Millions of years ago, the Earth was so cold that vast tracts of its surface lay under a thick sheet of ice, giving the planet the look of an enormous snow globe. This narrative draws on observations from geologists who have found glacial deposits even near the equator, areas where such icy formations are least expected. If ice extended so far from the poles, it raises the question of whether the planet was entirely frozen.
Yet, the certainty of a completely frozen world has always been debated. Some scientists argue that there could have been zones only partially covered by ice, or pockets of open sea where oxygen could seep in and life could take root.
Recent research published in Nature Communications appears to support this possibility, proposing that an open ice oasis may have existed in the tundra far north of what was previously imagined.
Key evidence comes from the discovery of a thin layer of black shale that might have persisted beneath sea water during the Marinoan glaciation, which began roughly 650 million years ago. Found in southern China, this shale acts like a fossil record of ocean conditions from that era.
New version of the world as a ‘snowball’ Nature Communications
By analyzing iron and nitrogen levels, scientists can determine whether oxygen was entering the ocean and whether life forms were producing nitrogen.
Researchers describe evidence of ice-free conditions in mid-northern paleoenvironments, explained by Huyue Song, a participant in the study, to AFP. He notes that ice-free zones have previously been identified mainly in equatorial regions.
Instead of a narrow belt of ice-free territory along the equator, there may have been much broader expanses that remained ice-free, according to Song, a professor at the University of Geosciences in Wuhan, China.
frozen landscape the wall is here
The work extends prior studies from Australia to Brazil, which suggest life could endure in small refugia even when the rest of the planet was frozen.
Incubators for life’s comeback
These refugia may have fostered a rapid rebound in the biosphere once the ice retreated. The research argues that life could reestablish itself quickly at the end of the ice ages.
Song and colleagues believe these findings will help scientists better understand Earth’s climate system and the long arc of how life has evolved and persisted through deep time. While ice ages are ancient history, the implications could inform how modern climate change unfolds and how resilient life can be in the face of extreme conditions.
Such findings offer information about how life endures extreme weather events and may become increasingly relevant as contemporary climate pressures intensify. This line of inquiry deepens the understanding of planetary habitability and the resilience of biospheres under stress.
Reference article: Nature Communications, 2023, Fig. 3
…