I've been doing some research, and have collected the following list of forms for life to take: Normal carbon based aerobic respiration, which occurs on Earth. Hydrogen Sulfide based forms. This occured on Earth but was generally replaced by aerobic forms. Chemautrophs - Organisms which derive energy from the decomposition of organic molecules. All earth organisms metabolisms are derived from this in some way, but I was imagining a system dependant entirely on this kind of metabolism. Ammonia based - Replaces the role of water with ammonia. Would either be high pressure or low temperature environment. Silicon based - Replaces the role of carbon with silicon. Probably wouldn't be aerobic since silicon dioxide is a solid, and not easily expelled, where carbon dioxide is a gas, and is thus easily expelled. Artificial - Computer based life forms, what I call "secondary life" since it is created by a preceding form directly. Nebulaic - Derived from dust in nebulas. I would classify any organism capable of living in the comparitive vacuum of space as Nebulaic. Plasma - Some research has shown the ability to create primitive cell structures from plasma. It is not inconcievable that life forms would then evolve on stars, magnetospheres, or even ball lightning. Living Planets - Think Solaris. In some (inconcievable?) manner, a planet becomes alive. I don't know how it would reproduce. The strong Gaia theory would be a lesser degree of this. Core - Life living in the molten mantle or core of a planet. Neutron Star - A system where life is formed on the surface of neutron stars, from highly packed 'nuclear molecules'. Something like this would help populate the universe which is on average quite hostile to human life. I especially like the idea of intelligent planets. Are there any others that I may have missed? I left out some I don't find particularly useful or likely, such as noncorporeal. What kind of impact would these kind of different life forms have on an exploratory game? Life forms on Neutron Stars, for instance, would be difficult to meet, and so their usefulness in gameplay is limited. (Not to mention they probably live on a much faster timescale than we do.) I'd like to be as exotic as possible, without removing from gameplay. Would having aliens which cannot be interacted with directly be frusterating? Many of the biological systems are poisonous to another. (Water would be poisonous to Ammonia based life forms). Which are all the varieties possible? Can carbon based Ammonia life forms evolve?

Quote: Original post by Numsgil
I've been doing some research, and have collected the following list of forms for life to take:

I'd like to be as exotic as possible, without removing from gameplay. Would having aliens which cannot be interacted with directly be frusterating? Many of the biological systems are poisonous to another. (Water would be poisonous to Ammonia based life forms).

Which are all the varieties possible? Can carbon based Ammonia life forms evolve?

You can get away with almost anything for life forms, depending on how 'hard' you want your sci fi background to be. I'll go through the suggestions so far and give them a mark out of 10 according to how believable I think they are. (10 means believable in a hard sci fi background, 1 means not very believable, best kept to a sort of soft, sci fantasy setting)

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Normal carbon based aerobic respiration, which occurs on Earth.

Hydrogen Sulfide based forms. This occured on Earth but was generally replaced by aerobic forms.

Chemautrophs - Organisms which derive energy from the decomposition of organic molecules. All earth organisms metabolisms are derived from this in some way, but I was imagining a system dependant entirely on this kind of metabolism.

Ammonia based - Replaces the role of water with ammonia. Would either be high pressure or low temperature environment.

I'm not sure how feasible the ammonia based life forms are, but they sound reasonable for a life form developing in 'the correct' conditions, so I'll give these an 8. The others are based on existing, known forms and mechanisms, so they get a 10.

Quote: Silicon based - Replaces the role of carbon with silicon. Probably wouldn't be aerobic since silicon dioxide is a solid, and not easily expelled, where carbon dioxide is a gas, and is thus easily expelled.

Chemically speaking, silicon makes a poor substitute for carbon due to it's inability to form such complex molecules. However, you could probably ignore this and suggest that in 'certain conditions' silicon based life can develop, without danger of sounding too improbable, so I'll give silicon life a 6.

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Artificial - Computer based life forms, what I call "secondary life" since it is created by a preceding form directly.

I don't think these are at all unbelievable. 10.

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Nebulaic - Derived from dust in nebulas. I would classify any organism capable of living in the comparitive vacuum of space as Nebulaic.

My first thought is that it seems rather unlikely that life would ever develop in a nebula. It's still too diffuse for the chemical reactions required to form the basic building blocks of life with any reasonable probability. What would they eat? How would they respire? I give these a 3 because there doesn't seem to be any plausible ecology.

