ConwayLife.com

I just finished watching the existing episodes of Biblaridion's series on speculative evolution on an alien planet, and I kind of wanted to do it myself, so here's the thread dedicated to it. I would like the planet to be a terrestrial super-Earth, though super-Earth means any planet whose mass is in between 1-10 Earth masses, so I'm leaving it up to others to determine exactly how heavy this planet will be. Please don't forget that gravity does not scale up linearly with planetary mass. This planet will also have no abiotic oxygen, all oxygen will come from cyanobacteria analogues.

We probably want atmospheric oxygen eventually in order for land-based lifeforms to have protection from ultraviolet light. I'd like the atmosphere to have some methane or ethane, but I'm concerning about that, combined with the oxygen, making it vulnerable to combusting.

MathAndCode wrote: ↑

January 5th, 2021, 12:57 pm

We probably want atmospheric oxygen eventually in order for land-based lifeforms to have protection from ultraviolet light. I'd like the atmosphere to have some methane or ethane, but I'm concerning about that, combined with the oxygen, making it vulnerable to combusting.

I was already thinking of having methane in the atmosphere. This planet can hold a denser atmosphere as well because of its higher gravity.

Wikipedia wrote: ↑

January 5th, 2021, 12:57 pm

At room temperature, ethane is an extremely flammable gas. When mixed with air at 3.0%–12.5% by volume, it forms an explosive mixture.

Schiaparelliorbust wrote: ↑

January 5th, 2021, 1:08 pm

I was already thinking of having methane in the atmosphere. This planet can hold a denser atmosphere as well because of its higher gravity.

Wikipedia wrote: ↑

January 5th, 2021, 12:57 pm

At room temperature, ethane is an extremely flammable gas. When mixed with air at 3.0%–12.5% by volume, it forms an explosive mixture.

the Wikipedia page about methane wrote:As a gas it is flammable over a range of concentrations (5.4–17%) in air at standard pressure.

I guess that we can't put a lot of hydrocarbons in the air, then. The explosive limit might be a little higher if the atmosphere doesn't have as much oxygen, but I would expect that the denser atmosphere would at least cancel that out. I want to do something different, though. What if we increase the atmospheric concentration of ammonia? Then maybe plants could find a way to get nitrogen directly from the air instead of having to rely on bacteria.

MathAndCode wrote: ↑

January 5th, 2021, 1:15 pm

the Wikipedia page about methane wrote:As a gas it is flammable over a range of concentrations (5.4–17%) in air at standard pressure.

I guess that we can't put a lot of hydrocarbons in the air, then. The explosive limit might be a little higher if the atmosphere doesn't have as much oxygen, but I would expect that the denser atmosphere would at least cancel that out. I want to do something different, though. What if we increase the atmospheric concentration of ammonia? Then maybe plants could find a way to get nitrogen directly from the air instead of having to rely on bacteria.

5-10% methane is also explosive. Ammonia is also basic and corrosive, but I bet that the creatures on this planet can find a way around that. Let's keep the concentration low like <5%. Let's still have some methane though.

Schiaparelliorbust wrote: ↑

January 5th, 2021, 1:28 pm

Ammonia is also basic and corrosive, but I bet that the creatures on this planet can find a way around that.

Yes, since they could become used to the alkalinity, and could simply develop external layers for which ammonia is not corrosive.

Schiaparelliorbust wrote: ↑

January 5th, 2021, 1:28 pm

Let's still have some methane though.

How about 1.2% methane and 0.4% ethane?

MathAndCode wrote: ↑

January 5th, 2021, 1:49 pm

Yes, since they could become used to the alkalinity, and could simply develop external layers for which ammonia is not corrosive.

Schiaparelliorbust wrote: ↑

January 5th, 2021, 1:28 pm

Let's still have some methane though.

How about 1.2% methane and 0.4% ethane?

Actually I don't think there should be much methane unless there's some biological process that can get rid of it. Pre-industrial age methane concentrations are around 670-690 ppb and is a very potent greenhouse gas. It is 84 times more potent than CO2. We could also have high CO2 concentrations as well at first. Oxygen would probably be lethal at first anyway. It would oxidise organic molecules before they could form life probably.

