On the presence of liquid in Earth's inner core

Seismological studies indicate that the inner core of Earth is anisotropic for compressional waves (P waves), and has low shear wave (S wave) velocity, and high seismic attenuation. Using an effective medium theory for composite materials, we show that the presence of a volume fraction of 3 to 10% liquid in the form of oblate spheroidal inclusions aligned in the equatorial plane between iron crystals is sufficient to explain the aforementioned seismic phenomena. Variation of S-wave velocity between the polar axis and equatorial plane is more sensitive to the addition of liquid than that of P waves. The liquid could arise from the presence of dendrites or a mixture of elements other than iron that exist in liquid form under inner-core conditions.