Ancient rocks indicate life may have originated in icy waters

New Scientist : When life first emerged on Earth some 3.5 billion years ago, the oceans may have been icy cold, according to a new study. Previous research on some of the oldest exposed rocks on Earth, South Africa’s Barberton greenstone belt, had indicated that ocean waters at that time could have been as warm as 85 °C. That conclusion was based on the balance of oxygen isotopes in the rocks. However, those rocks could also have formed in cold water and then gotten exposed to heat from hydrothermal vents, according to Maarten de Wit of South Africa’s Nelson Mandela Metropolitan University and Harald Furnes of Norway’s University of Bergen. The researchers argue that a colder ocean environment is indicated by the presence of the mineral gypsum and the fact that the rocks formed at a latitude of 20° to 40°. The scientists also say that key organic compounds important to the origin of life are more stable at lower temperatures and could become more concentrated in ice.