A new study supported in part by the NASA Astrobiology Program is helping astrobiologists understand how aerobic eukaryotes may have survived in Earth’s oceans during the planet’s most severe ice ages. These global events, often referred to ‘Snowball Earth’ periods, occurred between 720 to 635 million years ago and took place at an important time in eukaryotic evolution. The survival of eukaryotic aerobes in the ocean during Snowball Earth events would have required the persistence of oxygenated habitats, yet little is known about how such habitats would have been maintained while the oceans were capped with ice.

By studying iron formations within glacial deposits, the authors of the new study provide insight into the redox state of the Earth’s oceans while they were trapped beneath the global ice sheet. The team believes that oxic meltwater underneath the glaciers mixed with anoxic waters, ultimately fueling microbial communities that supported aerobic ecosystems in localized areas. This ‘meltwater oxygen pump’ could have been essential for the survival (and continued evolution) of aerobic eukaryotes during Snowball Earth periods.

The study, “Subglacial meltwater supported aerobic marine habitats during Snowball Earth,” was published in the Proceedings of the National Academy of Science of the United States of America (PNAS), and features in an article from the New York Times that is available here. The work was supported in part through the NASA Astrobiology Institute (NAI) element of the NASA Astrobiology Program.