Schiaparelliorbust wrote: ↑

January 5th, 2021, 1:58 pm

Actually I don't think there should be much methane unless there's some biological process that can get rid of it. Pre-industrial age methane concentrations are around 670-690 ppb and is a very potent greenhouse gas. It is 84 times more potent than CO2. We could also have high CO2 concentrations as well at first. Oxygen would probably be lethal at first anyway. It would oxidise organic molecules before they could form life probably.

We could put the planet farther from its sun in order to compensate, but life probably would develop some process that consumes it, so it's probably best to not have a lot to begin with.

Schiaparelliorbust wrote: ↑

January 5th, 2021, 1:58 pm

Oxygen would probably be lethal at first anyway. It would oxidise organic molecules before they could form life probably.

Yes, but the organisms are going to need to get energy through redox reactions, so they will need to have access to some oxidant. Carbon dioxide has carbon in the +4 oxidation state, but its three-center four-electron bonds make it too stable for reactions that consume it to provide much energy. Isocyanic acid can act as an oxidizing agent, and it has a positive enthalpy of formation, but the latter fact means that it will not form naturally in large quantities. (Otherwise, it could form from ammonia reacting with carbon dioxide.) Another possibility is for organisms to store oxidizing agents and collect reducing agents from the environment as needed. This would be the opposite of what animals and plants do on Earth, but there is no reason why it couldn't work. Possible options for this include isocyanic acid, nitrogen oxides/oxyanions, and sulfur oxides/oxyanions.

MathAndCode wrote: ↑

January 5th, 2021, 2:26 pm

We could put the planet farther from its sun in order to compensate, but life probably would develop some process that consumes it, so it's probably best to not have a lot to begin with.

Yes, let's not put it too far. "Bacteria" can survive much higher temperatures, so keeping the planet cool a the start won't be a big priority.

MathAndCode wrote: ↑

January 5th, 2021, 2:26 pm

Yes, but the organisms are going to need to get energy through redox reactions, so they will need to have access to some oxidant. Carbon dioxide has carbon in the +4 oxidation state, but its three-center four-electron bonds make it too stable for reactions that consume it to provide much energy. Isocyanic acid can act as an oxidizing agent, and it has a positive enthalpy of formation, but the latter fact means that it will not form naturally in large quantities. (Otherwise, it could form from ammonia reacting with carbon dioxide.) Another possibility is for organisms to store oxidizing agents and collect reducing agents from the environment as needed. This would be the opposite of what animals and plants do on Earth, but there is no reason why it couldn't work. Possible options for this include isocyanic acid, nitrogen oxides/oxyanions, and sulfur oxides/oxyanions.

Before oxygen, bacteria used sulfur as an oxidant. There was even something something called the Great Oxidation Event, which killed most bacteria. Of those that died, sulfur-reducing bacteria now only live at places with low oxygen levels like the ocean depths. Maybe they could be like that? Also, if these creatures can find a way to store oxygen, they would have to find some way of preventing it from diffusing or controlling when it can diffuse. I don't really see it happening at bacterial scales because diffusion happens, AFAIR, at sizes smaller than 1mm.

MathAndCode wrote: ↑

January 5th, 2021, 1:49 pm

Schiaparelliorbust wrote: ↑

January 5th, 2021, 1:28 pm

Ammonia is also basic and corrosive, but I bet that the creatures on this planet can find a way around that.

Yes, since they could become used to the alkalinity, and could simply develop external layers for which ammonia is not corrosive.

Schiaparelliorbust wrote: ↑

January 5th, 2021, 1:28 pm

Let's still have some methane though.

How about 1.2% methane and 0.4% ethane?

Actually, there are many chemosynthetic organisms on the bottom of the ocean floor (on this planet) that require many forms or hydrocarbons for cellular respiration. It could be entirely plausible that organisms could exist in an atmosphere of hydrocarbons and be able to breath it.

HelicopterCat3 wrote: ↑

January 6th, 2021, 10:03 am

Actually, there are many chemosynthetic organisms on the bottom of the ocean floor (on this planet) that require many forms or hydrocarbons for cellular respiration. It could be entirely plausible that organisms could exist in an atmosphere of hydrocarbons and be able to breath it.

Yes, but that's deep in the ocean. In the atmosphere, it becomes explosive. Even a single spark would be disastrous.

