Two interesting claims about dark matter this week, and on the face of it, completely contradictory, but in fact, not obviously so. Before saying one word more, let me repeat my mantra — something that all physicists know but relatively few non-scientists appreciate — most claims of a radical new result turn out to be largely or completely wrong. This is not because physicists are stupid but because doing science at the forefront of knowledge involves using novel techniques that might have unknown pitfalls, and also because a single small mistake can create a fake effect (as we saw most recently with the OPERA neutrino speed measurement.) And because nasty statistical accidents can play tricks on you.
Both claims that I’m about to describe use novel techniques, and their analyses have not been repeated by anyone else. At this point you should understand that both are tentative, and (based on the history of radical claims) the odds are against them. Both might be wrong. That said, both analyses look to me as though they’ve been reasonably well done, and if a mistake has been made, it will require someone far more expert in dark matter studies than I am to point it out.
So let me describe them in turn, to the best of my ability.