What if Life Wasn't Life to Us?

[Acemcbean]

To clear things up about the title, scientists currently believe that life will only exist on planets with Earth like atmospheres, be carbon based, and be dependent on water. I propose a form of life that would be silicon-based, rely on mercury (the same way we rely on water), and potentially even breath methane. There really isn't anything holding this form of life from existing, but according to Humans, it isn't life! Anyone care to explain if this is actually true, as most of this is just my amateur speculation?

[shynung]

What you've speculated is entirely possible. Life could have been made with other elements than carbon, relied on liquids other than water, and use different chemicals to gain energy and replicate.

I have to point out that this is purely speculative ideas; we haven't seen any alternative forms of life as of now (the first time it is discovered, it'll likely make the front page).

Edited April 20, 2014 by shynung

[KASASpace]

Hmm, most scientists actually agree that only two elements can support life, Carbon and Silicon, primarily because they have the most possible chemical bonds. In fact, more are still being discovered, because it's practically infinite!

However, yes, it does not have to breath oxygen, and drink water, but it has to be able to have something that defines what it is. (DNA)

So, all life forms require something akin to DNA, but not necessarily with Carbon.

[Dkmdlb]

scientists currently believe that life will only exist on planets with Earth like atmospheres, be carbon based, and be dependent on water.

Citation needed.

[Rakaydos]

Define life. There is single celled "life" here on earth that thrive without oxygen, without carbon, without water. However, that life still uses DNA, and is limited to enviroments it can protect DNA from.

One of the reasons a Europa Submersable mission is so appealing, is because all the elements of earthlike life could be there. Free oxygen isnt, but peroxide ice is.

[Brotoro]

There is single celled "life" here on earth that thrive without oxygen, without carbon, without water.

No...all Earth life uses carbon and water.

Edited April 20, 2014 by Brotoro

[MajorSystemError]

A really good Sci-Fi novel, Dragon's Egg, explores this hypothesis...very well done book

http://en.wikipedia.org/wiki/Dragon%27s_Egg

[KerikBalm]

No...all Earth life uses carbon and water.

And all life uses oxygen as well.

I'm not saying it breathes O2, I'm saying it needs the element oxygen

However, that life still uses DNA,

If it uses DNA, then it needs:

CARBON!

Oyxgen

Hydrogen

Nitrogen

Phosphorus

As for what the OP proposed, that specific biochemistry seems unlikely, I doubt any life would use mercury - if for nothing else than the cosmic sparisty of it.

One thing that needs to be considered, is the cosmic abundance of various elements.

You can go down a column in the periodic table, and say that the element has similar properties to the lighter one.. maybe life will be based on that element rather than the lighter one... but then you look at the cosmos, and see the lighter one is orders of magnitude more abundant.

To get a situation where the heavier one is locally more common than lighter one requires some special circumstances*.

Or you need some special circumstances to argue that the heavier one is better than the lighter one.

*one such case is lithium vs sodium, sodium is much more abundant, as stellar nucleosynthesis favors the destruction of lithium and formation of sodium, despite lithium initially being much more common immediatedly after the big bang.

Also, lithium is more reactive - I'm not sure if that is much of a reason, Earth life probably uses sodium instead of lithium because its simply more common.

Still, generalyl speaking, the lighter the element, the more common it is...Realistically, we shouldn't be looking at elements much heavier than Fe (you can't use a fusion reaction to release energy if the products are heavier than Iron. IIRC - if it is lighter than Iron, you can fuse it to make heavier elements, and release energy. If it is heavier than iron, then a fission reaction would release energy), simply based on cosmic abundance.

This still leaves "inverted" biochemistries, where the solvent is non polar (like methane, ethane), and a cell's lipid bilayer membrane would have polar groups in the center, and the non polar side would be on the outside. And similar inversion of polar/non polar regions would occur in the protein analogues...

ie, what they speculate ould be on Titan.

It may not be water based, but I'm pretty sure it would be carbon based.

[kiwi1960]

Been putting this very question to people for years.... I'm 54 in July.

People base their assumptions for life based on life as they know it, Some planets "cannot support life" as it has a methane atmosphere... that is wrong, it cannot support life as we know it... we were born here, we breathe oxygen, but what if life evolved on another planet and it breathed methane?

The surface of Venus is a probe killer... 80 - 90 atmospheres on the surface, but if life were to exist there, it would be short, stubby and have massive bones...

It is arrogance to think we are alone in the Universe, and also fatalistic.

Out of the billions and billions of planets out there, only ONE evolved life? Why not 2?

If you believe in 2, why not 100.... 1000.... a million?

And as for the argument that they couldn't travel here because it would take hundreds, if not thousands of years...

YES.... based on our technology.... what if they had warp drive, or FTL, or wormhole creators?

And they also assume these creatures have our lifespans.... hell, turtles can live for over 100 years..... why not aliens living for 1000 years...

In our loneliness, I suspect we have become very arrogant in our thinking... or maybe, fatalistic, or small minded...

