Where do we start our Search for E.T. Life?
There are a lot of stars, planets and moons in the Galaxy! Despite the chance of over-looking
something important, we must try to limit our search to planets and moons most likely to support
life. These four fundamental characteristics have been identified:
Perhaps the most important of these? Liquid Water
Exobiologists consider the search for E.T. life to be equivalent to a search for
Liquid Water. What is so special about water?
A) Water serves as a medium in which nutrients and waste can be dissolved and transported, and
as a chemical reactant itself.
B) Water exists as a liquid over a large and favorable Temperature Range. At high pressures, it can
stay as a liquid (deep hot oceans). Consider other possible exobiological liquids:
Liquid Freeze Boil Range
NH3 -78 C -33 C 45
CH4 -182 -164 18
C2H6 -183 -89 94
Other liquids have a small range, and exist as a liquid only at very low Temperatures.
But, chemical reactions favor warmer temperatures: Evolution is 100x slower in liquid NH3,
not to mention the chilly temperatures of liquid CH4 and C2H6.