They were an engine drilled into the surface of a comet. When the ice was gone, they would grind up the rock and use it for reaction mass. When the dust was gone they would coast, an engine and a life-bubble headed past the point where the solar wind gave way to the void.
No one had ever been this far out before. The people they were running from had long since stopped chasing: it would have been a stern chase of years and a spectacular waste of resources.
They weren't coming back. They couldn't even if they wanted to.