The third planet from the earth (according to Ptolemy, that is) is Venus, here depicted as the goddess Venus, the Roman equivalent to the Greek Aphrodite. She enjoys the presence of three graces or possibly nymphs, while her son Cupid (also known as Amor or the Greek Eros) seems on the lookout for someone suitable to shoot an arrow at.
The card reminds of trump VI, The Lovers, mainly because of Amor's presence and Venus' habitus as the goddess of love. At a closer look, the Mantegna card lacks the duality of the Lovers trump, and that Cupid can be seen in both is not that meaningful. He just happens to be the symbol of love.
Further reading: Venus (Planets)