In the 1960s, the noble gases neon and xenon were discovered to have unusual isotopic ratios in primitive meteorites; their origin and the type of matter that contained them was a mystery. These discoveries were made by vaporizing a bulk sample of a meteorite within a mass spectrometer, in order to count the relative abundance of the isotopes of the very small amount of noble gases trapped as inclusions. During the 1970s similar experiments discovered more components of trapped xenon isotopes. Competing speculations about the origins of the xenon isotopic components were advanced, all within the existing paradigm that the variations were created by processes within an initially homogeneous solar gas cloud.