Washington: Life somehow survives in this season, called Snowball Earth, and a new study provides a deeper understanding of why. According to the study, life on our planet faced a severe test during the Cryogenian period, which lasted from 720 million to 635 million years ago, when the Earth’s runaway glaciation was twice frozen over the ice and looked like a snowy viper from space.
Seaweed fossils unearthed in black shale in central China’s Hubei Province indicate that marine habitats were more widespread at the time than previously known, scientists said Tuesday. The findings support the idea that there is more of a “Slushball Earth” where the first complex life forms – basic multicellular organisms – persisted even in mid-latitudes, previously thought to be frozen solid.
Fossils from the second of two periods in the Cryogenian period, when large ice sheets extended from the poles to the equator. This interval, called the Marinoan Ice Age, lasted from about 651 million to 635 million years.
“The key finding of this study is that open-water – ice-free – conditions existed in mid-latitude oceanic regions during the waning stage of the Marine Ice Age,” said China University of Geosciences geobiologist Huyue Song, lead author of the research published in the journal Nature Communications.
“Our study shows that, at least near the end of the Marinoan “Living Earth” events, habitable areas extended to the middle latitudes of the oceans, much larger than previously thought. Previous research argued that such habitable areas, at best, only existed in the tropics. explain where and how complex organisms such as multicellular algae survived,” added Song.
The findings show that the world’s oceans were not completely frozen and that habitable reservoirs existed where multicellular eukaryotic organisms — the domain of life that includes plants, animals, fungi and some mostly solitary organisms called protists — could survive, Song said.
Earth was formed about 4.5 billion years ago. The first single-celled organisms arose in the first billion years of the planet’s existence. Multicellular organisms came later, perhaps 2 billion years ago. But it was only during the Cryogenian that conditions returned to warmer temperatures, paving the way for the rapid expansion of diverse life forms about 540 million years ago.
Scientists are trying to better understand the impact of the “Living Earth”. They believe that a reduced amount of the sun’s heat reaches the planet’s surface, as solar radiation is emitted from the white ice piles.
“It is generally believed that atmospheric carbon dioxide levels plummeted just prior to these events, causing the polar ice caps to expand and thereby reflecting more of the sun’s rays into space and further expanding the polar ice caps. Inspired by Earth’s snowball conditions, Virginia Tech geobiologist and study co-author Shuhai Xiao said.
Algae and fossils of some other multicellular organisms have been identified in the black shale. This alga – a rudimentary plant – photosynthetic organism lived on the sea floor in a light marine environment lit by the sun. “In fossils, compressed organic carbon sheets are preserved,” said China University of Geosciences paleontologist and study co-author Qin.
Multicellular organisms including red algae, green algae and fungi emerged before the Cryogenian and “Snowball Earth” survived. The Cold Cryogenian was much worse than the most recent Ice Age that humans survived, ending about 10,000 years ago.
“During the most recent Ice Age, the ice coverage was much wider, and more importantly, the amount of ocean was frozen,” Xiao said.
“It’s fair to say that the ‘We Live on Earth’ event poses significant challenges to life on Earth,” Xiao added. It is possible that these events could have driven the Earth’s major extinctions, but apparently life, including complex eukaryotic organisms, survived, testifying to the resilience of the biosphere.