3.7 billion year-old rocks from Greenland may hold secrets of life on Earth

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Earth hasn’t always been an oasis of blue and green life in an otherwise inhospitable solar system. During our planet’s first 50 million years, roughly 4.5 billion years ago, its surface was a hellish landscape of magmatic oceans, bubbling and belching with the heat of the Earth’s interior.

The subsequent cooling of the planet from this molten state and the crystallization of these magmatic oceans into solid rocks was a critical step in assembling our planet’s structure, the chemistry of its surface, and the formation of its early atmosphere. .

It was speculated that these primitive rocks, containing clues that could explain the habitability of the Earth, had been lost due to the ravages of plate tectonics. But now my team have discovered the chemical remnants of Earth’s magmatic oceans in 3.7 billion-year-old rocks in southern Greenland, revealing a tantalizing snapshot of a time when Earth was almost completely melted.

Hell on earth

Earth is the product of a chaotic early solar system, which is said to have exhibited a number of catastrophic impacts between Earth and other planetary bodies. The formation of the Earth culminated in its collision with a Mars-sized impactor planet, which also resulted in the formation of the Earth’s moon about 4.5 billion years ago.

These cosmic clashes are believed to have generated enough energy to melt the earth’s crust and almost all of our planet’s interior (mantle), creating planetary-scale volumes of molten rock that formed “magmatic oceans.” Hundreds of kilometers deep. Today, on the other hand, the earth’s crust is entirely solid, and the mantle is considered a “plastic solid”: allowing slow and viscous geological movement away from the liquid magma of the earth’s first mantle.

As Earth recovered and cooled from its chaotic collisions, its deep magmatic oceans crystallized and solidified, beginning Earth’s journey to the planet we know today. Volcanic gases escaping from Earth’s cooling magmatic oceans may have played a decisive role in the formation and makeup of our planet’s primitive atmosphere – which would eventually support life.

Layers of the Earth in cross section, showing the core, mantle and crust