I have no specific knowledge to add, but regard dark matter as a disaster for the simple mind to understand.
We send a space craft to Pluto which arrives exactly on time, and the equations pay no heed to dark matter, yet this pervades the galaxy with its 80% of all matter. I think the simple mind can be excused for not getting quickly to grips with dark matter. I wish it could be shown to be a hoax.
Actually, it's not that hard to understand why it doesn't affect the probe much, if you understand the
Shell Theorem.
When a star system forms, normal matter forms an accretion disk BECAUSE it interacts with other normal matter and is braked. Dark matter doesn't get braked and doesn't accrete, because it just passes through normal matter.
I.e., it has no real reason to end up in the Sun or very near it, which is the mass that dominates the gravity equations from here to Pluto.
What it ends up being is roughly a blob of dark matter gas filling the whole galaxy.
Essentially in the Pluto travel equation you have somewhere between 99.8 and 99.9 of the mass being the Sun, and buggerall visible mass between it and say, Alpha Centauri. Whereas in the dark matter's case there's buggerall in or around the Sun, and the vast majority of it spread over the vast distances in all directions. It's spread out over all those massive spaces between the stars.
If you do the maths of what affects the gravity that affects the probe when it passes Pluto, all the dark matter that matters is in a sphere with the radius of Pluto's orbit. Cf the shell theorem. Well, there's not that much there. The local density in our solar system is a mere 0.3GeV/cc. By way of comparison that 0.3GeV is less than a third of a proton's mass. The vast majority will be outside the shell, so it doesn't really matter for gravity calculations.
Dark matter makes up by being spread over all those cubic lightyears inside the galaxy, but in any given point the density will be very very small.
And the other reason I mention that shell theorem is also that such galaxy sized blob will mostly affect our movement around the galactic centre. And assuming a more or less radial symmetry in its distribution (which isn't 100% true, but close enough for our purposes here), what matters is the mass contained in a sphere with the radius being the distance between us and the galactic centre.
Well, between us and Pluto that radius doesn't change much. Essentially Pluto just moves around the galactic centre together with the Sun, and the correction you'd need to make because of dark matter is really insignificant.
That's the short and skinny of it, basically.
