Displaying Dinosaurs at The Natural History Museum,London

Dinosaur reconstructions have been exhibited in public for over a hundred years. During that time, scientific and public understanding of these extinct animals has changed considerably. Changes in perception have influenced and been influenced by the three-dimensional reconstructions mounted in museums and galleries, and these in turn have been influenced by the availability and use of mounting materials and techniques. The dinosaur exhibition in The Natural History Museum (NHM) in London contains examples of original, altered, and new dinosaur reconstructions that are described here—two, Gallimimus and Massospondylus, in detail. The final form of any reconstructed dinosaur is often influenced by factors beyond the control of the conservation, preparation, and mounting workers involved.     

Mineralogy of the deep lower mantle in the presence of H2O

Understanding the mineralogy of the Earth''s interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM, 1800–2890 km in depth) and observed surprising mineralogical transformations in the presence of water. Ferropericlase, (Mg, Fe)O, which is the most abundant oxide mineral in Earth, reacts with H₂O to form a previously unknown (Mg, Fe)O₂H_x (x ≤ 1) phase. The (Mg, Fe)O₂H_x has a pyrite structure and it coexists with the dominant silicate phases, bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for (Mg_0.6Fe_0.4)O or beyond 2300 km for (Mg_0.7Fe_0.3)O. The (Mg, Fe)O₂H_x is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences (Mg²⁺, Fe³⁺ and H⁺). This important phase has a number of far-reaching implications including extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM and an internal source for modulating oxygen in the atmosphere.