I can't tell if this is real or not. First, I think you know that Mars isn't the farthest planet from the sun in our solar system. Second, everything we know about our current solar system is irrelevant. We don't yet know exactly what the Traveler has done to our system. Maybe when he terraformed the planets, he also changed all of the orbits so that they can all be inhabitable. We are also far into our future. Third, there have been some theories that we are actually in a Vex matrix. Maybe we are in a computer simulation and we are not actually on the planets. Maybe the Vex don't actually know what our solar system is like. These theories are based on some hints in Grimoire cards.