I agree g-man. I think they would have to determine 'what' dark matter is made of and try to detect the particles somehow. This again would be hard as the 'background' noise would most certainly mask it. I would have thought that 'Voyager' and all those other probes would have had some sort of detection instruments for ANY particles etc they encountered along the way. Maybe not so much the earlier ones but the later models??

As one of the theories of propulsion was to use hydrogen scooped up by a ramjet of sorts, from memory? They would have had to see if it was there wouldnt they? or that 'something' was there at least.

cheers bullet