In 2004, Japanese researchers at the Tokyo Institute of Technology found that high temperatures and pressures transform perovskite, the major mineral in Earth's mantle, into a new mineral called post-perovskite. Wentzcovitch's group contributed to this discovery by determining the structure of post-perovskite and by calculating the pressure and temperature conditions for its existence. They matched the conditions in the D'' layer.
In the current work, Wentzcovitch and colleagues demonstrate that the seismic properties of post-perovskite are much like the previously inexplicable properties found in the D'' layer. This is the most convincing evidence that post-perovskite is in the D'' layer and produces its strange seismic properties.
As the Earth cools, D'' becomes thicker. Its thickness is related to Earth's age and its aging processes. The discovery of post-perovskite in the D'' layer will also help us understand how the Earth has evolved, Wenttzcovitch said.
Proceedings of the National Academy of Sciences