What colors might an alien's blood be?

[FungusForge]

Humans have red blood as I'm sure most of you are aware, there's also Horseshoe crabs that have blue blood.

I'm curious though if aliens could potentially have their blood be some other color, like green or yellow or something.

[Bill Phil]

Depends on the elements.

Ours is red thanks to iron. Afaik.

[Tex_NL]

Depends on the elements.

Ours is red thanks to iron. Afaik.

Correct. The oxygen carrier in our red blood is hemoglobin which is iron based. A horseshoe crab's blue blood contains hemocyanin which is copper based. Various earth life forms have evolved other metalloproteins so depending on the available elements other (alien) lifeforms could very well do the same.

Mr. Spock's green Vulcan blood isn't that far fetched after all.

Edited October 17, 2015 by Tex_NL

[Kryten]

Correct. The oxygen carrier in our red blood is hemoglobin which is iron based. A horseshoe crab's blue blood contains hemocyanin which is copper based. Various earth life forms have evolved other metalloproteins so depending on the available elements other (alien) lifeforms could very well do the same.

Mr. Spock's green Vulcan blood isn't that far fetched after all.

You can also have other pigments involved which overwhelm the oxygen carrier. Certain skinks have green blood due to very high levels of biliverdin (the same chemical that makes jaundiced people go yellow); and humans can end up with green blood after overdosing on medications containing sulphide, resulting in sulfhaemoglobin formation.

[Tex_NL]

So very true Kryten, I didn't even think about other components. Of course many things other can and do contribute to the final colour.

Edited October 17, 2015 by Tex_NL

[FungusForge]

...and humans can end up with green blood...

That just sounds creepy.

This has been a very educating experience featuring words I can't pronounce.

[problemecium]

Any color is possible. On Earth we have this, assuming I remembered everything correctly:

- Red in humans

- Clear in antarctic fish

- Light green in arthropods

- And some creature has blue, but I forgot which.

[vger]

"Let's cut him into little pieces and see what color his organs are!"

[fairytalefox]

Guys, I hate to say that but...

tl;dr: The term "alien's blood" itself is (most probably) ridiculously irrelevant. Like, "How many angels can dance on the head of a pin?" level irrelevant.

For those who enjoy reading textwalls in broken English:

There was a Polish dude called Stanislaw Lem who isn't probably that famous outside of ex-Soviet Bloc; but inside, he surely is. He wrote science fiction books. Not that American 'our swords are called blasters, our wizards are called scientists, our fairy tales are called SciFi' sort of bullcrap (sorry, American people), but fiction books of a really scientific kind.

His most famous work is 'Solaris', a 1961 novel about people trying to communicate with a space alien. It doesn't contain much action, it consists mostly of the protagonist's thoughts about what's going on. The book's most vivid feature, in my opinion, is deeply developed setting.

I believe that the book has the most realistic space alien description created by humans ever.

In the book, it took about a hundred years for human scientists to merely realize that this thing is an alien.

Blood, they say. Don't make me laugh. Blood means body. With blood vessels and something like a heart to pump that blood. Which means something like nerves and hormones to control the stuff. Which means something like glands and something like ganglia. Which all is extremely, insanely, overwhelmingly anthropocentric.

In Lem's book, after centuries of studying, it still remains to decide whether or not this thing can count as a body.

Still, it's just a fiction book, created by just a human. As we all know, life is orders of magnitude more deep and unexpected than any book. Even a book written by Stanislaw Lem.

The truth is, we're probably looking at a dozen or so aliens right now. We just don't recognize these things as aliens. Because they are too different from guys in rubber masks we can see in almost every Hollywood SciFi movie.

[kerbiloid]

1. Fe is much more common element than Cu, Cr or V.

An Earth-like planet mostly consists of O, Si, Al, Fe.

So, more chances to meet and use Fe than anything else.

2. Terrestrial non-Fe species are worms, arthropods and molluscs.

I.e. small (except squids and Kthulhu) archaic lifeforms appeared when there was much atmospheric oxygen, with primitive oxygen transport, living mostly in water, with primitive neural system.

