Could you find what a lunar crater is made of by shooting it?

Americans are famously fond of their guns. So it should come as no surprise that a team of NASA scientists has devised a way to "shoot" a modified type of sensor into the soil of an otherworldly body and determine what it is made out of. That is precisely what Sang Choi and Robert Moses from NASA's Langley Research Center did, though their bullets are miniaturized spectrometers rather than hollow metal casings.