You need to dream, to imagine... what if?

Yesterdays "what if" is today's reality.

[SargeRho]

Actually, life doesn't need Phosphorus. There's a bacterium using Arsenic instead of Phosphorus.

[Kryten]

Actually, life doesn't need Phosphorus. There's a bacterium using Arsenic instead of Phosphorus.

No there isn't.

TL;DR: the original researchers could only test the cell fraction (from centrifugation) that included DNA, RNA, and a few other things. Direct analysis of purified DNA shows no arsenic.

Wordswordswords

[jwenting]

To clear things up about the title, scientists currently believe that life will only exist on planets with Earth like atmospheres, be carbon based, and be dependent on water.

No, they don't. There's however not enough to recognise it elsewhere, so why go looking for something you won't recognise when you see it anyway?

[Seret]

Indeed, scientists have long wondered about alternate chemistry such as silicon for life. They're also very interested in extremophiles that might expand our concept of what life can handle.

When it comes to actually looking it makes sense to first look for the stuff when know exists for certain. We can look fit the speculative stuff later if we strike out looking for Earth-like life.

[KerikBalm]

Actually, life doesn't need Phosphorus. There's a bacterium using Arsenic instead of Phosphorus.

NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO

Please, for the love of all that is right and good, stop repeating this BS.

That was a very very poorly done paper and has been thoroughly refuted.

[sal_vager]

Gentlemen, please relax and politely point out flaws, and link to refutations, don't get too worked up over things

[KerikBalm]

Sal - sorry, I'm just very tired of hearing that stuff. It no doubt comes from "popular science" rags and internet articles written be people without a clue what they were writing about.

Something just really rubs me the wrong way when people act as if they are well informed when they aren't, and those popular science rags are major contributors to it.

That "Science" magazine and NASA published that stinker of a paper just makes me die a little inside...

Been putting this very question to people for years.... I'm 54 in July.

People base their assumptions for life based on life as they know it, Some planets "cannot support life" as it has a methane atmosphere... that is wrong, it cannot support life as we know it... we were born here, we breathe oxygen, but what if life evolved on another planet and it breathed methane?

There are organisms that metabolize methane.

http://en.wikipedia.org/wiki/Methylotrophy

see also:

http://en.wikipedia.org/wiki/Methanogen

Note that in the beginning, molecular oxygen was a toxic byproduct. The buildup of oxygen cause a mass extinction, the oxygen catastrophe. It is well established that you don't need molecular oxygen for life.

You do need the element, for life as we know it. Nothing says that a methane atmosphere precludes life as we know it.

Life as we know it evolved without an atmosphere of molecular oxygen.

The surface of Venus is a probe killer... 80 - 90 atmospheres on the surface, but if life were to exist there, it would be short, stubby and have massive bones...

I'm pretty sure the surface of venus is sterile. There are no plausible complex structures (chemical or otherwise) that would be stable under those conditions, and have access to an appropriate energy gradient.

It is arrogance to think we are alone in the Universe, and also fatalistic.

Out of the billions and billions of planets out there, only ONE evolved life? Why not 2?

If you believe in 2, why not 100.... 1000.... a million?

I don't know of anyone that seriously suggests there are no other planets with life.

And as for the argument that they couldn't travel here because it would take hundreds, if not thousands of years...

YES.... based on our technology.... what if they had warp drive, or FTL, or wormhole creators?

#1) what does them coming here have to do with anything?

#2) Such devices require exotic matter (negative energy), and still may not be possible (ie, physics says no). Please don't use a trite analogy with the sound barrier, the two are not even close to analagous

#3) Hundreds or thousands of years is not much of an argument. Life has been here for 4 billion years... that is 4,000 million years.

If one could travel at 0.2C, one would get from one side of the galaxy to the other in 0.5 million years. With fusion power one could travel that fast, even faster if Busard Ramjets could be made to work. Thus in the geological time scale, the galaxy could be colonized very rapidly.

Even at a modest 0.01C average speed of colonization, if there were thousands of spacefaring civilizations out there, the galaxy would be completely colonized very rapidly.

We thus arrive at the Fermi paradox, one possible solution is that complex, intelligent life, just is not that common, requiring special planets, and special circumstances to direct the evolution of intelligent species.

Take Earth, complex animal life has... about 1 billion years left, being optimistic here, before the sun's output has increased too much.

4 billion years have passed, 1 billion to go, were 80% through the usable lifetime of our star (for this planet's orbit), and we don't have the capability to be self sufficient in space, or go to other stars. All the evolutionary innovations we have (limbs, fingers, eyes, ears, a brain, a neocortex, etc) have been around for at least 300 million years, only now have they given rise to a technology using species

If we nuke outselves into extinction, or pollute ourselves into extinction, Earth will likely never produce a spacefaring species...

And earth had a lot going for it.

We may only have a handful of planets give rise to intelligent species per galaxy.