So, more probably that reasonable aliens' blood would be based on Fe.

I.e. some kind of brown color.

[CptRichardson]

1. Fe is much more common element than Cu, Cr or V.

An Earth-like planet mostly consists of O, Si, Al, Fe.

So, more chances to meet and use Fe than anything else.

2. Terrestrial non-Fe species are worms, arthropods and molluscs.

I.e. small (except squids and Kthulhu) archaic lifeforms appeared when there was much atmospheric oxygen, with primitive oxygen transport, living mostly in water, with primitive neural system.

So, more probably that reasonable aliens' blood would be based on Fe.

I.e. some kind of brown color.

OUR world is extremely rich in those elements. While that gives us some details to work off of, we should not assume that other potential life-bearing worlds will hold that ratio in the same amounts, or that they will (proportionately) lack the other potential oxygen carriers. Or that it has to be one of those elements at all.

[micr0wave]

Pretty hard to guess without knowing the kind of ecosystem the aliens developed in.

Even here on earth we have lifeforms living at temperatures above 100°C.

So everything is possible, even rainbow colours. All those poor unicorns are probably aliens bleeding to death, noone can say for sure ;p

As someone posted before i can also highly recommend Stanislaw.

[FishInferno]

Who says aliens would even have blood? They probably would be nothing like any life we know of.

[magnemoe]

Who says aliens would even have blood? They probably would be nothing like any life we know of.

Unless they are robots they need some circulation fluid to feed the cells.

Its the simplest solution and therefor the most probable.

[Tex_NL]

When it comes to alien physiology indeed all bets are off. Who knows what they look like. But there are a few simple basic rules any complex, intelligent life form must live by.

Externally it needs at least sensors to observe and appendices to interact with its environment. Internally it will need structures to relay information from one part to another. Light and electric are fast, chemical is slow. And it will need some method of distributing 'nutrients' through its body. Diffusion is an option but will only work on a small scale. Diffusion on larger creatures will only work effectively with extreme differences in chemical concentration. Some sort of circulatory system, like blood, is the only logical option.

[FishInferno]

Unless they are robots they need some circulation fluid to feed the cells.

Its the simplest solution and therefor the most probable.

I'm going to get a lot of heat for this, but who says aliens have to be made of cells? We literally have no idea how nay alien would look, behave, or function.

[kerbiloid]

OUR world is extremely rich in those elements. While that gives us some details to work off of, we should not assume that other potential life-bearing worlds will hold that ratio in the same amounts, or that they will (proportionately) lack the other potential oxygen carriers. Or that it has to be one of those elements at all.

ANY Earth-like planet is extremely rich in Fe just because Fe is the ultimate element of regular thermonuclear synthesis and is accumulated in enourmous amounts inside a star nucleus.

It's one of the most common elements in the Universe, large solid planets are made of O, Si, Al, Fe, Mg.

Also Fe, rather to Cu, is chemically active and is involved in many chemical reactions, while Cu usually gets bound and either sinks down or is dissipated inside other rocky materials. Then from time to time Cu floats up with geothermal plumes and so we can get here and there the spots of Cu which we treat as "copper ore".

Who says aliens would even have blood? They probably would be nothing like any life we know of.

Chemical reactions mean solver. Solver means liquid. Liquid needs to move to dissolve something and to bring it from place to place.

So in any case a biological creation will have a liquid and a devices to move it through its body.

Usually they call such liquid "a blood".

Edited October 20, 2015 by kerbiloid

[fairytalefox]

The only thing we're certain about extraterrestrial life is that it should have some sort of energy cycle. Literally everything else is unknown.

Aliens don't have to get energy from oxidation with oxygen, or even from oxidation at all.

Aliens don't have to have energy cycle based on chemistry. Thermal, mechanical, electromagnetic, sound, nuclear, gravitational, you name it.

