I still don't think it's good logic. There is no mechanism explaining why dark matter exists. So not seeing it in this case doesn't shake that theory because it gives no explanation in the first place. MOND does give some explanation so this becomes problematic. But what about a possible new 'dark force' being a possible explanation? Maybe this 'dark force' only radiates under certain circumstances.
I seem to have to qualify my statements with this but I am not attacking the idea of dark matter (nor am I defending MOND) I am just questioning the logic of this one point.
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I think it could be confusing what i mean by saying there is no mechanism explaining why dark matter exists. I just mean specifically why. It is a theory that postulates the existence of something but does not give a mechanism to how it gets there. This is not my field of research though so I could be terribly wrong about that.
There are indeed many reasonable dark matter candidates: sterile neutrinos, lightest supersymmetric partner, axions... These are particles which are theoretically motivated, but by their nature would be difficult to detect because they don't interact electromagnetically. If we exclude the existence of such particles it is more difficult to construct a coherent theory.
Dark matter is exciting in part because it intersects particle physics with cosmology, and has the potential to solve problems in both (e.g. rotation curves and neutrino masses). It's appealing in part because it's parsimonious.
I seem to have to qualify my statements with this but I am not attacking the idea of dark matter (nor am I defending MOND) I am just questioning the logic of this one point.
----Edit------ I think it could be confusing what i mean by saying there is no mechanism explaining why dark matter exists. I just mean specifically why. It is a theory that postulates the existence of something but does not give a mechanism to how it gets there. This is not my field of research though so I could be terribly wrong about that.