Carbon- and water-based life forms

Although life forms could be conceived using any of the chemicals in the Periodic Table, the ability of carbon to string together with itself and other molecules to form polymers is unique and makes it a compelling choice for the primary chemical 

Astrochemistry from astronomy to astrobiology. Andrew M. Shaw 2006 John Wiley Sons, Ltd 

Water is the solvent for life on Earth and it has a number of important properties that which might set the standard for other life-supporting solvents  

Water is liquid over a wide temperature range of 0-100°C, although the boiling point may be increased under pressure and the melting point may be decreased by the presence of dissolved salts. 

The density of ice is less than that of water so that ice floats. Having a frozen ice cap protects life below the ice, whereas a solid phase that sinks means that solid forming near the cold surface will sink, leaving new liquid to freeze and eventually freezing throughout any body of liquid. 

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