Computer simulations carried out by astronomers from the University of Groningen in collaboration with researchers from Germany, France and Sweden show that most of the (dark) matter beyond the Local Group of galaxies (which includes the Milky Way and the Andromeda galaxy) must be organized in an extended plane. Above and below this plane are large voids. The observed motions of nearby galaxies and the joint masses of the Milky Way and the Andromeda galaxy can only be properly explained with this "flat" mass distribution. The research, led by Ph.D. graduate Ewoud Wempe and Professor Amina Helmi, is published in Nature Astronomy.
It’s a stand-in for the lack of a better understanding currently. No one has detected dark matter in our solar system yet. It’s all just deviations from how huge amounts of matter should behave according to our formulas. Yes, Dark Matter is well established; because it’s convenient. But assuming some invisible existence to explain a lack of understanding is not science, that’s a religion.