To understand how life emerged, scientists investigate the chemistry of carbon and water. In the case of water, they track the various forms, or isotopes, of its constituent hydrogen and oxygen atoms over the history of the universe, like a giant treasure hunt. Researchers from the CNRS, Paris-Saclay University, the French Alternative Energies and Atomic Energy Commission (CEA), and the University of Pau and the Pays de l’Adour (UPPA),1