Why is this generally thought?

[AlkalineGamer]

Obviously i'm not an expert on the matter, so am partially talking from where the sun don't shine, but as far as i understand, it is commonly believed by scientists that water is required for life. And that if a planet has no water, then it is highly unlikely to be a candidate for life.
Whilst true for life here on earth, why should it be so for all life everywhere? We formed from acidic pools of standing water, but why can't other life forms be created from other substances.

Please if there are any scientific innacuracies, please either ignore me, or (politely!!!) correct me.

Obviously water is important for us, it's our life-source without it we die. But we grew and evolved on a planet where water was very abundant, why wouldn't we use it as a life source.
Surely on another planet with similar conditions, but with different chemicals, life could still form.
It was once believed that all life forms where made from 6 basic substances, Carbon, Sulphur, oxygen, hydrogen, nitrogen and phosphorus. yet not long ago a bacteria was found that replaced one of these elements with arsenic, considered our natural poison.

So why can't the same go for water, if creatures can be made from something considered lethal to all living things, then why can't things live without something considered vital for all living things?


Not sure if this is already some sort of scientific debate or not, if so then could someone be kind enough to link me something.

 

[RatRace123]

I think when they talk about water being required for life, they're talking about life similar to us, or just talking about us.
Half the time when they're talking about life on planets, they're referring to planets that could support us living on them as much as finding new lifeforms.

 

[Vern5]

Scientists rely on the observable facts of the universe to form their opinions, otherwise they just be normal blokes with ideas like you and me. Honestly, I believe there are chances that there's another planet lightyears away where every last creature on it has to eat a kind of nutrient-rich sand in order to survive. But, hey, I can't prove it, so what would be the point of expressing that opinion in the scientific community.

Overall, the average scientist tends not to be very imaginative. We could debate this idea of non-water based survival until we both died in the argument and wouldn't get anywhere conclusive unless we could find observable data on non-water based survival.

 

[C.S.Strowbridge]

You need a liquid for chemicals to move around in for them to react. That's why in chemistry you will deal with a lot of reactions in an aqueous solution. Technically you could have these reactions take place in any liquid, but water has added benefits. It expands when it freezes, for instance, and the resulting ice is a weaker conductor of heat. Therefore, bodies of water don't freeze solid as easily as a body of another liquid would.

 

[Jakub324]

I agree that there are inevitably life forms that can live on a world that's basically a planet sized Sahara desert, but I'm hardly a scientist, so I may be wrong.

 

[Heronblade]

Water is one of the main things we look for in our search for other life for two reasons:

-It is required for the only type of life we KNOW can exist. We can theorize about other kinds, but until discovered/created, it is only speculation.

-Water is also an excellent medium for lifeforms to use. It is one of only a handful of naturally forming liquids that will mix with and transport a huge percentage of other types of material WITHOUT chemically altering them.

In short, we do think that there is a possibility of life forming without water. But based on the information we have, we are far more likely to find ET life that relies on it than not.

 

[Woodsey]

Don't know, I've thought the same thing.

Perhaps they simply focus on those planets most similar to ours because we know there's a higher chance of them having life.

 

[emeraldrafael]

Probably cause they mean us to populate and live on. There's examples here on earth where creatures dont need water to live. True, they're bacterial, but they exist, and could evolve to something. And this has opened the eyes of science to planets that may have life on them similar in development to said bacteria on earth.

Mainly though, scientists are saying life cant exist on planets without water, but more they want to find one that does, because that means that maybe humans could survive there, or that the inhabitants could be like us, and we would be able to cooperate and live together more easily.

 

[Bara_no_Hime]

You need a liquid for chemicals to move around in for them to react.

Huh.

So... for the sake of argument... would it be possible for some sort of rock-based lifeform to form in magma? That's liquid rock, so chemical reactions could occur. Also, the internal planet heat keeps the mantle from cooling into solid rock, so that's sort of similar to your statements about ice (where the crust is similar to a layer of ice).

That's kinda neat. ^^

 

[Knuxxx]

I think they need to either expand or specify what they mean by "life". Usually it refers to organic life, I'm sure there's other non-organic life out there that doesn't require water or little, if any at all

 

[Erana]

Water is one of the main things we look for in our search for other life for two reasons:

-It is required for the only type of life we KNOW can exist. We can theorize about other kinds, but until discovered/created, it is only speculation.

-Water is also an excellent medium for lifeforms to use. It is one of only a handful of naturally forming liquids that will mix with and transport a huge percentage of other types of material WITHOUT chemically altering them.

In short, we do think that there is a possibility of life forming without water. But based on the information we have, we are far more likely to find ET life that relies on it than not.

This.

But the "Aresenic-based life" stuff is... well, my sister, currently getting her PhD in cellular biology, explained to me that the method they used to come to the conclusion about this is quite questionable; something about them simply determining the substances in the gel, rather than purifying the DNA and then looking at what it's made of. I'll have to ask her to explain it to me again.
Also, arsenic isn't a very stable basis for life. I wouldn't be surprised at all if people proved this whole affair to be a falsehood.

 

[almostgold]

There actually are other solvents that could be hypothetically possible for life under certain conditions. This link lists them, as well as why water is the only one we know for sure:

http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Non-water_solvents

 

[AlkalineGamer]

You need a liquid for chemicals to move around in for them to react.

