Atmospheres and Worldbuilding... What I Learned

[Bamax]

Our atmosphere is mostly nitrogen mixed with enough oxygen to breath. Nitrogen is mostly non-reactive, but not totally.

It turns out that there are no known other substitutes for nitrogen in an oxygenated atmosphere that could support the vast variety of lifeforms we know on Earth.

The obvious gases similar to nitrogen are noble gases, and of them the arguably safest is argon.

So make a oxygen/argon atmosphere? Not so fast. Argon does not react with ANYTHING unless you brute force it, and even that does not remain stable for long scientists learned. And the element used to make this work was fluorine, which is not exactly an element I think living things use much if at all.

Besides, nitrogen is important for plants which use it and creatures that deposit it into the soil for plants to use later.

Does argon interact with plants? Experiments thus far show bean plants absorb argon gas but nothing more.

Argon chemical compounds either do not exist, or only when forced to under controlled conditions.


My conclusion: Earth life is optimized for life. It is better to build upon a model that actually works than throw it out trying stuff that does not EXIST because it is non-optimal for life to begin with.

Even so, life can still be heavily modified. There is nothing in physics that prevents a creature that looks like any of Arioch's races from actually living.

The only thing that is an obvious impossibilty are the Loroi superpowers that go outside the bounds of known physics.

Part of the reason oxygenated life works is that oxygen reactions are so powerful.

If one designed life that breathed somthing OTHER than oxygen, they would probably be less energetic life forms as well.

Rocket engines use oxidizer for that very reason. Powerful chemical reaction. Plenty of energy.

[Arioch]

Helium, Neon, Argon, etc. are called "noble gases" specifically because they don't react chemically with anything. They have full electron shells, and so have no potential to either give up or or receive electrons, which is what makes chemical reactions happen. So noble gases in an atmosphere would be inert and probably irrelevant to whatever life was trying to evolve on a planet. But I think they're not common enough to be the major component of a planetary atmosphere; Helium is common, but on an Earth-sized planet it's constantly being lost to space.

The atmospheres of Venus and Mars are mainly carbon dioxide. I'm not sure why Earth has such a comparatively high concentration of nitrogen, since it presumably formed from the same material in the inner protoplanetary disc as the other inner planets. Oxygen is highly reactive, so the only way (that I know of) to have oxygen in an atmosphere is if biological processes are creating it. In Earth's case, photosynthetic life consumes carbon dioxide and produces oxygen. Early life didn't require oxygen because there wasn't any; organisms adapted to use it, because you can get very energetic reactions out of it.

Rather than thinking about it as "Earth's conditions are optimized for life," I think the way to look at it is, "life on Earth is optimized for Earth's conditions." I think it's possible for very different biochemical systems to evolve in very different planetary conditions. It's probable that life on Earth first arose in the deep ocean, feeding off hydrogen sulfide from hydrothermal vents in volcanic fissures; it didn't require oxygen and the composition of the atmosphere was almost entirely irrelevant. It's possible that some alien organisms don't need to "breathe" at all.

[Bamax]

Helium, Neon, Argon, etc. are called "noble gases" specifically because they don't react chemically with anything. They have full electron shells, and so have no potential to either give up or or receive electrons, which is what makes chemical reactions happen. So noble gases in an atmosphere would be inert and probably irrelevant to whatever life was trying to evolve on a planet. But I think they're not common enough to be the major component of a planetary atmosphere; Helium is common, but on an Earth-sized planet it's constantly being lost to space.

The atmospheres of Venus and Mars are mainly carbon dioxide. I'm not sure why Earth has such a comparatively high concentration of nitrogen, since it presumably formed from the same material in the inner protoplanetary disc as the other inner planets. Oxygen is highly reactive, so the only way (that I know of) to have oxygen in an atmosphere is if biological processes are creating it. In Earth's case, photosynthetic life consumes carbon dioxide and produces oxygen. Early life didn't require oxygen because there wasn't any; organisms adapted to use it, because you can get very energetic reactions out of it.

Rather than thinking about it as "Earth's conditions are optimized for life," I think the way to look at it is, "life on Earth is optimized for Earth's conditions." I think it's possible for very different biochemical systems to evolve in very different planetary conditions. It's probable that life on Earth first arose in the deep ocean, feeding off hydrogen sulfide from hydrothermal vents in volcanic fissures; it didn't require oxygen and the composition of the atmosphere was almost entirely irrelevant. It's possible that some alien organisms don't need to "breathe" at all.

As planets go, Earth is rather unique, and not only because of the teeming life it has upon it.

Liquid water on the surface... that's rather not common in our solar system.

A helpful moon, without which would have disastrous consequences for life.

