Two recent Nature articles offer possible progress in the quest to characterize dark matter. A Science Daily article quotes one of the authors, Tel Aviv University professor Rennan Barkana, to the effect that "the discovery offers the first direct proof that dark matter exists and that it is composed of low-mass particles."
Massive particles -- the weakly interacting variety being known as WIMPs and the strongly interacting version as SIMPs -- were long considered leading contenders to comprise dark matter. According to another article, WIMPs were pegged at being "about 100 times heavier than the proton." However, Barkana claims the new research puts the putative dark-matter particle at around "several" proton masses.