Methane based life?

[daniel l.]

In the recent short story i wrote on my website/fictional encyclopedia, I imagined that in the future, We would artificially create methane based life and then adapt the genetic profiles of Earth life to it, What would be the difference? I Imagine Titan dominated by tree's and grass all methane based. How would they look different from life on Earth? Also, Suppose we converted our own genome to it making Methane based humans, People who will be born live and die on Titan as if it were Earth, Will their skin still be the same color? Will their blood still be red. I am inquiring this as i am currently writing the next chapter of my storyline that takes place over a century after the previous one.

[KSK]

I think methane based biochemistry would be so completely different to terrestrial water based biochemistry that your Titans are unlikely to look much like humans at all, let alone have the same skin colours or red blood. For example, I found this  article which suggests that silicon based life (which would almost certainly look very different to carbon based life  ) might be possible on Titan. Quoting for convenience:

"The geologist Dirk Schulze-Makuch (Washington State University-USA) and the biologist Louis N. Irwin (University of Texas-USA) recently studied the possible pathways followed by life on other worlds, as alternatives to life-as-we-know-it on Earth (Schulze-Makuch and Irwin 2004). They questioned the possibility of a silicon-based life, a substitute to the carbon-based life known on our planet, a hypothesis previously suggested in the 1960s by V.A. Firsoff (Firsoff 1963, 1974). The best form offered by silicon for an exo-life would be a series of silicon hydrides, the silanes, consisting of Si-H and Si-Si single bonds. However the conditions required to make possible a silane-based life seem to be very restrictive: little or no water in liquid form, very low temperatures, little or no oxygen, suitable solvent such as methane, restricted abundance of carbon (Schulze-Makuch and Irwin 2004). According to these authors, the Saturnian moon Titan could meet these criteria, except the low abundance of carbon (but perhaps the cold and reducing conditions on Titan could lead silicon to have an advantage over carbon). However, no silane has been detected in Titan’s atmosphere, in spite of more than five years of closed observation of Titan"

On a different note, this discussion (started by a writer who was also wanting some detail about methane based life-forms) has some interesting posts on the problems of dealing with metabolic waste. Wikipedia also  has a (very) short article on alternative biochemistries which will hopefully have some useful links for you.

Sounds like an interesting story!

 

[Scotius]

If you have sufficiently advanced tech to rewrite molecular structure of a living being to such degree, you can pretty much make it look whatever you want.

[Green Baron]

All the elements life uses are based on efficiency of use and availability. They (C, O, Fe, Ca, H) all are abundant in space in what is built in earths metabolisms is very well/best suited for the job.

Reality: Methane as a "base" is difficult to imagine. Some bacteria can metabolize methane, either as "input" or as "output". Nevertheless they are carbon based lifeforms like every life on earth is. That is because carbon simply is the best fit element for life(tm) and it is abundant (in space). Other possible, but less reactive base elements could be silicon (like @KSK said) or sulphur, but

Fantasy: "organisms" on that base would most probably not walk around but rather sit on a mountain and watch the millennia pass (silicon) or nest near a volcanic vent and lament the cold season (sulphur) :-)

Red blood: that is because our muscles need oxygen as an energy supplier and oxygen is best bound by iron (haemoglobin). So red blood would belong to an organism that uses iron as a means to transport oxygen to the muscles. Other possibilities to bind oxygen are less effective or rarer (copper comes to mind- green blood of the vulcans :-)). The bind must not be too strong or too much energy is needed  to break it up. Also, the vertebrate's lungs are highly effective in exchanging O and CO2, other organs like tracheae of insects are less effective. Insects had their time in the carboniferous, when atmospheric oxygen level was much higher than today they grow to lengths of a meter. But then again, a high atmospheric oxygen level means that a single lighting strike can light a fire that lasts until everything has been oxygenised -> carboniferous coal.

So, what i want to say, converting something (or -one) to fit a selected environment is not easy if it shall look credible, since the whole organism must be taken into account. Study the "models" we have and had on earth and their supposed environments and lifestyle. It's hard to imagine something that is supposed to be totally different without using a lot of fantasy :-)

 

5 minutes ago, Scotius said:

If you have sufficiently advanced tech to rewrite molecular structure of a living being to such degree, you can pretty much make it look whatever you want.

In your fanatsy, yes. But if it shall be credible, then there are limitations depending on material, environment and processes :-)

Edited October 18, 2016 by Green Baron

[todofwar]

You couldn't rewrite earth based life, because on Titan all proteins and DNA are going to be frozen solid, and won't dissolve in methane. There have been a few theoretical studies done looking at possible methane based biochemistry, but implementing them would involve totally making up life from scratch. And such life forms could never be in the same room with humans unless one of them is in a space suit. We would freeze in methane, they would boil at room temperature. 

Silicon based life, by the way, wouldn't be slow I don't think. Silanes are incredibly reactive, violently so. And plenty of animals already use copper for oxygen transport (hemocyanin). Gives the blood a blue color. 

[KerikBalm]

 

14 hours ago, daniel l. said:

artificially create methane based life and then adapt the genetic profiles of Earth life to it, What would be the difference? I Imagine Titan dominated by tree's and grass all methane based.

Sorry, but no, just no.

Our genome encodes for proteins an amino acids that are water soluble. For the nucleic acids... if the methane based genetic molecule relies on complementary base pairing, then some of the sequence could be carried over to the new organism.

However, whenever the secondary structures formed by nucleic acids (very very often), the new molecule's properties would be so different as to require a completely new sequence. All the intron splicing signals and self splicing introns would be all fouled up. The exons/amino acid encoding parts would also have to be thrown out. What good is a sequence of amino acids to make an enzyme that catalyzesreactions for a biochemistry that you aren't using. What good is an amino acid sequence encoding a structural protein that relies on a completely different solved.

