Is there life on other planets which uses something other than oxygen to survive?

Question

Why do most people (including scientists / physicists) use the base that there might be life on other planets where there is oxygen? Isn't it possible that there is life on other planets which uses something else to survive like carbon-di-oxide or any other element?

Can it not be possible to have life in terms of creatures where they don't need oxygen or any other bi-product of oxygen? Can "beings" on other planets be of a mechanical sort (e.g. robot kind)? I agree that living beings (as far as our knowledge goes) need oxygen in some form or the other to survive. But is there a possibility where there can be "life" with a different element required to survive?

Answer 1

Most of the periodic table is not very useful to try to design a complicated organism, as far as we understand chemistry and life, i.e. most of it is metals.

Also, to build the complicated molecules which could serve as a basis for life, you probably need to start with atoms that can have multiple bonds. In our case, this usually means carbon, nitrogen and oxygen.

There used to speculation that the elements in the same columns of the periodic table but one row down might be able to serve the same functions, namely silicon, phosphorous and sulfur. However, no one has really developed a thorough understanding of how this might be possible, and so I think mostly this speculation has fallen by the wayside.

Your extra question is a bit hard to understand, but I think you are asking why scientists believe that the presence of molecular oxygen would be a marker for life on another planet. I think this is because oxygen is so reactive that it is bound up in other compounds as a planet forms. It could only be released in large enough quantities to detect from earth if it was being released by a living process that replenished the O2 in the other planet's atmosphere.

BTW: carbon dioxide has oxygen it in; on earth, it is largely a by-product of an oxygen utilizing biochemistry or chemistry (i.e. respiration and fire). And, of course, all the carbon in our bodies probably started as CO2 ... it was taken up by plants and made into sugars which were made into other molecules.


Edit:
Plants use CO2 to make sugars, but they need oxygen to live. If you put a houseplant in an oxygen-free environment, it would die.

There are organisms that live with out oxygen on earth, but they are mostly bacteria as far as I know.


Edit2:

It is difficult to answer your question because your profile doesn't make it clear how old you are or what level of education in physics and chemistry you have. But I'll try some more.

Scientists have been thinking about this for at least 50 years ... people with Ph.D.s, tons of knowledge, and genius IQs. The answers they have reached are not limited by imagination = they have certainly tried to imagine life without oxygen, for example. The answers they reach are limited by the rules of physics and chemistry that govern the universe, and by what is necessary for life to begin. It isn't enough to just say "couldn't it be this way too?", one has to take into consideration how the universe can actually work.

So, for example, life has to be made out of building blocks that can be produced by natural non-living chemical processes, it has to be self-organizing, able to reproduce itself precisely, able to make more complicated constituents and break them down. It needs a way to separate the interior living part from the exterior non-living environment (a cell membrane) and it needs a way to move nutrients across this separating barrier. Life needs a liquid environment so that nutrients can be carried to and from the cells by diffusion and so that chemical reactions can occur. And so on.

There are only a few kinds of chemical compounds that seem to be capable of doing these things: proteins, nucleic acids (DNA and RNA), lipids (fats) and soaps, amino acids (from which proteins are made), and so on. All are based on carbon (C), nitrogen (N), oxygen (O), hydrogen (H), and a few other elements (S, P, etc.). Do you know the periodic table? It is a list of all the elements that can be found in the universe (see it here: http://www.corrosionsource.com/handbook/periodic/ ). Everything is made from them. And most of the ones that can be used to make a living system are the ones in the upper right area.

As far as scientists can imagine, within the limits imposed by the physical and chemical laws that operate in the universe, most of the elements found in the universe cannot satisfy these requirements. As I mentioned, most of the periodic table is made up of metals ... and there seems to be no way that metals can self organize into cells that have a metabolism, reproduce, etc. Keep in mind that metals are only rarely found free in the environment = they are usually ores. That is, they are usually rocks that need to be melted and processed in order to make the metals you see. And no one thinks that rocks are somehow alive or capable of producing life. So, just based on the nature of the universe, the people with genius IQs who study these issues their whole lives probably would say that it is not possible for some sort of metallic robot life to have arisen and evolved.

Another example: since it is expected that primitive organisms will need to exist in a liquid environment so that nutrients can diffuse to the cells and wastes diffuse away, what liquids can accomplish this? As far as I know, the only liquid that can do it effectively is water, H2O. So scientists think that for life to arise, there must be liquid water. Nothing else can adequately carry the molecules - without destroying them - that would need to be present to allow self organizing chemical processes to begin.

As I said above, in the past (the 1950s - 1970s), scientists used to think that sulfur might be able to substitute for oxygen, and that the solvent could be H2S, instead of H2O. But in order for that to happen, a planet would need to be at much higher pressure than earth, and this would probably mean much higher temperatures, and then the other chemicals necessary for life to begin would break down, and so on. So, it is liquid water only that can act as the solvent, and that means life can probably only arise on worlds of a certain temperature, and size. It is chemistry and physics.

With regards to oxygen in particular, as I mentioned plants take carbon dioxide out of the air and make sugars. In short, what we do is that we literally burn those sugars in order to make energy. And burning takes oxygen - that is why we, like fires, release carbon dioxide.

So, if you want to design a metabolism using something other than oxygen, you need to figure out a way to transfer and release energy that doesn't use oxygen, can be dissolved in water, can cross cell membranes without destroying them, can be made from the chemicals that would be found on a newly formed planet, and so on. The only thing I can think of is nitrogen, perhaps. But I am not an expert, so maybe there are physical or chemical limitations to nitrogen that make it utterly impossible that it would be usable as an energy source. So, if that is ruled out by the experts, and many other possible chemistries are too, then maybe O2 is the only thing that will work as fuel for complicated lifeforms, anywhere in the universe. CO2, as you are probably aware, puts out fires - meaning that it cannot support 'burning' either inside a cell, or outside in the environment. Nitrogen also puts out fires, by the way.

As I said, really smart people have been thinking about this and doing experiments for decades. I am not one of them, so I may not be totally correct here. If you are seriously interested, though, I am sure books have been written all about these things - maybe dozens or even hundreds of books. Perhaps you can find some through Amazon or someplace and read up on the specifics.

Hope this helps. Good luck!

Answer 2

Due to the fact that even on our planet, we are still finding life forms that were never before known. I believe there is more out there in space than we could ever imagine. And the possibility of different species breathing as we do or in any other way is more realistic then most scientist or religious persons would care too admit.....

Answer 3

Of course, there is possibility. Even on Earth we discover life forms that brings us an amazement and confusion. It is clearly possible that there are "life" forms in outer space that live on something different than Oxigen or have an ability to create oxigen from other chemicals by chemical reaction inside their own "organs".

Answer 4

The answer: it's possible. We already know that plants on our planet use carbon dioxide to survive, so why can't other life forms?

Answer 5

Absolutely possible; there are things right here on Earth that DIE when exposed to plain old oxygen, lol. So its absolutely possible to have life in an oxygen-free environment. Dunno about the intelligence level of it, but sure, its possible.
Though I'm now uneasily envisioning a planet full of intelligent salad....hmmm....yummy....

Answer 6

Carbon Dioxide is deadly to US. But it might be the other way around for other lives. So it is possible to live on other substances.

Answer 7

We have some weird anaerobic life on Earth that doesn't need free oxygen to live.

Beyond that -- we also have software-based life.

Answer 8

thats a good theory.

why would aliens be like humans where they need oxygen?

sometimes i think that aliens are the same as humans but they were'nt put on earth

Answer 9

Yes it could be possible like the plants that they need CO2.