Life may have survived far north of equator during ‘Snowball Earth’ | Science.
More than 600 million years ago, the planet was frozen from pole to pole, covered in half-kilometer-thick ice sheets that darkened every ocean.
How sea life clung on during Snowball Earth, as this inhospitable period is known, has long been a mystery.
A new study bolsters the idea that the global glaciation wasn’t all encompassing.
Geochemical evidence from ancient rocks suggests zones of open ocean may have been present north of the Tropic of Cancer, a region that was previously considered too cold to host life during this period.
“There’s a habitable zone,” says Shuhai Xiao, a geobiologist at the Virginia Polytechnic Institute and State Universityand co-author of the new work.
And it’s “perhaps wider than previously thought.”
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Other scientists aren’t yet convinced, however.
Foreign Far north of equator during snowball Earth science more than 600 million Years ago the planet was frozen from Pole to pole covered in half kilometer Thick ice sheets that darkened every Ocean Hal see life clung on during Snowball Earth as this inhospitable Period is known has long been a mystery A new study bolsters the idea that the Global glaciation wasn't All-encompassing geochemical evidence From ancient rocks suggests zones of Open ocean may have been present north Of the Tropic of Cancer a region that Was previously considered too cold to Host life during this period there's a Habitable zone says shuhai Xiao a Geobiologist at the Virginia Polytechnic Institute and State University and Co-author of the new work and it's Perhaps wider than previously thought to Stay up to date with latest top stories Make sure to subscribe to this YouTube Channel by clicking the button above This video other scientists aren't yet Convinced however climate simulations Have trouble creating even an ice-free Equator during snowball Earth periods The possibility that there was uncovered Ocean outside the tropics makes this Thing really difficult to swallow says Paul Hoffman a geologist at Harvard University who pioneered the snowball
Earth hypothesis climate models since The 1960s have shown how planetary deep Freezes can arise from a simple feedback Loop when temperatures drop Earth's ice Caps expand reflecting sunlight and Creating further cooling if the ice Manages to creep to roughly 30 degrees To 40 degrees latitude about where North Africa and the continental United States Are today the global climate enters a Runaway freezing cycle and Glaciers end Up covering the entire planet within a Few hundred years the geological record Indicates Earth has experienced at least Two such periods the most recent one is Known as the marinan Ice Age between 654 Million and 635 million years ago life Was limited to the oceans and large Creatures had yet to evolve but fossils Show that microscopic eukaryotes such as Algae lived before and after the episode Such organisms require sunlight and Open Water Xiao says you have to Envision Some sort of Refuge where these algae Cans survive previous work has shown That storm-driven currents may have been Openly circulating in Shallow Seas During the era although much of the Evidence remains ambiguous to study Conditions during this period Xiao and His colleagues examined a thin layer of Dark Shale found in shinanjia National Forest in South China that dates to the Meriden the researchers believe the
Shale originated from mineral-rich Ocean Mud that was laid down at mid-latitudes Perhaps between 30 degrees and 40 Degrees north Xiao and his colleagues Found the Shale was not only chock full Of various algal fossils but also Nitrogen compounds a thick ice sheet Would have cut the oceans off from the Atmosphere preventing oxygen from Entering their Waters but the nitrogen Compounds were found at levels similar To those in modern day oceans suggesting Oxygenated Waters where nitrogen and Oxygen were able to to freely interact The results indicate that the area where The Shale came from might not have been Capped with ice and was instead in a Boat where photosynthetic organisms Could Thrive the team reports today in Nature Communications if true it would Require climate modelers to tweak their Simulations and find ways to sustain an Open ocean over a long period of time Xiao says the results jive with multiple Lines of evidence from other studies Which indicate Clement conditions at Similar latitudes during the Ice Age Says Carol deller a geologist at Utah State University who wasn't involved in The work but Hoffman still believes it's Likelier that the fossils were from Microscopic algae that hit out in tiny Shallow pools of fresh water atop Glaciers today such pools appear in
Polar ice sheets and provide a refuge For cold adapted microbes all modern Algae are descended from freshwater Species Hoffman says suggesting that Those in the Seas were wiped out during Snowball Earth periods and had to Re-evolve afterwards turn to the ocean I Don't see the survival as being a Problem he adds nor does this paper Solve it it's also possible that all the Researchers are at least a little right There could have been a span in time Where even the equator froze over and Living creatures were forced into the Glacial pools but this interval might Not have endured for the entirety of the Marinen geologists know the dark Shale Lair came from the marinen but precisely When it Formed within the ice age is Unclear perhaps the rocks are a witness To the era's waning days a time when ice Sheets had already begun to retreat Deller says Xiao and his colleagues Agree with this Prospect we can't get Too used to any one model duller says we Need to be really open-minded because I Think we're going to find a lot of new Data will come out in the future Foreign