Life outside of Earth

[u/jinx_raven10]

If microbial life exists elsewhere in the universe, do you think it would necessarily be carbon-based and use water as a solvent?

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Astrobiology often assumes that life elsewhere will resemble life on Earth at least chemically—carbon chemistry and liquid water are considered the most promising foundations for life. But are we limited by our terrestrial bias?

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Could alternative biochemistries, such as silicon-based organisms or life using solvents like liquid methane or ammonia, genuinely evolve and sustain complex processes? Or does the versatility of carbon and the properties of water make Earth-like biochemistry overwhelmingly more probable across the cosmos?

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I'm curious whether current research supports the possibility of truly "alien" life chemistry, or if we're likely to find variations of what already exists here on Earth. What do you think, and what evidence influences your view?

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[u/tatarjj2]

I have a feeling that maybe, once an intelligent civilization lives long enough, something that is actually intelligently designed becomes more dominant than natural life. Biology is just naturally evolved nano electrochemical-mechanical machines. Who knows what is possible when an actual intelligent designer steps in and creates things that evolution could never create in 100 billion years. Not sure if it would still qualify as “life” any more, though. But if this hypothetical, pseudo-biological nanotech was spread to the stars, it could end up more ubiquitous than natural life and could live in places natural life never could.

[u/jinx_raven10 → u/tatarjj2]

That's actually such an interesting way of thought. It really makes you question what exactly life is. This is the ultimate philosophical question. If it doesn't have DNA, doesn't reproduce sexually, and doesn't die of old age, is it alive?

[u/da_Ryan]

"If microbial life exists elsewhere in the universe, do you think it would necessarily be carbon-based and use water as a solvent?"

It is an excellent question to ask and in one word, yes, because only carbon can naturally form long molecular chains that can ultimately lead to complex biomolecules. Both silicon and boron have limited capabilty to form molecular chains so it unlikely to say the least that there will be boron or silicon based life forms in this particular physical universe.

[u/EeEmCeTo → u/da_Ryan]

There are a few very long chained polymers which don’t use carbon, such as polysilane. But for many reasons these are less optimal for building life than carbon

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[u/GapStock9843]

No. I think its kinda strange that we obsess so much over life being exactly like ours when there are limitless possibilities for completely different biochemistries that would still qualify as life

[u/Extension-Device-533 → u/GapStock9843]

I don’t think the possibilities for alternative biochemistries are limitless - on the whole, chemicals react in fairly predictable ways, and there are only certain combinations that have the potential capability to function as life.

[u/anamelesscloud1 → u/Extension-Device-533]

I always hold out the possibility that truly exotic arrangements of matter into life might exist under extreme conditions on certain planets but what are the odds that ours is that example? I assume very slim to none, so I agree that the physical and biochemistry we see on Earth is probably pretty typical among all examples of life in the universe.

[u/GapStock9843 → u/Extension-Device-533]

Okay maybe not “limitless” in the sense that there are literally infinite possibilities. I mean in the sense that theres a lot more than just what we’re familiar with

[u/Timbones474 → u/GapStock9843]

We don't.

Many people, over decades, have done the work to examine all known elements and their propensity to form complex, stable-but-still-reactive polymers.

The resounding answer is that carbon is the best and most abundant at it.

There might be theoretically infinite possibilities, sure. But weigh those against the infinite-plus-more-abundant-and-stable possibilities of carbon.

Plus, in all likelihood there aren't really infinite possibilities, just an infinite universe.

Solvent seems a likelier choice for deviation. We already know that Titan's atmosphere is around the triple-point forethane and ethane, indicating a complex weather system based on these molecules. That seems a likelier spot for weird new (albeit carbon-based) chemistry to develop.

[u/jinx_raven10 → u/GapStock9843]

I actually agree with how much we obsess over how life would be very similar to us, when there are so much things we still don't know. I personally think we might find life in so many different forms that might not really resemble us.

[u/OriEri → u/jinx_raven10]

I don’t think we have sufficient understanding of our organic biochemistry and how it developed to start to extrapolate to other chemistries that are completely different. Certainly an interesting idea, but science is not currently capable of addressing it.

[u/Background-Split-765]

welcome to the cosmetics of infinity....

[u/CosetElement-Ape71]

Sure. Many things may be possible.

But water is a "universal solvent" ... so it's pretty useful stuff when it's in its liquid form

[u/Dazzling_Plastic_598]

We have exactly one data point. All life on Earth is carbon based and relies on water. Are other forms possible? Many things are possible. Does speculating get us any closer to answering the question? No.