Origin of freshwater on Earth

Fresh water is essential for life on Earth. But when did this crucial substance first appear on our blue planet?

New research led by geologists at Western Australia’s Curtin University provides evidence that fresh water emerged on Earth about 4 billion years ago – half a billion years earlier than previously thought.

The study is published in the journal Nature Geoscience.

of The  geologists examined ancient crystals from the Jack Hills in Western Australia, about 650km north of the state capital, Perth. The rocks in the formation are 4.4 billion years old, making them the oldest terrestrial material on Earth – our planet itself is 4.543 billion years old.

“We were able to date the origins of the hydrological cycle, which is the continuous process through which water moves around Earth and is crucial for sustaining ecosystems and supporting life on our planet,” says lead author Hamed Gamaleldien, from Curtin University.

It is believed that water first reached young Earth when the solar system first began forming 5 billion years ago in the form of ice from asteroids and meteorites which crashed into our planet as it formed.

“By examining the oxygen isotopes in crystals of the mineral zircon, we found unusually light isotopic signatures as far back as 4 billion years ago. Such light oxygen isotopes are typically the result of hot, fresh water altering rocks several kilometres below Earth’s surface,” Gamaleldien adds.

“Evidence of fresh water this deep inside Earth challenges the existing theory that Earth was completely covered by ocean 4 billion years ago.”

The research deepens and challenges our understanding of the origin of life on Earth.

“This discovery not only sheds light on Earth’s early history but also suggests landmasses and fresh water set the stage for life to flourish within a relatively short time frame – less than 600 million years after the planet formed,” says co-author Hugo Olierook, also from Curtin.

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