They can control the orbit of planet and that means zero because most time of the year mars isn't close to Earth
https://www.youtube.com/watch?v=z8aBZZnv6y8
even being close to Earth, the distance is light years away and they can just use another route. Nothing complicated to undertand.
I really wonder how people think the space is to think mars is a barrier.
You know when a road is blocked and you take a shortcut? Space is the same wbut with more possibilities