Earth may have always held the key ingredients for life

How did life on Earth begin? People have been asking that for ages. The answers remain scattered across rocks, oceans, and ancient landscapes. One clue hides in an essential ingredient for life – phosphorus.

Phosphorus is everywhere in living things. It holds together DNA and RNA. It forms the framework of cell membranes. No life can grow or function without it.

Yet, phosphorus mostly stays trapped in rocks. It hides inside phosphate minerals, which barely dissolve in water. That raises an old and puzzling question: how did early Earth get enough phosphorus to spark life?

Yuya Tsukamoto and Takeshi Kakegawa from Tohoku University took that question seriously. They decided to look where most people wouldn’t – deep under the sea, in rocks that are billions of years old.

Key element for life on Earth

The researchers focused on the Pilbara Craton in Western Australia, which holds some of the oldest known seafloor rocks.

The rocks are an astonishing 3.455 billion years old. The team’s discovery wasn’t subtle. It jumped out from the data.

“We analyzed 3.455-billion-year-old basaltic seafloor rocks in drill core samples recovered from the Pilbara Craton, Western Australia, discovering that P was significantly leached from the hydrothermally altered rocks compared to the least altered rocks,” explained Tsukamoto.

He noted that further mineralogical analyses indicated that phosphate minerals had undergone dissolution in rocks where P was depleted.

Simply put, hot fluids moved through these rocks and pulled phosphorus out. That phosphorus didn’t just disappear. It entered the surrounding seawater, turning parts of the ocean into phosphorus-rich zones.

Tracking the source of phosphorus

The rocks alone didn’t tell the whole story. The team wanted to understand what made this phosphorus release possible. They uncovered two kinds of hydrothermal fluids that shaped this process.

One type was hot, rich in sulfur, and capable of breaking down minerals quickly. The other was more surprising – mildly acidic to alkaline fluids at lower temperatures.

These fluids were common in the Archean era because Earth’s atmosphere back then was filled with carbon dioxide. That unique atmosphere made these fluids react in unexpected ways with the rocks.

The result? Massive amounts of dissolved phosphate in the water. The numbers were shocking. These fluids could carry up to 2 millimolar phosphate – nearly 1,000 times higher than what’s found in modern seawater.

Suddenly, early Earth wasn’t a barren place. Its oceans were filled with phosphorus.

Earth’s oceans held elements for life

This wasn’t just a chemistry experiment. The results changed how scientists think about early Earth. The researchers calculated how much phosphorus these underwater systems could release.

The findings were stunning. The amount of phosphorus released into the oceans by these hydrothermal systems could match, or even exceed, the amount entering modern oceans through rivers and weathering of land rocks.

“Importantly, this study provides direct evidence that submarine hydrothermal activity leached P from seafloor basaltic rocks and quantifies the potential P flux from these hydrothermal systems to the early ocean,” adds Tsukamoto.

Imagine ancient oceans filled with nutrients. These phosphorus-rich waters may have supported some of Earth’s earliest microbial life.

The ancient communities didn’t need a vast, lush planet. It only needed these hidden underwater environments to get started.

Hot springs and hidden worlds on land

The study also pointed to something beyond the oceans – hot springs on land. Hydrothermal systems aren’t just found under the sea. They exist on land too, in places like hot springs.

These environments might have also released phosphorus on early Earth. That means life’s building blocks weren’t limited to deep-sea vents. They could have existed in steaming pools on land.

This opens the door for more discoveries. Scientists now plan to study how phosphate behaves in rocks across different periods of Earth’s history. By tracing phosphorus through time, they hope to unlock new chapters of Earth’s story.

The message is clear: Life’s ingredients may have come from places on Earth we’ve only just begun to explore. Deep beneath the waves, within rocks touched by ancient fluids, the story of life may have quietly begun.

The study is published in the journal Geochimica et Cosmochimica Acta.

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