What conditions enable life to exist on another planet?

[Mackay1011]

What are the main things that are needed for life to exsist on another planet, or can micro bacteria or whatever just adapt to heat, cold, water, ect, what was on our planet when we first came about?

 

[SpitfireAce]

well... as we look at extra-solar planets, the vast majority have very elliptical orbits (which are favored over highly circular orbits), our almost circular orbit seems to be a statistical anomaly... so perhaps some form of stability... in climate, or radiation seems to favor life... (unless its just a giant coincidence and all those planets have life too)

also, life on Earth is water based... so we look for water.. it is doubtful that life could substitute some other substance for water because this substance would probably be found on Earth and in that case we should find life in places with 0 water like deep underground, but we don't

it also requires a somewhat huge localized decrease in entropy, which would require a lot of energy or a vast period of time to occur

lightning, rain, hot rocks... to synthesize the basic stuff like amino acids

perhaps a moon

 

[Danger]

For life as we know it, as Spitfire pointed out, the requirements are carbon, oxygen, and water. There's nothing to prove, however, that other life can't be based upon other materials.
Places that you would probably consider the most inhospitable environments on Earth host a surprising amount of life, such as sea-floor volcanic vents. That's an incredibly high-pressure, high-temperature situation with a sulphur 'atmosphere', and yet things thrive there.
It would also depend upon how you define 'life'. Things like simple amino acids are perfectly capable of surviving in open space. That's a building block of life, rather than life itself (by my definition), but it shows the potential that organic compounds can adapt to a lot of different circumstances.

 

[Mackay1011]

Thanks for the comments, when i say life i mean anything that can move and reproduce in any form. so for any planet to sustain life of any kind HAS to have carbon, oxygen and water.
cant you have argon carbon and water for example? what's argon anyway lol

 

[BoomBoom]

so for any planet to sustain life of any kind HAS to have carbon, oxygen and water.
cant you have argon carbon and water for example? what's argon anyway lol

Argon is a noble element that does not react with anything and has no function within life. Saying that oxygen and water are required is redundant since water conains oxygen. So I would say minimum required elements would be water and carbon and perhaps nitrogen since it is fairly abundant in many amino acids and such.

 

[Danger]

Saying that oxygen and water are required is redundant since water conains oxygen.

True, but I was referring to oxygen that isn't bound to hydrogen, so as to be breathed or combined into carbon dioxide for plant respiration.

 

[Moridin]

As we have not found any life on other planets, it is hard to speculate on what it would be made of. The best we could do would be to compare with ourselves, but that it not enough.

Well, as far as we know life requires carbon, but that is not necessarily correct. It is the physical and chemical properties that make carbon ideal for life, but under other circumstances, it might be different. A substance that has similar properties is silicon, for instance.

Oxygen might not be needed as well, since there are bacterial life here on Earth that would die in oxygen rich environment. They get their energy from oxidizing sulfur or iron, I think.

If there is life in the Universe, besides us, they do not have to be complex organisms. They could just as well be unicellular organisms. It just so happens that water is part of the cellular respiration here on earth, but in other environments, who knows?

 

[Danger]

Oxygen might not be needed as well, since there are bacterial life here on Earth that would die in oxygen rich environment. They get their energy from oxidizing sulfur or iron, I think.

And just how would they oxidize something if they have no access to oxygen?

 

[BoomBoom]

And just how would they oxidize something if they have no access to oxygen?

Do the extremophiles that live in the deep oceans of Earth near volcanic vents have access to atmosphereic O2? They do not and metabolize things like frozen methane. Life is really quite adaptive and can live in a wide assortment of different environments.

I kind of agree with Moridin in a sense. Given a completely different soup of chemicals, who knows what form life would take. But based on life on Earth it would seem you must have carbon. I can't wait until we find something and hope it happens in my lifetime.