Another application is in radiochemistry, where this may refer to isotopic ratios or isotopic abundances. Isotope abundances and spin rates confirm this evolutionary difference between the two stars. Magmas are composed of melts and minerals in variable abundances. Species evenness quantifies how equal the abundances of the species are. Different studies generally find varying values for elemental abundances. There are two main methods of determining metal abundances in nebulae. The relative abundances depend on a single parameter, the ratio of photons to baryons. This is comparable to the crustal abundances of lead, cobalt, and niobium. Oozes are also useful in determining the historical abundances of siliceous organisms. Platinum exists in higher abundances on the Moon and in meteorites. Properties such as trace element abundances are analyzed systematically to locate anomalies. As a predictive theory, it yields accurate estimates of the observed abundances of the elements. The abundances of the noble gases in the universe decrease as their atomic numbers increase. It is responsible for the galactic abundances of elements from carbon to iron. Comparable abundances are found in taiga forests.