Quote: Plasma - Some research has shown the ability to create primitive cell structures from plasma. It is not inconcievable that life forms would then evolve on stars, magnetospheres, or even ball lightning.

I've not heard about this. Are you sure you're thinking about the correct usage of 'plasma' and 'cell'? These words are used in a lot of different ways. For the time being I'll give these a 3, although the idea of 'energy based' life forms has been around for a while, I don't really consider them to be 'hard' sci fi.

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Living Planets - Think Solaris. In some (inconcievable?) manner, a planet becomes alive. I don't know how it would reproduce. The strong Gaia theory would be a lesser degree of this.

I'm not too sure about the idea of the planet itself being alive, I can't think of any remotely plausible mechanism for something like that to come about, unless it was created as n artificial life form. So this gets a 1 if you're suggesting it developed naturally, or a 10 if it's an artificial planet. The Gaia planet idea is quite interesting though, I'll give that a 5.

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Core - Life living in the molten mantle or core of a planet.

I suppose this depends on the planet... if it's an ice planet such as Europa, then the molten core is just water, which is actually a very good candidate for recognisable life, and I'd give this a definite 10. If you're thinking more along the lines of a rocky planet, it'd be lower... perhaps one of the more exotic forms of life might be able to develop and survive down there, so I'll give it a 4.

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Neutron Star - A system where life is formed on the surface of neutron stars, from highly packed 'nuclear molecules'.

I'd say this is the least plausible so far, so I'm giving it a zero. I don't see how you can build anything complex enough to call life out of nothing but densely packed neutrons.

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Something like this would help populate the universe which is on average quite hostile to human life. I especially like the idea of intelligent planets.

Are there any others that I may have missed? I left out some I don't find particularly useful or likely, such as noncorporeal. What kind of impact would these kind of different life forms have on an exploratory game?

What about life forms on gas giants? They might be composed of bubble like cells, with liquid membranes separating their internal gases from the outside. Very fragile of course - a large enough change in pressure or contact with something solid might cause them to pop.

Quote: Original post by Sandman
My first thought is that it seems rather unlikely that life would ever develop in a nebula. It's still too diffuse for the chemical reactions required to form the basic building blocks of life with any reasonable probability. What would they eat? How would they respire? I give these a 3 because there doesn't seem to be any plausible ecology.

Yes, I agree that it seems unlikely. This site indicates that it is atleast feasible. My largest issue with this would be making it work in a game.

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I've not heard about this. Are you sure you're thinking about the correct usage of 'plasma' and 'cell'? These words are used in a lot of different ways. For the time being I'll give these a 3, although the idea of 'energy based' life forms has been around for a while, I don't really consider them to be 'hard' sci fi.

I was surprised when I read this too. It's apparently brand new research (about a year ago). I read about it here. This would be interesting in that I could create life forms which live inside stars, although I'd have to research it more to figure out which stars should create this kind of life.

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I'm not too sure about the idea of the planet itself being alive, I can't think of any remotely plausible mechanism for something like that to come about, unless it was created as n artificial life form. So this gets a 1 if you're suggesting it developed naturally, or a 10 if it's an artificial planet.

I think an artificial planet would be the best. It would give this concious / alive planet a purpous, perhaps as a way for a sentient race to communicate with the planet to find immenant earthquakes, etc.

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Neutron Star - A system where life is formed on the surface of neutron stars, from highly packed 'nuclear molecules'.

I'd say this is the least plausible so far, so I'm giving it a zero. I don't see how you can build anything complex enough to call life out of nothing but densely packed neutrons.

My initial reaction too. I 'borrowed' the idea from here. I'm not sure useful gameplay could be created from such a race, though.

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What about life forms on gas giants? They might be composed of bubble like cells, with liquid membranes separating their internal gases from the outside. Very fragile of course - a large enough change in pressure or contact with something solid might cause them to pop.

Gas planets tend to have very chaotic winds. Wouldn't any life forms which managed to evolve on a gas planet be very robust? Or perhaps just very elastic.

Thanks for the input Sandman.

What about some form of life that evolves using a large amount of metals?

I don't know how feasible it is, but it seems that a system very rich in metals (old core systems) would evolve a form of life that utilized that resource.

Depending on your game, you often seem to get a separation between 'universe' and 'gameplay', the gameplay obviously occurring within the universe. (It's a truism, therefore that the universe must always be bigger than the gameplay.)

