Confronting Friends and Family

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NASA has discovered a new life form, a bacteria called GFAJ-1 that is unlike anything currently living in planet Earth. It's capable of using arsenic to build its DNA, RNA, proteins, and cell membranes. This changes everything.

http://gizmodo.com/5704158/nasa-finds-new-life

Silicon life would probably be based on Silicones, polymers of alternating silicon and oxygen. While in general silicones are less stable than hydrocarbons, they would have an advantage in certain environments. In particular, in an atmosphere or environment where sulfuric acid was common, silicones would have greater resilience than carbon-based molecules.

Silicones do run into some troubles, however. Namely, silicon that gets exposed to oxygen often forms silicon dioxide. Since it would be the analog of carbon dioxide, there's reason to believe such life would exhale it as part of respiration - breathing out dust and sand. Silicon dioxide is a solid at most temperatures, and not water-soluble, so you'd have problems removing this waste from cells, recycling biological material, etc. Now, "life may find a way", and in the case of silicone-life it's possible the solution would be ammonia. See Ammonia as Biological Solvent for a discussion of how it might work.

So, the environments most friendly to Silicon-based life are rich in ammonia and sulfuric acid. Ammonia's boiling point is below water's freezing point, so the planet would either be very cold or have extreme pressure (because at higher pressures, the boiling point of ammonia is much higher) - say, 60 atmospheres. Ice Giants and places like Titan, moon of Saturn might be viable habitats for silicon-based life. In other words, any planet likely to be hospitable to silicon life isn't going to be nice for humans. Maybe, just maybe, you might be able to get around that by having a Cloud Planet scenario - a layered Gas Giant that has some breathable earth-atmosphere at the high altitudes and a high-pressure silicone-ammonia environment further down. The notion of shared environments is iffy, to say the least.Silicon life would probably be based on Silicones, polymers of alternating silicon and oxygen. While in general silicones are less stable than hydrocarbons, they would have an advantage in certain environments. In particular, in an atmosphere or environment where sulfuric acid was common, silicones would have greater resilience than carbon-based molecules.

Silicones do run into some troubles, however. Namely, silicon that gets exposed to oxygen often forms silicon dioxide. Since it would be the analog of carbon dioxide, there's reason to believe such life would exhale it as part of respiration - breathing out dust and sand. Silicon dioxide is a solid at most temperatures, and not water-soluble, so you'd have problems removing this waste from cells, recycling biological material, etc. Now, "life may find a way", and in the case of silicone-life it's possible the solution would be ammonia. See Ammonia as Biological Solvent for a discussion of how it might work.

So, the environments most friendly to Silicon-based life are rich in ammonia and sulfuric acid. Ammonia's boiling point is below water's freezing point, so the planet would either be very cold or have extreme pressure (because at higher pressures, the boiling point of ammonia is much higher) - say, 60 atmospheres. Ice Giants and places like Titan, moon of Saturn might be viable habitats for silicon-based life. In other words, any planet likely to be hospitable to silicon life isn't going to be nice for humans. Maybe, just maybe, you might be able to get around that by having a Cloud Planet scenario - a layered Gas Giant that has some breathable earth-atmosphere at the high altitudes and a high-pressure silicone-ammonia environment further down. The notion of shared environments is iffy, to say the least.

http://arcana.wikidot.com/silicon-based-life

Life does not need to limit itself to what you understand to be possible.