Trapped neon in ureilites - a new component

Noble gases in five recently found ureilites were analyzed by conventional noble gas mass spectrometry and, in one case, by closed-system combustion mass spectrometry of an acid-resistant residue. From analyses of the Hajmah ureilite we derive a composition for trapped neon of 20Ne/22Ne=10.4±0.3, 21Ne/22Ne=0.027±0.003. Since this differs from all other known components of trapped neon, we propose the name Ne-U for this composition the occurrence of which may not be restricted to ureilites alone. Its composition is compatible both with being fractionated solar Ne and being a mixture of solar Ne and Ne-E. The associated He has a ratio 3He/4He<5x10-4, within the range of other trapped He compositions. Closed-system combustion data demonstrate the presence of an easily combustible fraction with low 36Ar/132Xe ratio, in accordance with our earlier suggestion for the existence of a second gas component in addition to that residing in diamonds. Attempts to characterize this phase in the Nilpena ureilite which had been reported to be diamond-free met with little success, because it turned out that diamonds are present. In the case of ALPHA 78019, more work is required