An axial tllt inclination that also helps, since we would have disasters otherwise.

And being in the goldilocks zone, and also in a place where Jupiter diverts a lot of asteroids away from it.

https://www.space.com/5595-earth-specia ... anets.html

[Arioch]

Every star will have a goldilocks zone, so I don't think there's anything unique about Earth in that regard.

Liquid water is not unique to Earth even in this solar system; numerous moons of the gas giants have subsurface oceans and volcanic activity that could feed hydrothermal vents and life.

I think the Moon plays a key role in providing tidal stresses that help keep Earth's interior molten to provide the dynamo that generates the magnetic field that protects our atmosphere. But moons are not rare; more bodies in our solar system have them than not.

I think Jupiter's role in deflecting asteroids in overstated... Jupiter's presence is probably the reason that there's an asteroid field between it and Mars instead of another planet, increasing the number of asteroids in play. I'm not an astrophysicist, but it seems to me that random deflections are as much a hazard as a help. However, gas giants in the outer parts of solar systems are probably not rare. Also, asteroids can cause mass extinctions, but it takes an unusually big one to exterminate all life on a planet.

An axial tllt inclination that also helps, since we would have disasters otherwise.

Axial tilts are also not rare, but in what way does an axial tilt prevent disasters?

[Cthulhu]

Our planet is indeed somewhat special regarding a combination of factors that allow complex life:
1. Size and mass, since a certain force of gravity is needed to retain an atmosphere
2. An active magnetic field, because otherwise, the atmosphere would lose the lighter gases like oxygen or nitrogen but also water, too
3. Being in the green zone around our sun

None of the other planets have similarly good factors, even if we tried to improve them trough terraforming, for instance. No currently envisonable technology can fix Mars' low gravity, for example.

[Bamax]

Every star will have a goldilocks zone, so I don't think there's anything unique about Earth in that regard.

Liquid water is not unique to Earth even in this solar system; numerous moons of the gas giants have subsurface oceans and volcanic activity that could feed hydrothermal vents and life.

I think the Moon plays a key role in providing tidal stresses that help keep Earth's interior molten to provide the dynamo that generates the magnetic field that protects our atmosphere. But moons are not rare; more bodies in our solar system have them than not.

I think Jupiter's role in deflecting asteroids in overstated... Jupiter's presence is probably the reason that there's an asteroid field between it and Mars instead of another planet, increasing the number of asteroids in play. I'm not an astrophysicist, but it seems to me that random deflections are as much a hazard as a help. However, gas giants in the outer parts of solar systems are probably not rare. Also, asteroids can cause mass extinctions, but it takes an unusually big one to exterminate all life on a planet.

An axial tllt inclination that also helps, since we would have disasters otherwise.

Axial tilts are also not rare, but in what way does an axial tilt prevent disasters?

Virtually all I know (and would rather not know) I learned from google.

In this case all I typed in the search bar was:

earths axial tilt helps life


Type it in and a whole host of reasons will show up.. more than I can list here.

But in short they are: The seasons are a byproduct of the tilt. Take them away and... suffer. Also elsewhere it is said it helps with oxygen production.

To quote the article:
This tilt is why we have seasons - the tilt away from or towards the Sun influences seasonal variability. Seasonal temperature changes also influence the oceans, resulting in convective mixing and currents, and the availability of nutrients.

As for water oceans, water on the surface itself is unique yes, subsurface ocean is more common.

And I have not a clue what surface oceans Jupiter, Saturn, and Neptune have.... but it's not likely water.

[Bamax]

Our planet is indeed somewhat special regarding a combination of factors that allow complex life:
1. Size and mass, since a certain force of gravity is needed to retain an atmosphere
2. An active magnetic field, because otherwise, the atmosphere would lose the lighter gases like oxygen or nitrogen but also water, too
3. Being in the green zone around our sun

None of the other planets have similarly good factors, even if we tried to improve them trough terraforming, for instance. No currently envisonable technology can fix Mars' low gravity, for example.

If you are biologically immortal you could engineer a way to crash several moons into mars to increase it's mass.

Unless one has really uber laser platforms capable of uber pulse shots, this would likely take several millenia to pull off.

Theoretically possible... just time consuming.

[gaerzi]

In fact the first mass extinction we know of is when the Earth's atmosphere started getting flooded by the oxygen pooped by all these cyanobacteriae.

See, oxygen is a very strong oxidizer. In fact, it's even the origin of its name: oxidation generator. (Hydrogen is water generator, and nitrogen is baking soda generator. True! Look it up.) And oxidation in an organism is something very undesired and toxic. That's why antioxidants are such a big buzzword in health food fads.

