Evidence of Earth's oldest rains discovered Evidence of Earth's oldest rains discovered

Evidence of Earth's oldest rains discovered

Evidence of Earth's oldest rains discovered
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A new study has found that fresh water first spread across the Earth's surface approximately 4 billion years ago, 500 million years earlier than previously thought.

A team of researchers in Australia and China used oxygen isotopes trapped in ancient minerals to date the first signs of fresh water on our planet.

The researchers pointed to the Jack Hills Mountains in Western Australia, which contain the oldest surviving material from the Earth's crust, where primitive minerals remained relatively unchanged for 4.4 billion years, due to heat and pressure.

There, the team found evidence of Earth's oldest rains trapped inside rocky Hadean zircon crystals, representing a major change in our understanding of the planet's hydrological history.

“By examining the age and oxygen isotopes in small crystals of the mineral zircon, we found unusually light isotopic signatures dating back to 4 billion years ago,” says geologist and lead author, Hamed Gamal El-Din, from Curtin University in Australia.

Jack Hills zircons have "isotopically very light" compositions that are only possible if they formed beneath the mantle and were also exposed to fresh water, specifically meteoric water. 

“These light oxygen isotopes are usually the result of hot fresh water altering rocks several kilometers below the Earth’s surface,” says Jamal El-Din. “Evidence of fresh water at this depth within the Earth challenges the current theory that the Earth was completely covered by oceans 4 years ago.” Billions of years."

"This discovery not only sheds light on Earth's early history, but also suggests that land masses and fresh water paved the way for life to flourish over a relatively short period of time - less than 600 million years after the planet formed," says co-author Hugo Ollerock.

This study highlights that drylands, freshwater reservoirs, the water cycle, and perhaps even life on Earth, appeared much earlier than we thought.

The study was published in the journal Nature Geoscience.

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