Aliens don't have to consist of solid matter. They can be complex combinations of fluid or gaseous streams. They can be complex combinations of neutrino streams bouncing between galaxies. They can be complex combination of anything else that can form complex combinations.

Or they can't. We don't know.

kerbiloid and other iron supporters, think about plants. Despite all your reasons, they don't have iron- or copper-based liquid transportation systems. Smallest of them (I believe) don't have any liquid transportation system at all. Amazing, right? And they aren't even alien plants.

[Cirocco]

The only thing we're certain about extraterrestrial life is that it should have some sort of energy cycle. Literally everything else is unknown.

Aliens don't have to get energy from oxidation with oxygen, or even from oxidation at all.

Aliens don't have to have energy cycle based on chemistry. Thermal, mechanical, electromagnetic, sound, nuclear, gravitational, you name it.

Aliens don't have to consist of solid matter. They can be complex combinations of fluid or gaseous streams. They can be complex combinations of neutrino streams bouncing between galaxies. They can be complex combination of anything else that can form complex combinations.

Or they can't. We don't know.

kerbiloid and other iron supporters, think about plants. Despite all your reasons, they don't have iron- or copper-based liquid transportation systems. Smallest of them (I believe) don't have any liquid transportation system at all. Amazing, right? And they aren't even alien plants.

weeeeeellll not exactly everything else is unknown. This is where the philosophical part comes in: what do you consider "life"?

Is anything that can reproduce alive? Can, for example, information be alive? Because that information cannot exist without a physical carrier. Is the mere ability to form complex patterns enough for something to be considered alive? etc.

to use your example of Stanislaw Lem's novel: you say it takes researchers over a hundred years to determine whether or not a thing is alive. I would counter-argue that they are not really trying to determine whether or not it is alive, but rather they are trying to determine whether or not they should *consider* it to be alive. And, consecutively, whether or not humanity should adjust their notion of "life" in general.

Again, this is very much philosophical stuff, and I'm not very good at philosophy. Personally I don't think life can be determined as a discrete value (as in, you can't say: if it has or does A, B and C it is alive. And if it doesn't have/do those things, it is not). Of course, not having a solid idea of what life is or is not makes it kinda hard to determine whether or not you've found alien life if it does not in any way resemble lifeforms as e know it. But hey, I suck at philosophy so I'm not losing any sleep over the question

[kerbiloid]

...Aliens don't have to consist of solid matter. They can be complex combinations of fluid or gaseous streams. They can be complex combinations of neutrino streams bouncing between galaxies. They can be complex combination of anything else that can form complex combinations...

Then you would define more exactly what you mean as "life".

Usually "life" means some self-sustained system based on cyclical processes.

So, a cobblestone can hardly be treated as a life form because you would not find significant changes in it throughout its existence.

Maybe you can treat a planet as a life being due to geological processes, magmatic plumes, etc. Something like colossal amoeba.

But as you can't interact with it due to different time scales that's a pure philosophical assumption. Even if so, would we stop to dig into its skin or stop to drink its water? No.

Let it be that there are reasonable plasmatic whirls inside a Sun.

But its time scale can vary from milliseconds to million years.

And how to interact with a person which has 400 synonyms for word "unstable dynamical turbulence" but which can't understancd at all what is "tabouret"?

So, those "non-biological lifes" are just pure abstractions for us even if they exist.

So, of course only those beings are prcatically mean, whom you can either eviscerate, or caress.

And the topic title implicitly implicates a biological creature having a blood analog.

Of course, iron matters only if talk about an oxygen-breathing life.

(Which is probably the only possible case for active biological life forms).

Plants of course are alive but they have no neural system or its analogs at all.

They are "less alive" than any worm or bug, if you will.

[KerbMav]

"Let's cut him into little pieces and see what color his organs are!"

[bashir is about to operate on a Vorta, when Jem'Hadar encircle him very closely]

Doctor Bashir: I am a doctor. I'm not gonna harm him.