Huh.

So... for the sake of argument... would it be possible for some sort of rock-based lifeform to form in magma? That's liquid rock, so chemical reactions could occur. Also, the internal planet heat keeps the mantle from cooling into solid rock, so that's sort of similar to your statements about ice (where the crust is similar to a layer of ice).

That's kinda neat. ^^

That's not entirely what he means.
Water is a very useful transport medium in that it's quite fluid, and is neutral PH wise, also it's polar so other minerals can dissolve into it. Not just that it's useful because it's a liquid.

Also water doesn't conduct electricity, just so ya know.

 

[AlkalineGamer]

Obviously i'm not an expert on the matter, so am partially talking from where the sun don't shine, but as far as i understand, it is commonly believed by scientists that water is required for life. And that if a planet has no water, then it is highly unlikely to be a candidate for life.
Whilst true for life here on earth, why should it be so for all life everywhere? We formed from acidic pools of standing water, but why can't other life forms be created from other substances.

Please if there are any scientific innacuracies, please either ignore me, or (politely!!!) correct me.

Obviously water is important for us, it's our life-source without it we die. But we grew and evolved on a planet where water was very abundant, why wouldn't we use it as a life source.
Surely on another planet with similar conditions, but with different chemicals, life could still form.
It was once believed that all life forms where made from 6 basic substances, Carbon, Sulphur, oxygen, hydrogen, nitrogen and phosphorus. yet not long ago a bacteria was found that replaced one of these elements with arsenic, considered our natural poison.

So why can't the same go for water, if creatures can be made from something considered lethal to all living things, then why can't things live without something considered vital for all living things?


Not sure if this is already some sort of scientific debate or not, if so then could someone be kind enough to link me something.

Science fiction writers often imagine creatures coming from worlds with insanely different atmospheres to our own.

Now I don't think it's that scientists aren't open minded enough to accept this as a possibility. But rather their propensity to deal in fact and reasoning based on facts took them away from this idea.

Most probably do believe it's possible for life to develop that is drastically different to our own. But don't have any sound reasoning as to why.

But wasn't there a microbe found recently that either fed on or breathed arsenic? Found in some American lakes or something.

So now I should imagine most scientists working in a related field do accept it as a possibility.

Yeah, i actually mentioned the Arsenic bacteria in my post.

I understand that they might not search other planets due to the probable waster of resources, but i don't understand why it's still genral consesus to most people that water is nessecary for life.

 

[Serioli]

I think they mean something along the lines of 'obvious (recognisable?) life'. There are theories about other forms of life, science fiction writers have to get their ideas from somewhere!

There's a pretty good programme narrated (also created?) by Professor Hawking that goes into alien life.

EDIT: The series is called 'Into the Universe'. Also deals with fun things like time-travel, speed of light, space exploration etc

 

[Weaver]

Well, the idea is we looked around at what we can see and the only planet with life on it is our own. They then suppose that if we can find planets like our own, the odds of them having life are significantly higher than other planets which aren't terrestrial.

I don't think they flat out deny the possibility of lava monsters through some miracle of evolution, but we may as well look for life where we're more certain it will exist than just chance it all on some random planets.

It's a BIG galaxy out there, narrowing things down can really help.

 

[Brandon237]

Water does not react violently with any of the other main substances needed for life. And when scientists say this, they are referring to the Carbon-based life that we know exists. We don't know of other life.

And one critical thing about water, it expands when it freezes. If it didn't, ice would pile up at the bottom of the ocean until it froze over completely. No LIQUID, No life. Liquid is needed for chemical reactions that form life (Carbon-based, that we know of).

 

[Bento Box]

The idea of water being so important for life comes from a simple breakdown of the chemicals in the known universe. Humans match the make-up of the universe nicely -- the universe breaks down as follows:

1. Hydrogen
2. Helium*
3. Oxygen
4. Carbon

Helium is chemically inert -- it doesn't react with other chemicals or do anything, really, other than make balloons float, or make your voice high (or suffocate you if you do it too much). That makes the break down of life on earth:

1. Hydrogen
2. Oxygen
3. Carbon

...make perfect sense from, if nothing else, a probabilistic standpoint. It doesn't hurt that carbon is effectively the opposite of helium, reacting with every damn thing in every damn way all the damn time.

Carbon is crazy shit.

Edit: Before someone asks "WHAT DO HYDROGEN AND OXYGEN HAVE TO DO WITH WATER BEING NECESSARY FOR LIFE," instead, don't ask that at all, but rather repeat the question to yourself until you're smarter.

 

[Spartan448]

In an episode of the orgional Star Trek, the Enterprise crew encounters Silicon-based life. They didn't need water.

 

[Zantos]

I asked this same question to an astrobiologist not long ago. She told me it was to do with temperature. Because of the hydrogen bonding it means liquid water exists at a temperature which carbon biological reactions occur. Very few other materials have this property, and there are a few other properties of water that make it most suitable for supporting life.

Of course she entertained the idea that under different temperatures other elements could behave as organic carbon and give rise to an entirely new set of organisms, but noone's ever found evidence that under extreme conditions there is another element capable of forming organic-like molecules.

Apparently life in Io's sulphur volcanoes is not likely at all