Anyway at some point, some sort of organism managed to not just survive oxygen but even find a way to use its horrifying properties to its own benefit. That was kind of like domesticating fire, when you think about it. So these organisms were all, "look at me, I can harness oxygen for energy, lol, I'm the best!" and that was when another organism said, "oh yeah? well, I can harness you to harness oxygen for me, then!" and this is the story of why you have mitochondria in your cells.

[Cthulhu]

If you are biologically immortal you could engineer a way to crash several moons into mars to increase it's mass.

Unless one has really uber laser platforms capable of uber pulse shots, this would likely take several millenia to pull off.

Theoretically possible... just time consuming.

Since Mars is very light (0,38 of Earth's gravity and 10,7% of its mass), it will require a lot of planetary material. In fact, the entire asteroid belt, all the moons combined, and even Mercury added for good measure, too, won't be enough. Regardless, all this bombardment will turn Mars into a ball of lava, and it will take eons to cool down. Moving all that and then waiting for the outcome is simply impossible.

Relative masses of solid Solar system bodies:

[Bamax]

Was not aware of that. Thanks. So if I don't like losing and still want 1g mars.


Make hollow subterranean areas of mars with uber surface lasers. Reinforce the ceilings of these artficial caves as much as necessary.

Next use uber space lasers to cause mars to spin via molten and plasma ejecta plumes.

Once mars is spinning enough for 1g in the cave ceilings via centripetal rotation force, then you have gravity.

Main issue now is landing on mars plus wind storms may result.

Just turned mars into a giant rotating station that kind of looks like Apokalips



]

[Cthulhu]

Was not aware of that. Thanks. So if I don't like losing and still want 1g mars.


Make hollow subterranean areas of mars with uber surface lasers. Reinforce the ceilings of these artficial caves as much as necessary.

Next use uber space lasers to cause mars to spin via molten and plasma ejecta plumes.

Once mars is spinning enough for 1g in the cave ceilings via centripetal rotation force, then you have gravity.

Main issue now is landing on mars plus wind storms may result.

Just turned mars into a giant rotating station that kind of looks like Apokalips

That will be an absurd waste of energy. Instead, you'd be better off using all that interplanetary debris to create a rotating habitat. As I said, currently there's no way to have our familiar 1g on Mars. Whether this will turn into a problem is still unknown, because there are (obviously) no studies about how low gravity affects humans in the long term. Educated guesses may hint at the possibility that martian-born and raised humans may not be able to live on Earth, at least without extensive therapy.

[Bamax]

Was not aware of that. Thanks. So if I don't like losing and still want 1g mars.


Make hollow subterranean areas of mars with uber surface lasers. Reinforce the ceilings of these artficial caves as much as necessary.

Next use uber space lasers to cause mars to spin via molten and plasma ejecta plumes.

Once mars is spinning enough for 1g in the cave ceilings via centripetal rotation force, then you have gravity.

Main issue now is landing on mars plus wind storms may result.

Just turned mars into a giant rotating station that kind of looks like Apokalips

That will be an absurd waste of energy. Instead, you'd be better off using all that interplanetary debris to create a rotating habitat. As I said, currently there's no way to have our familiar 1g on Mars. Whether this will turn into a problem is still unknown, because there are (obviously) no studies about how low gravity affects humans in the long term. Educated guesses may hint at the possibility that martian-born and raised humans may not be able to live on Earth, at least without extensive therapy.

Blasting mars to bits may cause other problems. All planets affect each other via gravity. Kill mars and you may invite a collision with Earth later with another world... or at least with some of the martian debris we blasted.

Still... in theory it could work, and the same uber lasers could push away incoming debris or planets as well.


Low g is no good. As you said, body would be really weak on Earth, but I reckon it could adapt over time to Eatth, since humans are designed for Earth anyway.

[Arioch]

Seasons make life easier in the northern and southern latitudes of a planet, but life near the equator of a planet will be pretty much the same whether there are seasons or not. I don't see what that has to do with preventing disaster.

But even if we accept that it's necessary for a planet to have seasons for life to flourish, axial tilt is the norm, not the exception. Axial tilts of the major bodies in our solar system (in degrees as of 2010) are:

Sun: 7.25
Mercury: 0.01
Venus: 2.64
Earth: 23.44
Moon: 1.54
Mars: 25.19
Jupiter: 3.12
Saturn: 10.66
Uranus: 82.23
Neptune: 28.33
Pluto: 57.47

Our planet is indeed somewhat special regarding a combination of factors that allow complex life:
1. Size and mass, since a certain force of gravity is needed to retain an atmosphere
2. An active magnetic field, because otherwise, the atmosphere would lose the lighter gases like oxygen or nitrogen but also water, too
3. Being in the green zone around our sun

None of the other planets have similarly good factors, even if we tried to improve them trough terraforming, for instance. No currently envisonable technology can fix Mars' low gravity, for example.

