User blog comment:Spark321939/Are aliens good or will we be advanced enough?/@comment-1217267-20130429203217/@comment-160529-20130430221556

I only thought of this because of recent discussions concerning the possibility of a "shadow biosphere" the theory that there is a biosphere with a completely different chemical makeup on earth that we have yet to notice.

and although the theory is interesting, I am not entirely sure I believe. . . but I think it is very possible.