a core issue

At http://phys.org/print362144022.html … we learn that Earth's core contains more oxygen than previously allowed. Geologist Rick Ryerson and colleagues modeled geophysical and geochemical signatures they thought were involved in the formation of the Earth, accreting material that was more oxydised than the present day mantle material (on the basis that the material accreted would be similar to that of asteroids and planetesimals. The new model differs from the old model – but it is still a model. The research is published in September's PNAS (2015).