Have you considered the possibility of Mars being terra formed in the future? When you do the Vault of Glass, the two time gates take you through TIME. The left is referred to as "Mars" and the right is "Venus." But they are really the same room in the present, but the left is the past (note the Predecessor Vex) and the right is the future (Descendant Vex.) Venus in the past is barren. Venus in the future is overgrown.