Alien question for all you science people

[Super Dude]

I don't know why I was just thinking about this, but do scientists have any conception/imagination about what a non-carbon-based life form would be like/look like? Just wondering.

[7StringedBeast]

They already found non carbon based life forms on earth.  Somewhere in the Ocean (I forget where) they found Arsenic based life forms.

https://www.wired.com/wiredscience/2010/12/nasa-finds-arsenic-life-form/

[Super Dude]

Whoa, that shit's crazy.

[Sigz]

That's still a carbon based lifeform, it's just able to substitute phosphorous with arsenic.

My knowledge on the matter is quite incomplete, so take this for what it's worth. However from what I do know carbon is important because it has the ability to bond into chains, something rather unique to carbon, and at this point a trait that may be necessary for life. I think current theory says that a silicon based lifeform may be possible, as silicon has similar properties to carbon (though is much rarer).

[Orbert]

The science fiction people put a lot of stock in silicon-based life because of its similar properties.  Immediately below carbon in the periodic table, it also has four valence electrons and therefore will tend to combine with other elements in many of the same ways as carbon, although that's a gross oversimplification.  The problem is that it's also a much heavier atom, and as Sigz says, much rarer as well.

As for what it would look like, that's a completely open-ended question.  What does carbon-based life look like?  The variety of life forms on this planet alone is virtually infinite, so predicting what non-carbon-based life would look like seems pretty futile.

[yorost]

Now hold on you two, silicon is far more abundant than carbon on our planet.

https://hyperphysics.phy-astr.gsu.edu/hbase/tables/elabund.html

On the crust Silicon makes up more than a quarter of all matter(overall a little lower since the core is almost entirely iron), but carbon is only .03% of matter on all of Earth

[Sigz]

Wow, totally didn't know that, TIL.

[rumborak]

FYI, the scientist who pushed for the arsenic life form has been heavily criticized for her methods, and the jury is still out on whether this wasn't just a case of sloppy science.

rumborak

[bosk1]

Didn't know that.  The only thing I ever heard about the arsenic life forms was:  It's a miracle they lived; it's a blessing no one died.

[Orbert]

Hmm, actually that makes a lot of sense.  All that sand on all the beaches all over the world... silica.  Oh well.

[Scheavo]

Isn't silicon less available than carbon? That's different than saying there's more carbon atoms than silicon on Earth, because it needs to be "available" for a chemical reaction (just like Hydrogen is extremely common, but it's not easily available for energy use).

[millahh]

Silicon has some similar properties to carbon,  but it lacks an equivalent to the sp3 hybrid configuration of carbon, which is what makes the long chains energetically/geometrically favorable.  Silicon can make chains when alternated with oxygen atoms (I.e. glass) , and it is possible to branching or side-groups, but I've never seen anything suggesting that it would be a good candidate for a self assembly.

[Chino]

The properties of the planet (mainly the size of it) would have a much greater effect on an alien life form than a non-carbon atmospher would.

[Scheavo]

By the way, I say we go look for life on Titan. Out of all our possibilities, I think Titan would tell us the most, even if we find nothing.

[XJDenton]

Titan and Enceladus.

[Scheavo]

I guess Titan get's all the news. I guess I remember hearing about Enceladus, but guess I missed the hype about it. I still personally think Titan would be more interesting, because it presents something really different. Enceladus could tell us a lot, but I don't think it would be as radically new as Titan would be, if you get what I mean.

But I guess I'm sorta expecting to find bacterial in the solar system, so for me its of what kind, not if.

[TempusVox]

My hope is we plunge the icy depths of Europa sometime in my lifetime. I'm not talking about the EJSM, but something more ambitious like what the Russians wanted to do. Can you imagine seeing footage from a submersible cruising through the water beneath the ice? That would be amazing.

[Chino]

My hope is we plunge the icy depths of Europa sometime in my lifetime. I'm not talking about the EJSM, but something more ambitious like what the Russians wanted to do. Can you imagine seeing footage from a submersible cruising through the water beneath the ice? That would be amazing.

All of this. Europa > Titan

[kári]

Pretty much all astronomers agree that if there is extraterrestial life, it will most likely also be carbon based.
https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements

Look at the table on the right "Ten most common elements in the Milky Way Galaxy estimated spectroscopically[1]". By extrapolation, this is also valid for the rest of the universe today. As you can see, there's just a LOT of carbon. That's one reason.
Another reason is carbon can bond to 4 other atoms, a property not many other elements posses. The next element in the list that has 4 valence electrons is Silicon but it's by good approximation 10x rarer than carbon. Which makes a lot harder than 10 times for two Silicon atoms to bond than for two carbon atoms.

Both of those arguments translate itself into the fact that if you look at the molecules with more than 2 atoms that we have detected so far, pretty much all of them contain carbon (the only one containing silicon and not carbon is SiH4 from a quick glance at the article below).
Take a look at this: https://en.wikipedia.org/wiki/List_of_molecules_in_interstellar_space and tell me that extra-terrestial life, if it exists, will not be carbon-based.

[hefdaddy42]

My hope is we plunge the icy depths of Europa sometime in my lifetime. I'm not talking about the EJSM, but something more ambitious like what the Russians wanted to do. Can you imagine seeing footage from a submersible cruising through the water beneath the ice? That would be amazing.

