Earth formed 4.5 billion years ago, but it looked nothing like it did today.
Instead, it was a boiling hot, inhospitable world, pelted with incoming space rocks that rained down on the planet.
At some point in this early chaos, a Mars-sized rock crashed into Earth. The impact may have created the Moon, but it also transformed Earth's entire surface into a molten magma ocean.
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As that magma ocean cooled, it would have formed an atmosphere.
To figure out exactly what kind of atmosphere existed on Earth during that time, a team of scientists tried to recreate the Earth in miniature in the lab.
Their results, detailed in a study published in the journal Science Advances, revealed that Earth would have had an atmosphere similar to that of Venus today.
Hot, hellish and likely uninhabitable.
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In the experiment, the researchers heated a small rock to about 1900°C with a laser while it sat on top of a jet of gas. The small rock represented Earth in its molten state, and the gas acted like its atmosphere.
The model suggests the degassing of the molten ocean would have produced a dense atmosphere primarily made up of carbon dioxide and very little nitrogen, similar to the makeup of Venus' atmosphere.
But unlike Venus, Earth's mass and distance from the Sun allowed it to sustain liquid water on the planet's surface for prolonged periods of time.
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The water extracted the carbon dioxide from Earth's atmosphere, burying it deep into the planet's crust and mantle — rescuing Earth from becoming a scorching hot world like Venus.
If this process hadn't occurred, Earth would likely not been able to host life — and you wouldn't be reading this.