Silicon: life beyond carbon

I visited Drumheller (Alberta, Canada) last month to see the fossil of dinosaurs at Royal Tyrell Museum. I am attaching some of the pictures. Most of the fossils were bones of different parts (of the dinosaurs), different species and different times. The bones that I saw were hard to believe that they are actually "bones". Mainly because we are used to see bones, which are white or yellowish or brownish at some extent. During that visit, I could not distinguish between an EGG and a ROCK kept side by side and I identified incorrectly (unbelievable ehh...?).
Believe me they (the bones) look like rocks.....hard solid rocks. My post starts now.

All of us know, life was not like this 200 millions years ago. What about the earth and life on earth before that? How was it? I do not know and no one is SURE about the answer. Basic elements that constitutes life are mainly Carbon, Oxygen, Hydrogen. (Of course many elements like nitrogen, calcium, phosphorous etc etc.. also are vital part of life on earth.. I think all of you will agree that the way these elements make bonds now, were different long back ago. Let us think of an alternative to this system of carbon-hydrogen based life.

I remember a line in Sriramcharitmanas by Tulsidaas, a well known and one of the most popular Hindu script, which reads... छिति जल पावक गगन समीरा, पंच रचित अति अधम शरीरा। it means our body is made up of SOIL, WATER, FIRE, SKY AND AIR. In simple words, it is said in Hindu mythology that our body is made up of soil. This is also interpreted as follows. after death our body is disposed and it goes into these above-said five components. Sometimes I wander whether it gives us some more information other than this. Is it possible to have a life with soil? There is no answer to this but there are hints from the mother nature to decode. Silicon and silicates are main constituent of soil and is in abundance in the nature on earth. Can we imagine a life system with silicon and its derivatives as the basic unit instead of carbon and its derivatives as we see it in present.

Keeping all these questions in mind I started searching what our scientific knowledge says about this. While searching, I saw a literature by Prof. E. REYNOLDS published in NATURE in year 1893. That paper is about looking at silicon analogues of carbon compound. Periodic table is of help for this kind of comparison. I am writing some of the matter from that paper because I think it is important. "..Carbon, whether combined with hydrogen, oxygen or nitrogen or with all three, is the great element of organic nature, while silicon, in union with oxygen and various metals, not only forms about one-third of the solid crust of the earth, but is unquestionably the most important element of inorganic nature....." he further writes.. "....The chief functions of carbon are those which are performed at comparatively low temperatures;hence carbon is essentially the element of the present epoch. on the other hand, the activities of silicon are most marked at very high temperatures;hence it is the element whose chief work in nature was performed in the distant past, when the temperature of this earth was far beyond that at which the carbon compounds of organic life could exist......."

Silicon's ability to make stable bonds with elements like nitrogen, hydrogen and oxygen indicates the possibility of a silicon based life possibly in other atmosphere other than oxygen (as it is now). Other possible atmosphere could be SULFUR. I suggest sulfur because it shows properties similar to oxygen due to their presence in the same group (group 16). Also sulfur is related to silicon in period third in the same way as oxygen is related to carbon in the second period. Apart from this silicon is capable of making long chains, multiple bonds and good bond strength with oxygen. Moreover, silicon also has an edge over carbon because of its solubility in aluminum. as it is said "silicon dissolves freely in aluminum". In a way Aluminum resembles nitrogen in directly forming bond with silicon at higher temperatures (here the comparison is between Si-Al and C-N). Si-Al dissolution and ability to stay together with ease and stability can be understood in terms of there coexistence in the crust of earth which has been named with them as SIAL (refer to the other part of crust called "Sima", consisting of silicates and magnesium).

Before saying final words for this post, I would like to make two points about the importance of silicon (and its derivatives) in our life. First, a complex derivative of silicon made up of Silicon, oxygen, hydrogen and carbon is used in many medical application including cosmetic implants. This material is called "polymerized siloxene" or more commonly known as "silicone". This material shows know side effects in our body if implanted in our body. Secondly, recent research shows the importance of SILICON in our nutrition for strong and healthy bones (Journal of Nutrition and health aging, Vol 11, page 99 (2007)).

Finally, Its time to think on the possibility of a life with silicon, aluminum and oxygen as basic building blocks instead of carbon, nitrogen and hydrogen. Life in terms of this silicon and group can be thought to be present in past on earth or may be the world outside our reach.  Science gave the answer about our evolution, courtesy Charles Darwin. But it reminds me of a statement by George Bernard Shaw.

Science never solves a problem without creating ten more.