ALL THESE WORLDS
ARE YOURS EXCEPT
EUROPA
ATTEMPT NO
LANDING THERE
USE THEM TOGETHER
USE THEM IN PEACE

[Orbert]

Ha ha, nice!  I totally forgot about that.  Europa is off limits.

[Scheavo]

My hope is we plunge the icy depths of Europa sometime in my lifetime. I'm not talking about the EJSM, but something more ambitious like what the Russians wanted to do. Can you imagine seeing footage from a submersible cruising through the water beneath the ice? That would be amazing.

All of this. Europa > Titan

Can we just agree that we should go to all of em? I mean, really, it's like lining up a bunch of hot women and asking, "which ONE do you want to have sex with?" All of em, please.

[XJDenton]

I guess Titan get's all the news. I guess I remember hearing about Enceladus, but guess I missed the hype about it. I still personally think Titan would be more interesting, because it presents something really different. Enceladus could tell us a lot, but I don't think it would be as radically new as Titan would be, if you get what I mean.

But I guess I'm sorta expecting to find bacterial in the solar system, so for me its of what kind, not if.

Turns out I actually meant Europa. Bit of a fail on my part.

[Sigz]

Not sure about what's most likely to have life, but Europa seems like the obvious first stop just because of the distances involved.

[Scheavo]

Not sure about what's most likely to have life, but Europa seems like the obvious first stop just because of the distances involved.

Well, getting to Saturn wouldn't really cost more, and I for one don't think waiting a few years is all that big of a difference, considering the task.

[Chino]

Not sure about what's most likely to have life, but Europa seems like the obvious first stop just because of the distances involved.

Well, getting to Saturn wouldn't really cost more, and I for one don't think waiting a few years is all that big of a difference, considering the task.

Europa is all all liquid water (beneath the surface ice) with thermal activity.... Sounds like a very logical choice to me.

[Scheavo]

Not sure about what's most likely to have life, but Europa seems like the obvious first stop just because of the distances involved.

Well, getting to Saturn wouldn't really cost more, and I for one don't think waiting a few years is all that big of a difference, considering the task.

Europa is all all liquid water (beneath the surface ice) with thermal activity.... Sounds like a very logical choice to me.

I know.

Titan has water, as well as lakes made from gasoline, a dense atmosphere and a climate system. Studies of the atmosphere indicate the potential for life due to depletion of hydrogen and acetylene (https://www.spacedaily.com/reports/Have_We_Discovered_Evidence_For_Life_On_Titan_999.html). It's not proof of life, but I'd say that's about as much evidence as we could ever want to look for life. It's just as logical as Europa.

This is only like, if I had to choose the two, by the way.

[Chino]

I honestly think if we look in the right places, we will find it on Mars.

[hefdaddy42]

I honestly think if we look in the right places, we will find it on Mars.

https://www.youtube.com/watch?v=nlvYKl1fjBI

[TempusVox]

My hope is we plunge the icy depths of Europa sometime in my lifetime. I'm not talking about the EJSM, but something more ambitious like what the Russians wanted to do. Can you imagine seeing footage from a submersible cruising through the water beneath the ice? That would be amazing.

ALL THESE WORLDS
ARE YOURS EXCEPT
EUROPA
ATTEMPT NO
LANDING THERE
USE THEM TOGETHER
USE THEM IN PEACE

So, should colonists finally arrive there to live, someone could actually be a "European Europan". 

[Scheavo]

I honestly think if we look in the right places, we will find it on Mars.

Probably. Someone found bacterial life in basically Mars life conditions on earth. It's just in lava tubes, something rather hard to get to with small remote probes.

[Dr. DTVT]

Silicon has some similar properties to carbon,  but it lacks an equivalent to the sp3 hybrid configuration of carbon, which is what makes the long chains energetically/geometrically favorable.  Silicon can make chains when alternated with oxygen atoms (I.e. glass) , and it is possible to branching or side-groups, but I've never seen anything suggesting that it would be a good candidate for a self assembly.

Beat me to it.  Guess that's what I get for only coming over to P/R on occasion.  I don't see any element that can form the complex frameworks that carbon does quite regularly.  There are plenty of other reasons silicon and other elements won't work, most of them having to do with bond strength/angle/ability to bond with another atom of itself.

[Orbert]

High school was a long time ago for me, but I remember a bit about covalent bonds, and how Carbon could have a triple covalent bond with another Carbon atom, and it's the only element that can do that.  My chem teacher also explained why, but I don't remember.

But yeah, Carbon was all over the place, bonding and hooking up with just about any other element, in ways that other elements could only dream of.  The sleezebag whore of the chemistry world, as it were.

[Dr. DTVT]

It's real thing is carbons ability to bond with other carbon atoms.  You can't make long strings of nitrogen, oxygen, silicon, or phosphorus without some other bridging atom.

There are some metal-metal quadruple bonds, but they are rare and man made compounds.  I thought I heard about a metal-metal quintuple bond, but I don't follow the inorganic literature so don't quote me on that one.

[Chino]

I honestly think if we look in the right places, we will find it on Mars.

Probably. Someone found bacterial life in basically Mars life conditions on earth. It's just in lava tubes, something rather hard to get to with small remote probes.

Mars has those annual Methane bursts. Whether its like or geological is a different story though.... It'd be sick if it was cave dwelling creatures.