Scientists record coldest ocean temperature ever in Earth's history—and wonder how life survived | National Geographic

Scientists have recorded the coldest ocean temperature ever in Earth's history, estimated to be 5°F (minus 15°C), during the Snowball Earth period about 700 million years ago. The study, published in Nature Communications, found that the oceans were 22°F (12°C) colder than today's coldest ocean temperatures and had salinity more than four times higher, allowing them to avoid freezing. This discovery raises questions about how life could have survived such extreme conditions, with theories suggesting adaptations to limited oxygen and light, survival at hydrothermal vents, or in meltwater ponds on the ice.