Our paper provides insights into a number of key areas of science which are currently the subject of active research. These include the early history and evolution of the Earth, its continents and oceans. In addition, it has relevance to the development of the Earth-Moon system and to the early evolution of the solar system—perhaps providing a unique opportunity to find evidence of short-lived nuclides that have long since become extinct. Furthermore, our conclusion that liquid water was present on the surface of the Earth much earlier than was previously thought has implications for the evolution of life.

We discovered a very ancient crystal of zircon (ZrSiO2 – zirconium silicate) in sedimentary rocks from Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton, Western Australia. This general region has long been known to contain the oldest material on Earth, with the discovery in the 1980s, at nearby Mt. Narryer, of crystals greater than 4,100 million years old. Our identification of the first crystal that is over 4,300 million years old—with a small portion as old as 4,404 million years—extends the age of the oldest terrestrial material to within ~150 million years of the formation of the Earth itself. Chemical data obtained from this crystal support the view that it formed within crust of continental type, thus implying that the Earth had at least a partially stabilized surface at this early time. This was not previously considered possible, since the consensus was that continued meteorite bombardment had destroyed any early crust that may have formed during this period. Evidence from oxygen isotopes supports the view that the oldest part of this crystal grew in an environment where liquid water interacted with this pre-existing continental crust to produce a new rock with a composition similar to granite. It is within this granitic rock that the ancient zircon crystal grew. The presence of liquid water implies that the surface temperatures on the Earth were much cooler than previously thought possible. This has significant implication for the early evolution of life on Earth, since all the pre-requisites were in place 4.4 billion years ago.