Silicon identified as ‘missing element’ in Earth’s core
Scientists from Tohoku University in Japan have claimed that Silicon (Si) is the ‘missing element’ in the Earth’s core. This discovery could help us to better understand how our world formed. According to them silicon likely makes up a significant proportion of Earth’s core after its major constituents iron and nickel. It was missing element in the deep interiors of our planet that has eluded us for decades.
- It was found that silicon is a major element and constitutes about 5% of the Earth’s inner core by weight. It could be dissolved into the iron-nickel alloys.
- For the study, scientists recreated the high temperatures and pressures found in the deep interior of the Earth’s core. They recreated alloys of iron and nickel and mixed them with silicon.
- They then subjected these alloys to the immense pressures and temperatures that exist in the inner core.
- Scientists discovered that this mixture matched what was seen in the Earth’s interior with seismic data.
Note: The innermost part of Earth i.e. core is thought to be a solid ball with a radius of about 1,200 kilometres. It is far too deep to investigate directly, so scientists study this region’s make-up using seismic wave. Earth’s core is mainly composed of iron (makes up about 85% of its weight) and nickel (accounts for about 10% of the core).
- The light elements in the core could constrain the conditions of accretion, subsequent magma ocean, and core formation stages of the Earth. There are several studies for sound velocity measurements of the iron-light elements alloys.
- However, the measurements are not enough to constrain the light element abundance in the core tightly at present due to inter-laboratory inconsistencies using different methods which are originated from the difficulties to make such measurements under the extreme conditions.
- We measured the sound velocity of iron alloy compounds at high pressure and temperature relevant to the Earth’s core using double-sided laser heating of a DAC combined with inelastic X-ray scattering at SPring-8.
- We measured the compressional velocity of hcp-Fe up to 166 GPa and 3000 K, and derived a clear temperature dependence of the Birch’s law for hcp-Fe.
- We measured the compressional velocity of Fe0.89Si0.11 alloy and Fe3C at high pressure and temperature, and we could not detect temperature dependency in Birch’s law in these compounds. Additionally, we measured the sound velocity of Fe3S, Fe0.83Ni0.09Si0.08 alloy, and FeH at high pressure.
- Combining our new data set which showed remarkable differences from previous data on the sound velocity, we present a model of the chemical structure of the inner core. The outer core composition was also estimated based on partitioning behaviors of these light elements between solid and liquid iron alloys under the core conditions.