There would be no adaptation of genetic profiles, you'd basically have to throw it all out and start over again. I suppose you could make life that superficially resembles the shape of a human, but at the molecular level, it would be completely different. Lets not forget that bacteria are often pretty much the same shape but completely different genetically and chemically.

One wouldn't consider a rod shaped 7 micron long Archea to be comparable to a 7 micron long rod shaped Eubacteria. So whatever methane based life you refer to wouldn't be comparable/ an adapted genetic profile of a human

 

47 minutes ago, Green Baron said:

Reality: Methane as a "base" is difficult to imagine. Some bacteria can metabolize methane, either as "input" or as "output". Nevertheless they are carbon based lifeforms like every life on earth is. That is because carbon simply is the best fit element for life(tm) and it is abundant (in space). Other possible, but less reactive base elements could be silicon (like @KSK said) or sulphur, but

I think we're going to need to get a bit more specific in our terms here. We could call life water based, or we could call it carbon based. That depends on if you're talking about the complex biolmolecules, or the solvent that those biomolecules function in.

Methane indeed does have carbon. Methane based life would be carbon based. I am assuming he means Methane as the solvent instead of water.

This means you've taken a polar solvent and replace it with a non-polar solvent. This intoduces massive changes and may be a deal breaker right away.

One interesting thing it does is make the biomolecules "inside out" relative to water based life. Normally hydrophyillic domains make something soluble/are on the outside of a protein, and hydrophobic domains make something insoluble, often hydrophobic parts are associated with a membrane or are found at the interior of a large protein/complex.

Our lipid bilayers would be inside out. Normally they are composed of molecules with a hydrophylic head and hydrophobic tails, the tails face each other, and the heads face outwards (where the water is). In methane, this would be reveresed.

The polar properties of water are immensely important for many reactions in "water based" life. Water can also be changed into H3O+ and OH-.

With methane you'll just get CH3- or CH4. There won't really be any positively charged CH5 form as far as I know.

Its a very complex subject, so I can't say there aren't other ways it could work... just that it lacks many properties that are important to our form of life. Until we have examples of biology independent from ours, its a big question mark.

 

Quote

Red blood: that is because our muscles need oxygen as an energy supplier and oxygen is best bound by iron (haemoglobin). So red blood would belong to an organism that uses iron as a means to transport oxygen to the muscles. Other possibilities to bind oxygen are less effective or rarer (copper comes to mind- green blood of the vulcans :-)). :-)

Well, Titan won't have an O2 atmosphere. Even if you engineer life to go there... the fire hazard would be extreme. Water is unreactive with O2, Methane is not. Life based on a methane solvent is not going to be building up an oxidizing atmosphere.

Sure our carbon biomolecules are reactive with oxygen, but our solvent is not and that immensely moderates the risk of combustion.... which really only happens in dry conditions when that solvent is depleted. Its hard to imagine any reactive compound accumulating to large amounts in the titan atmosphere if we're still going to have lakes of methane, and all life on the world being methane solvent based. This basically means no breathing/ very low concentrations of the reactive compound and very slow movement and metabolism. One could still take in the atmosphere, in something similar to breathing, not for energy but for raw material/nutrients/building block like plants taking in CO2 (note plants also breath oxygen, obviously when its dark and they aren't producing any O2 or energy, they need an energy source).

 

Also, I find it facepalm worthy that you mention copper and "green vulcan blood" when Vulcans are complete fiction and do not exist.

We have plenty of examples of real animals with copper based blood.. and its generally described as blue, not green

https://en.wikipedia.org/wiki/Cephalopod#Circulatory_system

"Like most molluscs, cephalopods use hemocyanin, a copper-containing protein, rather than hemoglobin, to transport oxygen. As a result, their blood is colorless when deoxygenated and turns blue when exposed to air."

https://en.wikipedia.org/wiki/Horseshoe_crab#Blood

"Unlike vertebrates, horseshoe crabs do not have hemoglobin in their blood, but instead use hemocyanin to carry oxygen. Because of the copper present in hemocyanin, their blood is blue." (Note: horseshoe crabs are not crabs/crustaceans, and are more closely related to spiders than crabs)

https://en.wikipedia.org/wiki/Malacostraca#Internal_anatomy

"The typical respiratory pigment malacostracans is haemocyanin."

https://en.wikipedia.org/wiki/Hemocyanin

"Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form."

So, its already doubtful that they'd have blood at all (since respiring with a reactive compound in the atmosphere seems doubtful), but there's no reason for it to be red.... in fact its unlikely to be red even if there was O2 in the atmosphere:

"It has been noted that species using hemocyanin for oxygen transportation include crustaceans living in cold environments with low oxygen pressure. Under these circumstances hemoglobin oxygen transportation is less efficient than hemocyanin oxygen transportation."

Titan is cold. Due to a methane based solvent, you wouldn't want to accumulate O2 to high concentrations, the partial pressure of O2 should be low. Hemocyanin would work better than Hemoglobin in cold low O2 conditions. If we ignore the methane solvent thing (since neither of these would work in methane and not water), then it makes more sense for the blood to be blue.

[Green Baron]

Yes, you are right with the distinction of solvent and base. I didn't want to go that deep, just encourage OP to do further research on the subject. And thanks for the hint that CH4-diluted life wouldn't build up an O2-atmosphere.

See, one must allways have a broader picture to judge the credibility and a single change can pull a rat's tail of reengineering behind ...

:-)

Edit: @KerikBalm: You thougt i thought vulcans do exist ? Got you :-)

 

Edited October 18, 2016 by Green Baron

[KerikBalm]

no i didn't think that you thought they were real.

I'm just face palming that you chose fiction over reality for an example... particularly as the fiction has the wrong color (green, when it should be blue)