Yes, because for the vast majority of minerals you can find in space, they are the same as those you can find (or synthesize) in spaceon Earth. A pyrite in space is a pyrite just like on Earth. A wollastonite in space is no different than a wollastonite on Earth.
Nearly all space minerals are present on Earth, but the converse is not at all true--plate tectonics, biological chemistry, and, very recently, human activity have produced a wealth of natural minerals seen nowhere else in the universe. A particular paper (poorly, imo) called this "mineral evolution", insofar as the mineral assemblage on Earth has diversified alongside biological life.
But to get back to your question, minerals are minerals no matter where they are formed, and hardness is an intrinsic material property--you can assign your shirt a place on the Mohs hardness scale, so you can assign any space-found material a place as well.
Because I forgot to mention it, the study of extraterrestrial geology (which is what the Apollo missions, all the Mars rovers, etc. were all about), is called Planetary Geology.