Nature: Scientists find that ancient crystals offer the first trace of fresh water

The study reveals evidence of fresh water could only be explained by the presence of dry land, where water would accumulate and seep into the continental crust.

A new examination of ancient crystal grains trapped in rock from the Australian outback reveals Earth had dry land and fresh water around 4 billion years ago, when scientists previously believed the world was fully covered with ocean water.

Chemical evidence found in the crystals suggested that the hot, molten rocks from which they formed came into contact with fresh water during their development, according to a study published Monday in the journal Nature Geoscience.

"By examining the age and oxygen isotopes in tiny crystals of the mineral zircon, we found unusually light isotopic signatures as far back as four billion years ago," said lead study author Hamed Gamaleldien, an adjunct research fellow in Curtin University's School of Earth and Planetary Sciences in Australia and an assistant professor at Khalifa University in the United Arab Emirates, in a news release.

"Such light oxygen isotopes are usually the result of hot, fresh water changing rocks many kilometres beneath the Earth's surface."

Gamaleldien believed that evidence of fresh water could only be explained by the presence of dry land, where water would accumulate and seep into the continental crust.

"We've got two crucial things here. "We discovered the earliest evidence of fresh water and representative evidence for dry land above the sea," he said.

The study suggests that the Earth's water cycle, which transports water between land, oceans, and atmosphere via evaporation and precipitation, was in operation at the time.

According to the authors, this finding indicates that the blueprint for the origins of life existed less than 600 million years after Earth's formation, much before dinosaurs or even the earliest known microbial life. Stromatolites, fossilised bacteria that built mounds in hot springs 3.5 billion years ago, provide the earliest commonly accepted proof of life—and fresh water, according to Gamaleldien.

Hugo Olierook, a senior research fellow at Curtin's School of Earth and Planetary Sciences, stated that the discovery sheds light on Earth's early history and suggests that landmasses and fresh water set the stage for life to flourish within less than 600 million years of the planet's formation.

He added: “The findings mark a significant step forward in our understanding of Earth’s early history and open doors for further exploration into the origins of life.”