Keevan: They're not here to protect me. They've just never seen what the inside of a Vorta looks like.

scnr

On a more serious note:

Unless they are robots they need some circulation fluid to feed the cells.

Its the simplest solution and therefor the most probable.

It may look like the simplest solution but it actually brings a lot of difficulties and dangers in and of itself.

Let us assume the alien in question lives on a really wet planet with low gravity that is covered in puddles and its structure is similar to that of a sponge, loosely connected cells with lots of space inbetween, with a more rigid framework akin to our bones but very light and flexible. Nutrients are disolved in the water of its natural habitat and the most common way to absorb and distribute said nutrients in the body of the most lifeforms on this planet is by compressing their own structure to shed the old water, rolling a few meters and expanding again to suck itself full with fresh water. Their metabolism uses water, dissolved nutrients, air and sunlight, as well as in symbiosis with any smaller lifeforms living in the water/sponge-alien - so basically a spongy plant, able to live in carbondioxide rich water or in very wet biomes like shallow mountain lakes.

No blood or circulatory system needed.

Edited October 20, 2015 by KerbMav

[Aanker]

Life needs order, cells established through the bilipid membrane are the most basic elements of order available in organics. And by extrapolation, life does appear to be an exclusive extension of organic chemistry, at least until evidence surfaces that indicates otherwise. The 'carbon molecule' lego box is simply unrivalled.

Let's suppose that life develops through a chain of critical events: A, B, C, D. At the moment we seem to know A (organic molecules are common and widespread throughout the solar system) and D (the earliest forms of life on Earth were simple prokaryotic cells consisting of organic molecules). We can guess our way to B, and have shown the spontaneous formation of nucleotides and other important cell components in experiments. C is largely unknown, although we have some models such as the RNA world hypothesis. Both B and C seem to be organic chemistry exclusive. The Earth is abundant in other elements, yet H, C, O (and N) dominate the biosphere.

Our expectations of life elsewhere should thus reasonably work from the assumption that it will consist of the same fundamental molecules we find on Earth. Until there is evidence that the steps necessary for the formation of life can be completed with other compounds than carbon-based molecules + water, I think the working model in this thread (Fe, Cu... For blood colour) isn't too far off.

As far as blood goes, obviously not all life on Earth has blood. But for intelligence, where a large neural network is required to sustain complex circuits, blood is an imperative. Oxygen cannot diffuse freely more than a few milimetres before the tissue in question needs to rely on blood. Blood itself contains electrolytes, water and energy while generating an osmotic gradient for cells throughout the body. It is also a coolant, which is important for our neatly encapsulated and enclosed organs beneath several layers of fat. And it helps deliver cells, antibodies and peptides of the immune system to locales of infection and inflammation. Blood is supreme.

[fairytalefox]

Yeeeah, now we've managed to boil it down to philosophy

weeeeeellll not exactly everything else is unknown. This is where the philosophical part comes in: what do you consider "life"?

Is anything that can reproduce alive? Can, for example, information be alive? Because that information cannot exist without a physical carrier. Is the mere ability to form complex patterns enough for something to be considered alive? etc.

to use your example of Stanislaw Lem's novel: you say it takes researchers over a hundred years to determine whether or not a thing is alive. I would counter-argue that they are not really trying to determine whether or not it is alive, but rather they are trying to determine whether or not they should *consider* it to be alive. And, consecutively, whether or not humanity should adjust their notion of "life" in general.

Again, this is very much philosophical stuff, and I'm not very good at philosophy. Personally I don't think life can be determined as a discrete value (as in, you can't say: if it has or does A, B and C it is alive. And if it doesn't have/do those things, it is not). Of course, not having a solid idea of what life is or is not makes it kinda hard to determine whether or not you've found alien life if it does not in any way resemble lifeforms as e know it. But hey, I suck at philosophy so I'm not losing any sleep over the question

Man, I so agree with you, I could put my signature under every of these words!

Then you would define more exactly what you mean as "life".

Usually "life" means some self-sustained system based on cyclical processes.

