Ykhjuy

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?

Most likely not

To simplify smell, a creature is taking in atoms or molecules into a sensor, and those atoms or molecules stimulate the sensor.

Searching the web it seems it's generally accepted that there are approximately 100,000 - 1,000,000 atoms per cubic meter in Space. Contrast this with Earth's atmosphere at sea level, which has about 300,000,000,000,000,000,000 atoms per cubic meter (3*10^22).

Which means for every 1 atom in space you'll find 60 quadrillion atoms here on Earth. Your animals' senses of smell would have to be extraordinarily more powerful than any Earth creature's.

Smelling is almost the exact same as tasting with your tongue and they are very closely linked. It happens because particles react with certain cells, and those cells send a signal telling you what you are tasting/smelling.

Because it's space, there's almost no particles to interact with. You also can't create a lower-pressure area in your body to attract those particles into your nose.

The solution, if you want it, would be to have large sail-like pieces around your body that use their surface area to get enough particles to interact and give you an idea of your surroundings. You would have to know the particular (average) composition of particles of different solar systems and solar winds to make sense of them. I'm not saying it's impossible, I'm not saying it's possible, but it's not going to be a very easy or aestetically pleasing thing I think.