Washington: The chemical make-up of meteorites has revealed that Earth's first crust was formed around 4.5 billion years ago.
The team measured the amount of the rare elements hafnium and lutetium in the mineral zircon in a meteorite that originated early in the solar system .
The heat and pressure in the Earth's interior mixes the chemical composition of its layers over billions of years, as denser rocks sink and less dense minerals rise towards the surface, a process known as differentiation.
Dr Yuri Amelin, from The Australian National University (ANU) Research School of Earth Sciences said that determining how and when the layers formed relies on knowing the composition of the original material that formed into the Earth, before differentiation.
The team accurately measured the ratio of the isotopes hafnium-176 and hafnium-177 in the meteorite, to give a starting point for the Earth's composition.
The team was then able to compare the results with the oldest rocks on Earth, and found that the chemical composition had already been altered, proving that a crust had already formed on the surface of the Earth around 4.5 billion years ago.
