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

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

The subsequent cooling of the planet from this molten state, and the crystallization of these magma oceans into solid rock, was a defining stage in the assembly of our planet’s structure, the chemistry of its surface, and the formation of its early atmosphere.

These primeval rocks, containing clues that might explain Earth’s habitability, were assumed to have been lost to the ravages of plate tectonics. But now, my team has discovered the chemical remnants of Earth’s magma oceans in 3.7 billion year-old rocks from southern Greenland, revealing a tantalizing snapshot of a time when the Earth was almost entirely molten.

Hell on Earth

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

These cosmic clashes are thought to have generated enough energy to melt the Earth’s crust and almost all of our planet’s interior (the mantle), creating planetary-scale volumes of molten rock that formed “magma oceans” hundreds of kilometers in depth. Today, in contrast, Earth’s crust is entirely solid, and the mantle is seen as a “plastic solid”: allowing slow, viscous geological movement a far cry from the liquid magma of Earth’s early mantle.

As the Earth recovered and cooled after its chaotic collisions, its deep magma oceans crystallized and solidified, beginning Earth’s journey to the planet we know today. The volcanic gases which bubbled out of Earth’s cooling magma oceans may have been decisive in the formation and composition of our planet’s early atmosphere – which would eventually support life.