“We were confident that the rocks of the Champua region were even older than previously thought,” says Mazumder, 53 now an associate professor of applied geosciences at the German University of Technology in Oman.

They were right. In 2,018 they published a paper in the journal Scientific Reports on two zircon crystals they extracted from rocks taken from the Champua site. While the rocks were 3.4 billion years old, the crystals were much older, at an estimated 4 and 4.2 billion years old.