Most genres (i'd say most noticably first person shooters) tend to have a universe no bigger than the gameplay. RPGs on the other hand tend to have a bigger universe, which the player perhaps sees when an NPC makes a vague reference to 'The Last Stand of the Three Followers on the Cutlass Coast'. Knowing your world this well helps add depth to events and create horrifically intertwined plots ;)

It can be worth fleshing things out more than you need. It can make your universe seem more solid. It's also fun. Only spend the time if the game will benefit (perhaps it helps maintain your interest?) though!

MOST life on earth is sun-based for energy or based on another source that gets its energy from the sun or based on another source which is based on another...you get it...

but you forgot one type of life which IS a reality...

you guys know about the deep ocean vents? they have ecosystems that have absolutely NOTHING to do w/ the sun...

you might want to include those, even though they are limited to bacteria and simple "plant"-like things at the moment...

-Ajain

Quote: Original post by Ajain
MOST life on earth is sun-based for energy or based on another source that gets its energy from the sun or based on another source which is based on another...you get it...

but you forgot one type of life which IS a reality...

you guys know about the deep ocean vents? they have ecosystems that have absolutely NOTHING to do w/ the sun...

you might want to include those, even though they are limited to bacteria and simple "plant"-like things at the moment...

-Ajain

As I understand these ecosystems are fuelled by the sun indirectly. They gain most of their energy from the hot vents which are in turn heated by the earth's core which is heated by the sun.

IIRC these ecosystems are entirely based off of Hydrogen Sulfide reactions, which he noted as the second item on the list.

Quote: Original post by Anonymous Poster

Quote: Original post by Ajain
MOST life on earth is sun-based for energy or based on another source that gets its energy from the sun or based on another source which is based on another...you get it...

but you forgot one type of life which IS a reality...

you guys know about the deep ocean vents? they have ecosystems that have absolutely NOTHING to do w/ the sun...

you might want to include those, even though they are limited to bacteria and simple "plant"-like things at the moment...

-Ajain

As I understand these ecosystems are fuelled by the sun indirectly. They gain most of their energy from the hot vents which are in turn heated by the earth's core which is heated by the sun.

IIRC these ecosystems are entirely based off of Hydrogen Sulfide reactions, which he noted as the second item on the list.

The earths core is heated by radioactivity from itself...there are convection cells caused by the breaking down of various elements giving off heat...these cells can burn through the crust and then then crust moves over these and there are basaltic volcanoes where they are (EX: hawaii)...

the earths mantle is liquid iron, nickel, and small amounts of radioactive materials...when the radioactive materials finish breaking down and stop producing enough heat for the mantle to be liquid (the [inner] core is solid...and actually has anommalies so it flips [evidence: the sea is split and at the mid-ocean ridge htere is a constant flow of magma...when it dries the metal {usually iron} aligns with the earths current magnatism so we see bands of different polarity] and during a short period of time there is no magnatism and the earth is subject to the sun's raw radiation because the magnatism doesn't funnel it to the poles [causing the arora borialis] when there is no magnatism...the outer core is liquid but I don't know much about that) the earth will turn into a planet similar to mars [which DID either have liquid water, life, or both...we have non-conclusive evidence for both] where raw radiation will bath the planet long enough that all the liquid water vaporizes, the life is poisoned, and the remaining water is frozen at the poles...

(that last paragraph was a bit confusing...)

if there is one thing I can defend myself on it is the mantle/core/crust...I just had this stuff in science...All of this was written off the top of my head so I am sorry for any typo's...look up any of the info in here to see if it is true yourself...I'm not sure if all of it would be on the internet but probably...

so there IS life that is completely non-sun dependant...if the sun were to dissappear or callapse on itself (both of which are almost impossible) our life would die because of starvation...not to mention that the earth would lose a ton of its heat rapidly but this life would go on at the hot vents as long as the earth has a liquid mantle...

-Ajain

Quote: Original post by Ajain
look up any of the info in here to see if it is true yourself...I'm not sure if all of it would be on the internet but probably...

-Ajain

Here is a Clicky to help you defend yourself against the google impaired.

There are a lot of interesting links in there too.

Yes, I realized that life can form any where there is a heat source, medium and heat sink (I think. Perhaps there are counter examples).

That's where I got the idea for a lifeform living in the convection currents of a mantle of a rocky planet. I think I might have read it somewhere too... Can't remember.

Are there any mediums that I may have missed that might produce life forms?