Discovery of early fresh water on Earth challenges longstanding theory of life’s origins

(CN) — Evidence of fresh water deep inside Earth has thrown a wrench in scientists' longstanding theory of a salty, ocean-smothered Earth existing four billion years ago.

Fresh water, which is essential to life, appeared 500 million years earlier than previously thought, according to a study published Monday in the journal Nature Geoscience.

Proponents of the "water world" theory have long held that Earth was once enveloped by a global ocean with little visible land. A 2021 Harvard University study supported the idea, suggesting Earth's primordial ocean could have covered the entire surface three to four billion years ago.

Life may have originated in warm springs on the ocean floor, according to the theory — such as the hydrothermal vents called "black smokers" discovered in 1980 near Cabo San Lucas, Mexico.

By analyzing ancient crystals from the Jack Hills in western Australia, however, researchers from Curtin University discovered fresh water on Earth just a few hundred million years after the planet's formation.

Researchers looked at the age and oxygen isotopes in small zircon crystals using the CAMECA 1300HR3 instrument at Curtin’s John de Laeter Centre’s Large Geometry Ion Microprobe facility.

They discovered that these crystals had very light isotopic signatures dating back four billion years. These light isotopes usually happen when hot, fresh water changes rocks deep below Earth's surface, several kilometers down.

“Evidence of fresh water this deep inside Earth challenges the existing theory that Earth was completely covered by ocean four billion years ago,” said Hamed Gamaleldien, adjunct research fellow at Curtin’s School of Earth and Planetary Sciences in Australia, in a press release announcing the research.

According to study co-author Hugo Olierook from Curtin University’s School of Earth and Planetary Sciences, the presence of fresh water in Earth’s early history provided the conditions necessary for life to emerge.

“This discovery not only sheds light on Earth’s early history but also suggests that 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,” Olierook said in the release.

“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.”