly more abundant than metals, so it's not really expected to find such oceans. Molten lava, yes. Metals don't offer much elemental variety, either. Iron, nickel. Others are either in compounds or rare, dispersed, too heavy so they sink into cores...

Molten metals are much more volatile than stones. I don't see how such oceans could exist, they would sink into cores. Maybe transient, ephemeral puddles... maybe. Highly improbable.

Again, solids can not form atmospheres. Doesn't matter which solid. It's solid, so it falls on the ground.

Gas giants have liquid metal oceans. They are totally covered with a metal hydrogen layer.

That layer doesn't have a distinct phase border, so we can't really call it an ocean. Hydrogen just gets more stuffed and more conductive with depth. No sights to see down there. :/

Edited December 25, 2014 by lajoswinkler

[kerbiloid]

That layer doesn't have a distinct phase border, so we can't really call it an ocean. Hydrogen just gets more stuffed and more conductive with depth. No sights to see down there. :/

Then we have lost the last chance to met a liquid metal ocean. It's a pity.

[Armchair Rocket Scientist]

All right, more on all the chemicals that can form planetary oceans/atmospheres.

Hydrogen and helium are the primary component of gas giants and the outer envelopes of ice giants, but can also be retained by super-earths, especially at low temperatures. However, their boiling points are too low for them to exist as liquids on planetary surfaces: even hydrogen is a supercritical fluid about about 30 K.

Nitrogen, as I discussed previously, can form oceans, but they will be rare and mostly very shallow. However, because nitrogen is common, chemically inert, and relatively heavy, it will be a frequent component of the atmospheres of rocky or icy planets.

Oxygen is too chemically reactive to be stable in an atmosphere or ocean over geologic time. It will ONLY be present in significant quantities if it is being released by biological processes.

Carbon dioxide is likely to be a common component of the atmospheres of warmer oxygen-rich planets (above 200 Kelvins). It is fairly chemically stable and is the heaviest gas likely to be present in large quantities in atmospheres. Carbon dioxide can only exist in liquid form at very high pressures. The minimum is about 5 bars, but more than 20 is ideal. Nevertheless, it may still form oceans on moderately cool planets with thick atmospheres of other substances such as nitrogen and helium.

Water is extremely common, and in oxygen-rich systems is a major component of planets formed outside the frost line. However, water vapor in a planet's upper atmosphere can be split apart by UV light, at which point the hydrogen will escape to space. This process caused Venus to lose its original oceans. However, on cooler planets like Earth water freezes out lower in the atmosphere, preventing this. In addition, some planets will form with such large amounts of water that even over billions of years losses from photodissociation will be negligible. Current searches for extrasolar planets suggest that hot "ocean planets" with supercritical water oceans may be very common in the universe, such as Gliese 1214 b. Subsurface water oceans also seem to be very common on moons of cold gas giants.

Ammonia is rarer than water, and has a narrower liquid range. It is also even more susceptible to photodissociation. However, large amounts of ammonia may form on cold planets with excess hydrogen and nitrogen. Ammonia-rich atmospheres will probably be lost to photodissociation, but ammonia oceans may remain stable over geologic time, especially on planets orbiting K or M stars, which produce less UV light than the sun. In addition, some subsurface oceans on icy moons may actually be a mixture of water and ammonia, which remains liquid at temperatures where pure water would freeze.

Methane has a narrow liquid range of about 20 Kelvins, but it is confirmed to form Titan's lakes and seas. Methane also has the interesting property that when exposed to stellar radiation it forms more complex hydrocarbons. While it is vulnerable to photodissociation, on "carbon planets" it may be so abundant that these losses are negligible. Depending on the environment, it may form lakes, oceans, or atmospheres at a variety of temperatures.

For extremely hot planets, rock and metal may form oceans and atmospheres. Silicate rocks such as granite and basalt start to melt at around 1000 K, and rocky planets have been found with estimated peak surface temperatures double that. Such planets will be tidally locked to their stars, except in the rare and short-lived case of rocky planets orbiting slightly above the surfaces of post-main-sequence stars, and will have magma oceans on the light side. These planets may also have atmospheres of rock vapor.

[kerbiloid]

Nitrogen, as I discussed previously, can form oceans, but they will be rare and mostly very shallow.

As nitrogen appears from ammonia, much more probable are stable ammonia ocean (if it's cold) or stable nitrogen atmosphere (if it's warm).

Nitrogen ocean would be a virtual thing.

Oxygen is too chemically reactive to be stable in an atmosphere or ocean over geologic time.

It will ONLY be present in significant quantities if it is being released by biological processes.

Nevertheless, it already presents in Earth atmosphere for 0.5 billion years, which looks enough a geological time.

At least, continents changed their positions several times while this is so.

For extremely hot planets, rock and metal may form oceans and atmospheres.

Silicate rocks such as granite and basalt start to melt at around 1000 K

Of course, rocks and metals can be melt if temperature is high.

But alcaline metals would not be pure - they will be absorbed by lava.

Si and Al just will stay a silicate lava - not molten metal.

And iron and other heavy metals are 3 times more dense than granite or basalt lava and will sink down until they arrive to a so high-pressure depth, when again become solid.

[Armchair Rocket Scientist]

As nitrogen appears from ammonia, much more probable are stable ammonia ocean (if it's cold) or stable nitrogen atmosphere (if it's warm).

Nitrogen ocean would be a virtual thing.

Whoops, I forgot about the nitrogen and hydrogen thing. A simplified gibbs free energy calculation at constant temperature indicates that below about 400 Kelvin nitrogen and hydrogen will spontaneously combine to form ammonia. Even at Earth's temperature atmospheric nitrogen would spontaneously form ammonia if sufficient hydrogen was present.

Fortunately, there is not sufficient hydrogen. On both Earth and Titan the available hydrogen is locked up as water, and in Titan's case methane.

This means that a nitrogen ocean will NOT be stable in the presence of a hydrogen atmosphere: the two substances will react to form ammonia, which freezes. Ammonia ice and liquid nitrogen are similar in density, so I'm not sure if it would sink to the bottom or form a floating crust.

However, if a planet or moon cannot retain hydrogen or otherwise is hydrogen-poor, nitrogen oceans are still possible, with either a nitrogen or helium atmosphere.

Nevertheless, [oxygen] already presents in Earth atmosphere for 0.5 billion years, which looks enough a geological time.

At least, continents changed their positions several times while this is so.

Yes, that's because Earth has a huge amount of photosynthetic organisms which are constantly releasing oxygen. If all life on Earth suddenly died, the oxygen wouldn't last very long. IIRC it would last a few thousand years of photosynthesis stopped, but that's with organisms consuming it. Nevertheless, it probably wouldn't last more than a few million years or so on its own. For example, basalt rock eventually oxidizes to form minerals like hematite.

[lajoswinkler]

Hydrogen and nitrogen reaction at standard conditions is incredibly slow, so slow you can ignore it even over aeons.