Earth's parameters are unique in our solar system, but they won't be unique in other star systems, which is what I thought we were talking about.

[Bamax]

Seasons make life easier in the northern and southern latitudes of a planet, but life near the equator of a planet will be pretty much the same whether there are seasons or not. I don't see what that has to do with preventing disaster.

But even if we accept that it's necessary for a planet to have seasons for life to flourish, axial tilt is the norm, not the exception. Axial tilts of the major bodies in our solar system (in degrees as of 2010) are:

Sun: 7.25
Mercury: 0.01
Venus: 2.64
Earth: 23.44
Moon: 1.54
Mars: 25.19
Jupiter: 3.12
Saturn: 10.66
Uranus: 82.23
Neptune: 28.33
Pluto: 57.47

Our planet is indeed somewhat special regarding a combination of factors that allow complex life:
1. Size and mass, since a certain force of gravity is needed to retain an atmosphere
2. An active magnetic field, because otherwise, the atmosphere would lose the lighter gases like oxygen or nitrogen but also water, too
3. Being in the green zone around our sun

None of the other planets have similarly good factors, even if we tried to improve them trough terraforming, for instance. No currently envisonable technology can fix Mars' low gravity, for example.

Earth's parameters are unique in our solar system, but they won't be unique in other star systems, which is what I thought we were talking about.

There is precision tilting involved too:



But there's a limit. Uranus, for example, is tilted at 98 degrees from the perpendicular. Such an extreme tilt would result in seasonality that may be too extreme for life. A small tilt, also, might not produce enough seasonality to encourage the right level of nutrient availability. This suggests there may be a Goldilocks zone for axial tilt, too - neither too extreme, nor too small.

It's another parameter we can use to help narrow down planets elsewhere in the galaxy that are likely to harbor life as we know it.


From this article:

https://www.sciencealert.com/an-axial-t ... e-universe

[Arioch]

But there's a limit. Uranus, for example, is tilted at 98 degrees from the perpendicular. Such an extreme tilt would result in seasonality that may be too extreme for life. A small tilt, also, might not produce enough seasonality to encourage the right level of nutrient availability. This suggests there may be a Goldilocks zone for axial tilt, too - neither too extreme, nor too small.

The seasons would be more extreme, but the year would still be the same length. This is a problem on Uranus which has a year that's 84 Earth years long, but on a terrestrial world it would be roughly like the Earth year (or much shorter for a dimmer star). On Earth there is life even within the arctic and antarctic circles, which get zero sunlight through winter. Larger animals migrate, but smaller ones either hibernate or just adapt to the cold. And again, since it seems that life starts in the deep water, it doesn't necessarily matter what the surface temperature is.

Also, planets with wildly different rotations will have very different weather patterns to Earth, so taking Earth and extrapolating has limited usefulness. It was previously thought that planets tidelocked to their sun (and so have one face that is permanently dark) would be uninhabitable, as the light side would bake and the dark side would get so cold that any water or atmosphere would freeze solid. However, more recent simulations suggest that if the planet started out with an atmosphere and surface water (tidelocked planets don't start that way; it happens over time), the water vapor would form dense clouds at the center of the hemisphere facing the sun, mitigating the intensity of the sunlight there, and the temperature differential would cause jetstreams and ocean currents that would continuously transfer heat to the dark side of the planet, potentially keeping it above the freezing temperature of the atmosphere. There could be a broad habitable band near the terminator between day and night.

TLDR: the more we learn about planetary systems, the more complex and interesting they turn out to be. There will be a lot of Earthlike planets in the galaxy, but a planet doesn't need to be anything like Earth to support life.

[icekatze]

hi hi

If we wait a billion years or two, there's like a 2% chance that Mercury will gradually be kicked out of its orbit by the pull from Jupiter. If it crashes into Mars, it won't get up to 1g, but it might create a magnetic field to block solar winds. Or if it crashes into Venus and knocks it into a wider orbit, it might turn into a terraforming candidate. (For whatever amount of time is left before the sun turns into a red giant at that point.)

Mars has enough gravity to prevent Oxygen and Nitrogen from escaping due to thermal causes (Jeans escape, etc.), so if it had a magnetic field, it could potentially sustain a breathable atmosphere.

Regardless, any off Earth colonies are probably going to need to be subterranean for the foreseeable future.

For simple single cell organisms though, Europa and Enceladus could potentially support life as we know it.