We can detect dark matter via its mass, that's why we know it exists. We can see it speeding up galactic rotations and acting to gravitationally lens more dista

We can detect dark matter via its mass, that's why we know it exists. We can see it speeding up galactic rotations and acting to gravitationally lens more distant galaxies and so forth. But we have yet to detect it on the small scale, especially at the individual particle level. Keep in mind that one of the key differences between dark matter and atomic matter within a galaxy, for example, is that dark matter has a nearly uniform density over very large volumes (many light years across) whereas atomic matter has enormous density variations, with huge expanses of near vacuum punctuated by ultra dense stars, planets, neutron stars, etc. Within our own Solar System the amount of dark matter inside a spherical volume that would extend out to Neptune's orbit is only as much as a comparatively small asteroid. As you scale out to larger and larger scales the fact that the density of dark matter is relentless causes the mass enclosed inside a volume to start to match (and ultimately exceed at the largest scales) the mass of stars, nebulae, planets, etc.