Carbon-depleted outer core revealed by sound velocity measurements of liquid iron-carbon alloy.

The relative abundance of light elements in the Earth's core has long been controversial. Recently, the presence of carbon in the core has been emphasized, because the density and sound velocities of the inner core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements.

Spin crossover and iron-rich silicate melt in the Earth's deep mantle.

A melt has greater volume than a silicate solid of the same composition. But this difference diminishes at high pressure, and the possibility that a melt sufficiently enriched in the heavy element iron might then become more dense than solids at the pressures in the interior of the Earth (and other terrestrial bodies) has long been a source of considerable speculation. The occurrence of such dense silicate melts in the Earth's lowermost mantle would carry important consequences for its physical and chemical evolution and could provide a unifying model for explaining a variety of observed features in the core-mantle boundary region.

The structure of iron in Earth's inner core.

Earth's solid inner core is mainly composed of iron (Fe). Because the relevant ultrahigh pressure and temperature conditions are difficult to produce experimentally, the preferred crystal structure of Fe at the inner core remains uncertain. Static compression experiments showed that the hexagonal close-packed (hcp) structure of Fe is stable up to 377 gigapascals and 5700 kelvin, corresponding to inner core conditions.

The advanced ion-milling method for preparation of thin film using ion slicer: application to a sample recovered from diamond-anvil cell.

The advanced argon ion-milling technique using a new instrument called ion slicer was newly developed for preparation of thin foil. Compared to the conventional ion-milling methods, this technique facilitates very wide area to be homogeneously thinned by rocking the ion beam source with low angle and the specimen during milling. Here we applied this technique to a sample recovered from a laser-heated diamond-anvil cell (DAC).