Somebody is going to have to patrol out to Mars due to SpaceX’s colony. If they build a fueling Station in Mars Orbit, then you can put sensors out past Jupiter to catch inbound objects. Plus, once SpaceX gets a station in Orbit, people are going to the asteroid belts to get shiny rocks.
We are not that far away from having permanent bases off planet. There will be a SpaceX flag on Mars in 5 years, there might be graves around it but it will be there.
Nobody “needs” to patrol anything.
Musk said he did not want any earth interference in his mars government, and I don’t blame him