Quote:
Originally Posted by CraigS
Ok .. a summary of some info comparing Carbon ( C) vs Silicon (Si) biochemistry follows (from Wiki):
- Si has the same valency as C (ie: four), so it is theoretically large enough to carry biological information
- Si lacks the ability to form chemical bonds with diverse atoms .. (req'd for metabolism), when compared with carbon;
- has difficulty forming double, triple or covalent bonds, thus it lacks the diverse compound morphologies formed by Carbon (important for biochemistry);
- compounds of H and Si are highly reactive with water and long chains of these decompose;
- silicones (polymers of Si and O) are more stable than hydrocarbons in suphuric acid environments (quite common);
- complex long chain silicones are less stable than their C counterparts;
- silicon dioxide is a non-soluble solid at temps where water is liquid;
- Si based life breathing Oxygen would produce a solid by-product, thus respiratory organs would be filled with sand. This can be overcome at very high temperature or pressure environments .. (ie: not Mars surface);
- as at 1998, in the interstellar medium, 84 molecules are based on C, whilst only 8 are based on Si. Of those eight compounds, four also include C;
- the cosmic abundance of C to Si is about 10:1, (complex carbon compounds are thus more abundant to support C based foundation for life on planetary surfaces, than Si compounds);
- however, the abundance of Si to C on Earth is about 925:1 and yet, terrestrial life is C based. Thus it seems that C is more successful at forming life, in spite of its less comparative abundance, than Si;
- compounds formed by Si block the flow of heat, nonetheless biogenic silica is used by some life on Earth. Thus lifeforms comprising combinations of C and Si could achieve metabolism and digestion;
So, in terms of maximising the chance of detecting life on Mars' surface, from the above physical facts perspective, it would seem to make sense to constrain the probe/laboratory design around detecting Carbon based organic life … over the Si based life alternative.
Cheers |
Yes....all true. However, silicon based lifeforms would fall under the category of "life as we don't know it". That's what I said originally...how would we test for it. Especially if our life paradigm is looking for carbon based life, or lifeforms that metabolise, etc, in a similar fashion to carbon based forms.
What if the silicon based lifeforms were all solid state and crystalline in nature, which would most likely be the case. How are we going to test for that?? Would you even recognise it as being alive??. You could walk right past it and not even notice. Given our present technology and scientific paradigm in this respect, detecting such lifeforms would be very difficult. For one, we're not looking for them, and we also don't have the equipment to distinguish a silicon crystalline lifeform from a lump of rock.
They may or may not exist, granted, but we'll never know unless we go looking for them...or meet up with one at some stage. We're biased because we are carbon based and it's much easier to detect. But that doesn't mean we should ultimately limit ourselves to carbon based life. To do so would be wholly unimaginative and scientifically narrow minded. Even if we never find any, at least we'd have explored the possibilities.
Just had a funny thought....imagine having a deep conversation with what appeared to be a large lump of rock crystal
Wait a minute, there's some people who already do this!!!!!