Let´s use the asteroids as a space ferries

This is the paradox, an asteroid would exterminate the humankind but at the same  time would allow the humankind  colonize the solar system and save their DNA in a safety heaven. So I will use the power of Zero Data (pure intuition) in this blog to formulate an idea that could works and is your duty to check it works,  using Big Data power.

Let´s use the asteroids as a space ferries in order to build small human colonies on them and generate a  itinerary travel between Earth and Mars.
For instance, the (6178) 1986 DA asteroid which is a 2.3 kilometre diameter M-type Mars-crosser and near-Earth asteroid, could be colonized and used as a permanent ferry between Earth and Mars.
An asteroid ferry will have the advantage of not needing fuel and just use the gravity force for locomotion