So, lets treat the Earth as special, lets assume its a very special planet, perhaps no other planet in the galaxy had the "right stuff" that Earth has.

Maybe we should act like we are perhaps the galaxy's only hope at a space faring civilization, and that if we fail, there will be no one to take out place... a vast expanse devoid of life... no aliens will visit earth and learn our story, it would be lost forever.

Or...

Maybe there is an alien probe out in the Kuiper belt right now, keeping tabs on us...

So lets make a good impression and treat our planet and each other well.

[Nuke]

im starting to like the slow colonization approach. with appropriate energy sources (fusion, hell even fission would work, all be it in a more limited fashion) one could make many otherwise hostile objects in the solar system habitable through artificial means (were not talking terraforming). tunneling several meters underground, you can get out of the radiation. if there is water you can breath and drink and grow food. sometimes in objects with low enough gravity to require a centrifuge. but as resources on each object dwindle and population grows, you send seed colonies to the next body. eventually you have colonies all over the kuiper belt, the oort cloud, stretching out about a light year. assuming all stars have a similar cloud, its only going to be about a 2 light year jump to get from our cloud to alpha centauri's cloud. i think using this method you could colonize a huge chunk of the galaxy in as little as a few tens of thousands of years.

if that happens for aliens, you are not going to see warp drives blinking everywhere. nuclear-electric is enough to make the small jumps required, possibly with nuclear pulse propulsion in the interstellar gaps. they could be living out in the oort cloud and just haven't colonized their way over here yet.

Edited April 20, 2014 by Nuke

[Simon Ross]

In honesty, you don't have to look much further then your nearest bit of vegetation for a pretty alien life form. Takes in CO2 and releases Oxygen as a by product.

It kinda debunks one of the main requirements straight away, you pretty much cannot have free oxygen in a standard atmosphere without a life form already producing it

[Chrisd857]

A really good Sci-Fi novel, Dragon's Egg, explores this hypothesis...very well done book

http://en.wikipedia.org/wiki/Dragon%27s_Egg

On an unrelated note, the whole fast-developing civilization aspect reminds me a lot of Blink of an Eye from Star Trek: Voyager.

[KerikBalm]

In honesty, you don't have to look much further then your nearest bit of vegetation for a pretty alien life form. Takes in CO2 and releases Oxygen as a by product.

It kinda debunks one of the main requirements straight away, you pretty much cannot have free oxygen in a standard atmosphere without a life form already producing it

Who was saying that molecular oxygen was one of the main requirements?

Its not even a requirement for animal life...

You do need the element oxygen though

[-Velocity-]

I agree with the idea that much of the "life" in the cosmos might not be "life" to us (or, some of us, that is). For example, intelligent machines. I would consider them a form of life, but many people wouldn't due to their anthropocentric biases towards chemical/organic life. But intelligent machines could easily be the most common form of life in the universe, since they would be able quickly and intelligently redesign themselves to adapt to a huge variety of environments. We, on the other hand, are naturally evolved organics, and unless we take an active role in our own evolution, we adapt much more slowly and inefficiently, and would never really be able to adapt to life in, say, deep space, for example.

[Sillychris]

The biggest problem with silicon based life is that silicon has a much higher affinity for oxygen than carbon does. This means that when oxygen is around, you get silicates (silicon dioxide) formed preferentially and an inhibition of complex molecule formation.

It doesn't strictly negate the possibility of silicon based life, but you will have to find a way around the oxygen problem.

[Palladium Corp]

The problem with the requirement for an earth-life atmosphere for life is that the Earth did not have an earth-like atmosphere when life first arose. In fact, there was practically no free oxygen at all on earth because it is so reactive.

[pxi]

Did anyone here read Richard Dawkins The Selfish Gene?

It's been years since I read it, but if I recall correctly, he speculated that fundamentally, beyond any physical mechanism, life may be defined by the propagation of patterns of information. Therefore by this view, we, and all life on earth are machines, designed to replicate our DNA.

What I found intriguing, was his speculation that essentially culture was another parallel form of life that is transmitted from person to person, and is subject to mutation and natural selection in much the same way as DNA does.

See here: Selfish Gene, Chapter 11.

[Alchemist]

The biggest problem with silicon based life is that silicon has a much higher affinity for oxygen than carbon does. This means that when oxygen is around, you get silicates (silicon dioxide) formed preferentially and an inhibition of complex molecule formation.

It doesn't strictly negate the possibility of silicon based life, but you will have to find a way around the oxygen problem.

You can't just replace C with Si, some other things will change. Si-based biochemistry would probably include much more heteroatoms, for example cyclic structures could be based on silicon nitride, but instead of long -C-C-C-C- chains could be polysiloxanes -Si-O-Si-O-Si-O-Si- (with the other 2 bonds occupied with another structures).

Si-Si bond in nowhere as strong as C-C, but than only means you'll have to add something else. We already have plenty of O and N in our biochemistry, but silicon-based would probably include even more.