As described earlier in the analysis, the alien who eventually 'combines' with Bowman represents Melusina (also known as Melusine), the feminine aspect of Mercurius. From Jung's Alchemical Studies:
"[Melusina] was descended from the whale in whose belly the prophet Jonah beheld great mysteries. This derivation is very important: the birthplace of Melusina is the womb of the mysteries, obviously what we today would call the unconscious...Melusina can be interpreted as a spirit, or at any rate as some kind of psychic phenomenon...Melusina is clearly an anima figure. She appears as a variant of the mercurial serpent, which was sometimes represented in the form of a snake-woman by way of expressing the monstrous, double nature of Mercurius. The redemption of this monstrosity was depicted as the assumption and coronation of the Virgin Mary...
"The anima belongs to those borderline phenomena which chiefly occur in special psychic situations. They are characterized by the more or less sudden collapse of a form or style of life which till then seemed the indispensable foundation of the individual's whole career...One is confronted with a hopeless and impenetrable darkness, an abysmal void that is now suddenly filled with an alluring vision, the palpably real presence of a strange yet helpful being."[a]
a. Jung, C.G. The Collected Works of C.G. Jung, Vol. 13. Princeton University Press, 1967. pp. 143, 144, 177.
