I am currently creating a Spacefaring Race that regularly travels between planetary systems in order to harvest resources, but due to the fact that the conditions required for them to Breed are fairly specific, they must regularly return to their homeworld in order to reproduce, in much the same way Salmon on Earth do. This has been a fairly constant theme throughout their species' evolutionary history, and since they are driven by instinct to return to their birthplace on their own planet they have developed remarkable navigational skills that have served them well as they ventured out into space.
However, on their own planet, at least part of their success in accurately navigating complex long-distance migration paths came through their acute sense of smell (Again, much like Salmon). While I do have a means by which they can fairly accurately navigate in space (in addition to Extremely Advanced Spacial Awareness Skills and a natural penchant for gauging the distances/positions/speeds/sizes of Objects, they also have developed Spectroscopic Vision that allows them to use stars of particular compositions as Landmarks or Waypoints), I was wondering if there would be a way for them to incorporate Scent, or if this would have be limited specifically to their exploration of planets and moons.
If they could somehow sniff the vacuum of space without suffocating... Is there even anything to smell, if there's no air to carry it? What would space even smell like? Could things leave a reliable scent-trail in a vacuum?
If not, is there another alternative that they might find similarly intuitive?