A quick refresher of the chemistry of water, CO2, and life:-

Water is an excelent solvent for polar (ionic) compounds like salt. CO2 is an excellent solvent for light organic compounds. Life consists of parcels (cells, globules) of complex chemistry, packaged in a lipid (fatty acid) membrane.

If water and liquid CO2 co-exist, they form small globules of one liquid in the other. At the interface, both polar and non-polar chemistry are possible.  Lipids naturally line up at the boundary and form sheets that seal in the globules. Perhaps this is the first, crucial step towards the origin of cellular life?

Maybe self-replicating chemicals already existed, but the packaging into cells was the vital step towards life as we know it. Perhaps conditions on the early Earth were cold enough for liquid CO2 to exist in some regions, and permit life to begin in this way? What a balance! Too cold and the water freezes. Too warm and the CO2 boils, and the greenhouse effect amplifies any change in insolation making the balance razor sharp.

If life required such a careful balance of temperatures to begin, then perhaps the habitable zone is much, much narrower than most people imagine?
 

      Created: May 2002
      Last modified: May 2002
      Authorised by:  Head, Earth Sciences

      Maintained by: Nick Hoffman
      Email: nhoffman@unimelb.edu.au