Around 700 million years ago, the world is thought to have experienced its most severe ice age -- a period evocatively described by scientists as Snowball Earth.
원문출처 : https://www.cnn.com/2019/12/03/world/life-survive-ice-age-snowball-earth-scn/index.html
원문출처 : https://www.cnn.com/2019/12/03/world/life-survive-ice-age-snowball-earth-scn/index.html