Schiaparelliorbust wrote: ↑

January 6th, 2021, 10:07 am

HelicopterCat3 wrote: ↑

January 6th, 2021, 10:03 am

Actually, there are many chemosynthetic organisms on the bottom of the ocean floor (on this planet) that require many forms or hydrocarbons for cellular respiration. It could be entirely plausible that organisms could exist in an atmosphere of hydrocarbons and be able to breath it.

Yes, but that's deep in the ocean. In the atmosphere, it becomes explosive. Even a single spark would be disastrous.

Oh yeah. Oxygen. Pressure. Fundamental gas physics. Forgot about those...
I suppose I have another question, would organisms be able to develop in other liquid environments other than water is they have the correct materials solutes in them (since water is the universal solvent it makes it easy for life to develop in it but I'm asking if other liquids could work in a similar, but with less evolutionary possibilities)

HelicopterCat3 wrote: ↑

January 6th, 2021, 10:12 am

Oh yeah. Oxygen. Pressure. Fundamental gas physics. Forgot about those...
I suppose I have another question, would organisms be able to develop in other liquid environments other than water is they have the correct materials solutes in them (since water is the universal solvent it makes it easy for life to develop in it but I'm asking if other liquids could work in a similar, but with less evolutionary possibilities)

I will come back later in about an hour. I have to go now. I will edit this post with my reply.
Edit: There are two problems with this:
1)I don't know of any substances that are liquid at room temperature that can occur abiotically in very large amounts. If there are any, please tell me.
2) We don't really know how life can function in non-water liquids. In Biblaridion's series, he said that you shouldn't break the rules without knowing them, and we don't really know the rules of creatures that could live in an environment like this.

HelicopterCat3 wrote: ↑

January 6th, 2021, 10:12 am

Oh yeah. Oxygen. Pressure. Fundamental gas physics. Forgot about those...
I suppose I have another question, would organisms be able to develop in other liquid environments other than water is they have the correct materials solutes in them (since water is the universal solvent it makes it easy for life to develop in it but I'm asking if other liquids could work in a similar, but with less evolutionary possibilities)

Since ammonia and carbon dioxide in the atmosphere have already been pitched, formamide could be an interesting solvent.

Kazyan wrote: ↑

January 6th, 2021, 10:36 am

HelicopterCat3 wrote: ↑

January 6th, 2021, 10:12 am

Oh yeah. Oxygen. Pressure. Fundamental gas physics. Forgot about those...
I suppose I have another question, would organisms be able to develop in other liquid environments other than water is they have the correct materials solutes in them (since water is the universal solvent it makes it easy for life to develop in it but I'm asking if other liquids could work in a similar, but with less evolutionary possibilities)

Since ammonia and carbon dioxide in the atmosphere have already been pitched, formamide could be an interesting solvent.

An atmosphere of CO2 and NH4 and oceans of formamide? Sounds neat.

HelicopterCat3 wrote: ↑

January 6th, 2021, 11:17 am

An atmosphere of CO2 and NH4 and oceans of formamide? Sounds neat.

I edited my above post.
How would that much formamide even be there in the first place? Also, we don't know anything about life in something like formamide, as I said in my edit.

Here is a preliminary atmosphere based on what users have asked for directly (e.g. ammonia) or implied (e.g. water vapor because the planet has oceans). Feel free to suggest tweaks/changes.
50% dinitrogen
15% carbon dioxide
15% ammonia
6% sulfur oxides
5% carbon monoxide (in order for formamide to form)
2% dioxygen
1.5% methane
1% water vapor
1% hydrogen sulfide
0.6% ethane
0.4% isocyanic acid
2.5% other

MathAndCode wrote: ↑

January 6th, 2021, 12:13 pm

Here is a preliminary atmosphere based on what users have asked for directly (e.g. ammonia) or implied (e.g. water vapor because the planet has oceans). Feel free to suggest tweaks/changes.
50% dinitrogen
15% carbon dioxide
15% ammonia
5% sulfur oxides
5% carbon monoxide (in order for formamide to form)
2% dioxygen
2% hydrogen sulfide
1.5% methane
1% water vapor
0.6% ethane
0.4% isocyanic acid
2.5% other

I think there should be no oxygen at all at first. In your atmosphere, since there's carbon monoxide it would bond with it anyway creating CO2. What would formamide do when in water? Also, how heavy will this planet be?

