![]() ![]() Furthermore, measurements of oxygen isotopes in meteorites show that the solar system as a whole is not homogeneous in terms of isotopic ratios. On this scale, uranium – the abundance of which in the Sun is only 10 -12 that of hydrogen – is an exceedingly rare element. The terrestrial planets, including the Earth, are relatively depleted in the potentially gaseous or volatile elements (hydrogen, helium, carbon and neon) and are dominated by elements of low and even atomic number (oxygen, magnesium, silicon and iron). In fact, spectroscopic measurements show that the abundances of elements in stars vary and that there is no single applicable 'cosmic abundance' pattern.Ĭloser to home, there are major differences in abundances of the elements in the various planets that orbit our hydrogen-helium dominated Sun. Can we track through time the way uranium has been recycled through the exosphere, crust and mantle of the Earth?įor many years, since the 1930s, a large number of scientists have been occupied with determining the abundances of the elements and their isotopes in the objects comprising the solar system, and with accounting for the abundance patterns observed.What effects has the comparatively trivial uranium content of the Earth had on the evolution of the planet and, conversely, are there feedbacks controlling the geochemical cycle of uranium that vary secularly (i.e.Where did the uranium now in the Earth come from?.From a geochemical point of view, some of the major questions are: Their work stems from Klaproth's discovery in 1789 of the heaviest naturally occurring element, Becquerel's demonstration in 1896 that uranium salts are radioactive, Boltwood's conclusion in 1905 that lead as well as helium is a decay product of uranium, and Rutherford's suggestion in 1906 of the geological time-keeping potential of radioactivity. Geologists and geochemists have been studying the abundance, distribution and chronometric potential of the isotopes of uranium for more than a century. Radioactive decay contributes about half of the Earth’s heat flux.Uranium later became enriched in the continental crust.More recent research suggests some uranium is formed in the merger of neutron stars. The Earth's uranium had been thought to be produced in one or more supernovae over 6 billion years ago.Uranium is used to generate about 10% of our electricity worldwide, yet this fact pales into insignificance when we consider the role uranium has played in the evolution of the Earth.
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