Does life exist elsewhere in the universe?
21 Sep 2012, 10:20 am
AspieRogue wrote:
Jono wrote:
AspieRogue wrote:
Nope. There are chemical reason for the impossibility of silicon based life. Notably the length of silicon hydrogen is large enough that silanes decompose spontaneously. Silicon also is not capable of forming stable double bonds which play a large role in metabolism. The only stable macromolecules of silicon are silicone polymers which are monotonous and useless for any kind of biochemistry.
That only applies if we are talking about polymers formed by direct bonds between silicon atoms as an analogue to organic compounds. You haven't considered the possibility of a silicon-based biochemistry based on silicone type compounds, i.e. polymers of large molecules made up of chains of alternating silicon and oxygen atoms, which are much more stable and diverse like organic compounds. It is still actually possible and conceivable that there could be silicon-based with a biochemistry based on reactions with silicone compounds.
Yes I have. Silicone polymers are entirely synthetic and involve silicon-oxygen-hydrocarbon molecular parts. In nature, Silicon combines with oxygen but silicates do not form polymers nor any sort of precursor molecules the way carbon does. No prebiotic complex molecules involving silicones have ever been found in nature. That in itself says a lot.
First of all, just to point out that silicones do not necessarily have to have the hydrocarbon parts, those are called organosilicon compounds, but that's besides the point. Anyway, humans cannot ultimately do anything that nature can't because synthetic chemistry is still based on the same laws of physics that naturally occurring chemistry is based on. The fact that we haven't found naturally occurring silicones only means that will not occur in those environments. However, also note that other planets do not have to have environments that are identical to those on Earth, in fact many of the extraterrestrial environments that we know about are already radically different from Earth's environment.
The only real objection that I can think of is that, in the interstellar medium, complex silicon-based molecules are rare compared to the varieties of carbon-based ones, with only 8 such compounds being identified by astrophysicists as opposed to 84 different carbon-based compounds being identified. However, even this may mean that silicon-based life might be rare compared to carbon-based life but it doesn't completely rule out the possibility. Also silicone type compounds are not the only possible way a silicon-based biochemistry can come about. See, for example:
http://plutao.dpi.inpe.br/col/dpi.inpe.br/plutao%4080/2010/06.29.20.11.27/doc/SearchForLife120.html
21 Sep 2012, 11:40 am
Jono wrote:
AspieRogue wrote:
Jono wrote:
AspieRogue wrote:
Nope. There are chemical reason for the impossibility of silicon based life. Notably the length of silicon hydrogen is large enough that silanes decompose spontaneously. Silicon also is not capable of forming stable double bonds which play a large role in metabolism. The only stable macromolecules of silicon are silicone polymers which are monotonous and useless for any kind of biochemistry.
That only applies if we are talking about polymers formed by direct bonds between silicon atoms as an analogue to organic compounds. You haven't considered the possibility of a silicon-based biochemistry based on silicone type compounds, i.e. polymers of large molecules made up of chains of alternating silicon and oxygen atoms, which are much more stable and diverse like organic compounds. It is still actually possible and conceivable that there could be silicon-based with a biochemistry based on reactions with silicone compounds.
Yes I have. Silicone polymers are entirely synthetic and involve silicon-oxygen-hydrocarbon molecular parts. In nature, Silicon combines with oxygen but silicates do not form polymers nor any sort of precursor molecules the way carbon does. No prebiotic complex molecules involving silicones have ever been found in nature. That in itself says a lot.
First of all, just to point out that silicones do not necessarily have to have the hydrocarbon parts, those are called organosilicon compounds, but that's besides the point. Anyway, humans cannot ultimately do anything that nature can't because synthetic chemistry is still based on the same laws of physics that naturally occurring chemistry is based on. The fact that we haven't found naturally occurring silicones only means that will not occur in those environments. However, also note that other planets do not have to have environments that are identical to those on Earth, in fact many of the extraterrestrial environments that we know about are already radically different from Earth's environment.
The only real objection that I can think of is that, in the interstellar medium, complex silicon-based molecules are rare compared to the varieties of carbon-based ones, with only 8 such compounds being identified by astrophysicists as opposed to 84 different carbon-based compounds being identified. However, even this may mean that silicon-based life might be rare compared to carbon-based life but it doesn't completely rule out the possibility. Also silicone type compounds are not the only possible way a silicon-based biochemistry can come about. See, for example:
http://plutao.dpi.inpe.br/col/dpi.inpe.br/plutao%4080/2010/06.29.20.11.27/doc/SearchForLife120.html
The chemical diversity of silicon in terms of bonds with nonmetals is far more limited than that of Carbon. Earlier I suggested boron based life which is far more plausible because both oxyboranes and nitroboranes are highly stable and boron, unlike silicon, can form stable boron-boron bonds which silicon cannot. In nature, silicon behaves very much like a metal and so it would not be able to compete with carbon in the presence of nitrogen and oxygen. That's why there's no silicon based life on planet Earth despite the abundance of silicon: Because the silicon in the crust was oxidized and then mineralized. Outside of the laboratory, silicon behaves chemically very much like a metal and I have yet to see evidence where the kind of chemical conditions that are used to create silicone polymers could occur in nature. In fact, silicon is 10 times more abundant in the Universe than Carbon is and here on Earth the total mass of silicon is much larger than the total mass of all carbon. And yet there are no silicon-based lifeforms hear on Earth, despite the fact that certain microbes can metabolize silicon even though they're made of carbon. I do not think that is coincidental. Monotonous carbon polymers that are used to make plastics do not occur naturally despite the existence of many types of organic carbon-based polymers.
