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ETpro's avatar

Is there life as we don't know it?

Asked by ETpro (34208 points ) October 15th, 2013

Whenever we talk about what extraterrestrial locations might support life, we speak of places with conditions that would suit life “as we know it.” Why limit it to that? Hasn’t nature shown us often enough that it’s far more creative than we are. It seems to me that in suggesting that life elsewhere has to fundamentally match life on Earth, we’re stretching the anthropic principle much further than it was ever meant to go. Even here on Earth, there are extremophiles that challenge our common understanding of what life can and can not tolerate. Even here, things live miles under the Antarctic ice cap, 8500 feet down in granite bedrock, and in volcanic hot springs filled with boiling sulfuric acid.

And all these extremophiles evolved from original single-cell organisms that came into being to fit a place exactly like Earth. With sufficient chance arrangements, why couldn’t complex carbon molecules get arranged in different ways to take advantage of conditions prevailing on a gas giant like Jupiter, with its atmosphere rich in ammonia crystals, water vapor, and organic chemicals including methane. The Jovian atmosphere produces lightning 1,000 times as powerful as what we experience on Earth. As it flashes through the dense cloud layers covering Jupiter’s core, might it not drive weird chemistry. How can we be so sure that the conditions on Jupiter, or any other carbon rich planet for that matter, are not exactly right for the formation of life as we DO NOT know it?

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6 Answers

drhat77's avatar

Arthur C Clarke and Kim Stanely Robinson and Larry Niven have all theorized about noncarbon based life forms.
If we come to a planet that has them we may just step on them as we examine the geology.
The singularity may create computer based life forms on this planet shortly.
That’s my 3 cents on it.

Kropotkin's avatar

Extremophiles have adapted to extreme conditions, but when it comes to the genesis of life, all we have are DNA molecules, and extremophiles are still our DNA-based cousins.

What I’m trying to get at is that the transition from chemistry to biology is likely restricted by physics—that is, the evolution of matter to simple self-replicators and to more complex cellular life may well be more constrained than the later adaptation of life to its environment, thus limiting the possible types of geneses and the environments in which they can occur.

One simple likely requirement for abiogenesis is a stable physical substrate, which I’m not sure exists on a gas giant like Jupiter, with its chaotic and swirling atmosphere.

I suspect the anthropic view, or the Earth-like chauvinism may be the correct one. It may be that the genesis of life itself can only occur on Earth-like planets. It may be that self-replicating molecules are somehow mathematically elegant (like a hexagon is for a bee’s nest) and physically efficient in only a limited number of ways, and there is a sort of path of least resistance toward life which can only occur within particular physical parameters.

I do not deny that once life is underway that it can adapt to various extremes, but this says nothing about where life can start in the first place.

flutherother's avatar

Not only can we not imagine the forms of life on other worlds but we can’t even properly imagine the forms of life on this world. Whales equal oil, elephants equal ivory is about as far as we get.

ETpro's avatar

@drhat77 I suspect that we’ll find all life forms to be carbon based simply because carbon is so adept at forming bonds in multiple ways to itself and to other elements. Silicon is second in this capacity, so if there is any life that’s not carbon based, it might be silicon based, but I will be very surprised if we meet any walking sand dunes or living, breathing beer bottles. :-)

@Kropotkin Since we have no idea how abiogenesis occurred, it seems a stretch to use it as an argument for life needing Earth-like conditions. Some scientists now think it may have first occurred around hydrothermal vents on the ocean floor. If that’s true, then we are the extremophiles of life and the stuff that lives in boiling acid is normal. Other scientist wonder, having found complex precursors to life on space rocks and in comets, if life even formed here. It may well be it did not. If it first formed somewhere else, and that source seeded the early Earth, we haven’t a clue what conditions if formed under. What’s more, even if we knew the initial conditions for abiogenesis here, that says nothing about those conditions being the only ones the process could employ.

@flutherother How sadly true. To our credit, not all of us think like that.

ragingloli's avatar

How would you know that there is life as you do not know it if you are unable to recognise it as life as you do not know it even if it were in front of your own eyes

Kropotkin's avatar

@ETpro That wasn’t exactly my argument. I think it is a truism to state that there are physical constraints on the type of chemistry needed to produce life, and the question that follows is whether those constraints are relatively broad (exotic and unimagined life beginning in a wide range of conditions with very different chemical compositions and conditions), or a narrow range (conditions similar to the early Earth, but not necessary just Earth, and with or without extraterrestial seeding, for example.)

I suspect that possible geneses falls nearer toward the constrained range. That the required conditions to go from chemicals to life are likely more restricted, and that this restriction on how life can begin at all in the first place is a facet of physical laws. So, even though carbon may be adept at forming different complex bonds, only a few of the configurations are actually useful for evolving or forming self-replicating molecules.

Just to emphasise. I am not making any sort of confident claim here. Your question invites speculation, and thus I offer my speculation—it just happens to contradict your more optimistic thesis.

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