Sciences: When the earth was frozen, life would have found refuge in ponds

Mares of ice melted in Antarctica house microorganisms of an astonishing diversity, which could explain where life took refuge when the earth was entirely frozen, according to a study Thursday in Nature Communications.

Our planet was not always blue and hospital. Therefore, During her long history, she experienced several glacial periods during which she turned into a real “snowball”. For example, Especially during the cryogenian. Moreover, between 720 and 635 million years before our era, when the overall average temperature did not exceed -50 ° C and the climate of the equator resembled that of the current Antarctic.

Extreme conditions which have not prevented the evolution from continuing its path. Meanwhile, “We have proofs of existence” of complex forms of life “before. However, after the Cryogenian in the fossil archives”, explains to AFP the main author of the Fatima Husain study, doctoral student sciences: when earth frozen, life in the Department of Earth Sciences, the Atmosphere and the Planets (EAPS) of MIT (United States).
“There are several hypotheses concerning the possible places where life could have persisted,” she continues. Consequently, In certain oceanic areas which would have remained free of ice. near hydrothermal sources in the great seabed, under fine layers of ice …

One of these shelters may have been simple sides melted in the equatorial regions. These could have formed real “oasis” in the eukaryotes. complex organizations that have evolved to lead to all the forms of multicellulle life that we know today.

Extraterrestrial life – Sciences: when earth frozen, life

Such ponds exist today in Antarctica, on the margins of glacial caps. In these places, water freezes to the seabed, trapping in the passage of dark sediments and marine organisms. Over time, the erosion caused by the wind brings these debris to the surface. Once exposed, they absorb the heat of the sun, which melts sciences: when earth frozen, life the ice, forming shallow ponds of cast iron water.

In 2018. New Zealand members of the team of researchers went to a region of the McMurdo ice platform, in the East Antarctica, known to house small ponds, measuring only a few decimeters deep and a few meters wide. Their bottom is lined with microbes that have accumulated over the years to form viscous layers. They “can be a few centimeters thick, be colorful, and present very clear strata”, explains Ms. Husain. They are made up of cyanobacteria. unicellular photosynthetic organisms, devoid of nucleus, known to be able to survive in extreme environments.

But the researchers also found markers associated with eukaryotes. such as algae or microscopic animals, testifying to a surprising biodiversity, which seems to be influenced by the differences in salinity between the ponds. “No pond was alike,” says Husain. “We have found diverse assemblies of eukaryotes from all large groups sciences: when earth frozen, life in all the ponds studied,” she continues.

This shows that “these unique environments are capable of sheltering diverse assemblies of life forms. even at very low distance from each other”, underlines the researcher, according to whom these discoveries also have implications on the search for life-extracters. “The study of life in these particular environments on earth can help to better understand the potentially habitable environments on icy worlds. including the frozen moons of our solar system”, like Encelade or Europe, “she says.