A new analysis of ancient glass beads embedded in rocks from the inside of Australiasuggests that The Earth had dry land and fresh water about 4 billion years ago. This challenges previous scientific theory that the planet was completely covered in ocean during that time.
Chemical clues contained in the crystals revealed that the hot, molten rocks from which they originated entered into contact with fresh water during crystal formationaccording to a study published in the journal Nature Geoscience.
“By examining the age and oxygen isotopes in small crystals of the mineral zircon, we find unusually light isotopic signatures dating back to four billion years ago“, said Hamed Gamaleldienlead author of the study and research associate at the School of Earth and Planetary Sciences at Curtin University in Australia, in a press release.
And he added: “These light oxygen isotopes are usually the result of the alteration of rocks by hot, fresh water. several kilometers below the Earth’s surface”.
Gamaleldien explained that the evidence for the presence of fresh water could only be explained by the existence of dry land, where water would accumulate and seep into the continental crust. “We have two important things here. We have discovered the earliest evidence of fresh water and representative evidence of land over the sea”he explained.
The investigation also revealed that the Earth’s water cyclein which water moves between land, oceans and the atmosphere through evaporation and precipitation, it was already in operation at that moment.
This finding, according to the authors, means thatThe recipe for the origins of life existed about 500 million years earlier than estimated and less than 600 million after the formation of the Earth. The oldest widely accepted evidence of life (and fresh water) comes from stromatolites, fossilized microbes that formed mounds in hot springs 3.5 billion years ago, Gamaleldien explained.
The co-author of the study Hugo Olierooksenior researcher at the Curtin School of Earth and Planetary Sciences, highlighted: “This discovery not only sheds light on the early history of the Earth, but also suggests that land masses and fresh water set the stage for for life to flourish in a relatively short period of time: less than 600 million years after the planet formed”.
He Hadean Aeonfrom 4.5 to 4 billion years ago, is the oldest chapter in Earth’s history and a geological moment that is little understood because geologists simply don’t have rocks that old to study.
Nevertheless, zircons, the tiny mineral grains studied, are particularly hard and can be cemented into younger rocks. The studio zircons were found in 3.1 billion-year-old orange sandstone Of the information Jack Hillsan outcrop of eroded rock in Western Australia.
These zircons incorporate some uranium into their structure, allowing scientists to determine their age by measuring the radioactive decay of uranium ions. The oldest material of terrestrial origin was a zircon found in Jack Hills dating back to 4.4 billion years ago. “Zircon is a unique mineral. It is very resistant and does not alter over time”Gamaleldien explained.
To reach your findings, The researchers extracted, mounted and polished 2,500 grains of zircon before dating 1,400 of them and measuring different oxygen isotopes within the zircons. Salt water contains heavier oxygen isotopes, which are resistant to evaporation, while rainwater contains lighter isotopes.
The team performed 10,000 simulations of zircon composition using a computer model and discovered that just a little fresh water could explain the light isotopic signature of their zircons.
