Demeter's Dust scent is based upon the typical fine bits of fabric or dirt from around the house that gives off that familiar and comfortable odor.
Our universe is a very dusty place. Dust usually shows its presence by blocking out light emitted from stars or nebula behind it, sometimes creating the illusion of a horse's head or a sombrero hat. But nobody really knows what a typical interstellar dust grain looks like. By studying how dust absorbs, emits, and reflects light, astronomers do know that interstellar dust is much different than the cell and lint based dust, found around a typical house.