Schiaparelliorbust wrote: ↑

January 6th, 2021, 12:21 pm

I think there should be no oxygen at all at first.

Yes, I had thought of the fact that dioxygen is typically formed by living organisms and that this atmosphere is supposed to be before life and had been meaning to clarify it with you.

Schiaparelliorbust wrote: ↑

January 6th, 2021, 12:21 pm

What would formamide do when in water?

Formamide and water are miscible, i.e. they can dissolve each other in any proportion.

Schiaparelliorbust wrote: ↑

January 6th, 2021, 12:21 pm

Also, how heavy will this planet be?

Maybe it should have 20% more surface gravity than Earth?

MathAndCode wrote: ↑

January 6th, 2021, 12:40 pm

Schiaparelliorbust wrote: ↑

January 6th, 2021, 12:21 pm

I think there should be no oxygen at all at first.

Yes, I had thought of the fact that dioxygen is typically formed by living organisms and that this atmosphere is supposed to be before life and had been meaning to clarify it with you.

Schiaparelliorbust wrote: ↑

January 6th, 2021, 12:21 pm

What would formamide do when in water?

Formamide and water are miscible, i.e. they can dissolve each other in any proportion.

Schiaparelliorbust wrote: ↑

January 6th, 2021, 12:21 pm

Also, how heavy will this planet be?

Maybe it should have 20% more surface gravity than Earth?

Perhaps a ratio of formamide to water could allow for interesting aquatic life. 20% more surface gravity would probably mean that the creatures would evolve with a much different (probably stronger and more supportive) bone structure than beings on Earth.

MathAndCode wrote: ↑

January 6th, 2021, 12:40 pm

Formamide and water are miscible, i.e. they can dissolve each other in any proportion.

I know that, I should have specified. Is there anything else they do together?

MathAndCode wrote: ↑

January 6th, 2021, 12:40 pm

Maybe it should have 20% more surface gravity than Earth?

Ok, that sounds good.

HelicopterCat3 wrote: ↑

January 6th, 2021, 12:45 pm

Perhaps a ratio of formamide to water could allow for interesting aquatic life. 20% more surface gravity would probably mean that the creatures would evolve with a much different (probably stronger and more supportive) bone structure than beings on Earth.

Yes, they would have more muscle and bone mass and would be smaller than Earth creatures.

Schiaparelliorbust wrote: ↑

January 6th, 2021, 1:00 pm

I know that, I should have specified. Is there anything else they do together?

They could react to form ammonia and formic acid. Also, if certain oxides are present, which could happen as minerals in rocks on the seafloor, then they can cause formamide to split into water and hydrogen cyanide.

MathAndCode wrote: ↑

January 6th, 2021, 1:41 pm

They could react to form ammonia and formic acid. Also, if certain oxides are present, which could happen as minerals in rocks on the seafloor, then they can cause formamide to split into water and hydrogen cyanide.

Umm hydrogen cyanide? Is there any way to get around this? Because I don't think even the creatures on this planet will tolerate it. Formic acid might be okay at low concentrations. It's a strong acid (pH 2.3).

Schiaparelliorbust wrote: ↑

January 6th, 2021, 2:16 pm

Umm hydrogen cyanide? Is there any way to get around this? Because I don't think even the creatures on this planet will tolerate it. Formic acid might be okay at low concentrations. It's a strong acid (pH 2.3).

They can simply evolve to tolerate it and even use it to their advantage. It can be useful as a building block for other biomolecules, and it can serve as an electron acceptor/oxidizing agent in certain contexts, which could be used to help drive exergonic reactions to power biological processes.

MathAndCode wrote: ↑

January 6th, 2021, 2:32 pm

They can simply evolve to tolerate it and even use it to their advantage. It can be useful as a building block for other biomolecules, and it can serve as an electron acceptor/oxidizing agent in certain contexts, which could be used to help drive exergonic reactions to power biological processes.

The toxicity of cyanide is linked mainly to the cessation of aerobic cell metabolism. Cyanide reversibly binds to the ferric ions cytochrome oxidase three within the mitochondria. This effectively halts cellular respiration by blocking the reduction of oxygen to water.

Would this apply to creatures there or is there some way to prevent it or similar things from happening?