A SNOWBALL'S CHANCE

Aug 20, 2025

There was a time, between 635 and 720 million years ago, when the entire Snowball Earth was covered in snow and ice. It is called the Cryogenian Period, and Macroscopic organisms had not evolved yet. But single-celled organisms had evolved, and they persisted through the snowball period. MIT researchers went to the Antarctic to see how life survives there, under Snowball Earth conditions. They found microbes in sun-melted ponds on top of the ice. Every puddle contained eukaryotic life (that is to say, cells with a nucleus), and different ponds had different varieties depending on how salty they were. Dirty ice melted more easily and was more richly inhabited. Geologist Myron Cook explores how the intense glaciation of Snowball Earth flattened mountain ranges and exposed the geological mystery known as the Great Unconformity.”