Now we enter the fifth decade of the Mantegna deck, the 'Firmaments of the Universe' or 'The Heavenly Spheres'. They represent the order of the heavens, following the Ptolemaic view of his geocentric model. In this model, all 'planets' - including sun and moon - moved around the earth which was the fixed center of the universe. Closest to the earth was the moon which starts this last sequence of cards.
Here we see the moon goddess driving her chariot across the skies, holding the crescent of the moon in her hand. She is Selene, the Greek goddess, said to drive a silver chariot pulled by long-maned horses or winged dragons.
The Moon has its traditional place in Tarot, even though trump 18 strays away from the depiction of the goddess. The Mantegna cards instead pay full credit to the Renaissance's love of Greek (and Roman) mythology.