i disagree strongly with the assertion that tellus is more common than gaia i've never heard or read of tellus used to mean earth except in some roman mythology stories while i often encounter gaia referring to the ecology or 'spirit' of earth in popular green and scientific ecologic term not that i agree that it is a scientific term a google search of gaia earth gave me million hits while tellus earth gives million most of the latter seem to refer to companies with that name