So, a cobblestone can hardly be treated as a life form because you would not find significant changes in it throughout its existence.

Maybe you can treat a planet as a life being due to geological processes, magmatic plumes, etc. Something like colossal amoeba.

But as you can't interact with it due to different time scales that's a pure philosophical assumption. Even if so, would we stop to dig into its skin or stop to drink its water? No.

Let it be that there are reasonable plasmatic whirls inside a Sun.

But its time scale can vary from milliseconds to million years.

And how to interact with a person which has 400 synonyms for word "unstable dynamical turbulence" but which can't understancd at all what is "tabouret"?

So, those "non-biological lifes" are just pure abstractions for us even if they exist.

So, of course only those beings are prcatically mean, whom you can either eviscerate, or caress.

And the topic title implicitly implicates a biological creature having a blood analog.

Of course, iron matters only if talk about an oxygen-breathing life.

(Which is probably the only possible case for active biological life forms).

Plants of course are alive but they have no neural system or its analogs at all.

They are "less alive" than any worm or bug, if you will.

I think it's not exactly right to throw away what you call "non-biological life". I believe it's possible to some extent for some of these theoretical abiological lifeforms to exist close to our temporal, spatial and err... environmental (?) scale. I can't think of any reasonable arguments right now, it's just... all I know about the universe makes me think so. Of course I can be wrong because, as usual, nobody knows nuttin', but who cares, it's just an internet forum, so I'll stick with my point for now.

You also exclude plants from the question because they're not alive enough. This cannot be argued because, again, philosophy.

So the actual question is 'blood of what color creatures we're willing to consider alive have'.

If we define 'alive' as 'something that uses gaseous oxidant carried by a liquid to burn something oxidable and thus gain energy required for this thing to exist', then probably yes, some metal cations would be good enough.

It's just this definition is too narrow for my taste.

Oh man. That problem with a plane on a conveyor belt from the thread next to this one is easier to be solved

[fredinno]

Ok, let's just stick this discussion to Alien animals, ok?

[magnemoe]

Yeeeah, now we've managed to boil it down to philosophy

Man, I so agree with you, I could put my signature under every of these words!

I think it's not exactly right to throw away what you call "non-biological life". I believe it's possible to some extent for some of these theoretical abiological lifeforms to exist close to our temporal, spatial and err... environmental (?) scale. I can't think of any reasonable arguments right now, it's just... all I know about the universe makes me think so. Of course I can be wrong because, as usual, nobody knows nuttin', but who cares, it's just an internet forum, so I'll stick with my point for now.

You also exclude plants from the question because they're not alive enough. This cannot be argued because, again, philosophy.

So the actual question is 'blood of what color creatures we're willing to consider alive have'.

If we define 'alive' as 'something that uses gaseous oxidant carried by a liquid to burn something oxidable and thus gain energy required for this thing to exist', then probably yes, some metal cations would be good enough.

It's just this definition is too narrow for my taste.

Oh man. That problem with a plane on a conveyor belt from the thread next to this one is easier to be solved

Trees has sap who is an equivalent to blood, however with Alien I and probably most other think sentinel creatures not some self replicating chemistry on the borderland of life who existed on earth once before we got cells. If the alien is not an machine it has an energy hungry brain it also need to move around fast enough to not getting eaten and the other constrains.

Blood is an very effective way of moving chemical energy, oxygen and other stuff around.

Aliens will probably not bee to alien, no alien life is hard to imagine, look at the variation on earth.

However any large sea animal will look ours like fish, sharks, wales, and sea dinosaurs looked very similar.

An intelligent tool user will probably follow an human body plan, an dinosaur one or a centaur, no they don't need to look humans.

Low chance for some other solutions like elephants who would be the closest you get to tentacle monsters

Yes its lots of other ideas however they would bee eaten by one of the above as they have low efficiency or can not be scaled up.

- - - Updated - - -

Ok, let's just stick this discussion to Alien animals, ok?

Sentinel or at least advanced ones.