New light has been shed on our understanding of Earth’s early crust thanks to a new study in Nature Geoscience by NAI-funded researchers at the University of Wisconsin.

During the Hadean eon, between Earth’s formation and 4 billion years ago, the Earth differentiated into a core, mantle and crust. The planet was also resurfaced by bombardment of planetesimals and asteroids, as well as some form of plate tectonics. As a result, few rocks of Hadean age remain. Every scrap of material older than 4 billion years is therefore of great interest.

The oldest preserved crust was previously thought to have formed around 3.8 billion years ago, 600 million years after the Earth–Moon system formed, but over the past few decades older remnants of crust have been identified.

In the Jack Hills of Western Australia, a sandstone contains abundant zircon grains older than 4.0 billion years and analysis of more than 100,000 grains has yielded two that are older than 4.35 billion years. These grains are thought to be derived from continental crust, some of which could be more than 4.37 billion years old.

The age of the oldest Jack Hills zircons — Earth’s oldest minerals — is contentious. In this new study, atomic-scale mapping of the distribution of radiogenic isotopes within a Jack Hills zircon confirms that the oldest known continental crust formed just after the Earth–Moon system.