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The Earth’s early atmosphere was possibly poisonous like that on Venus

By Leah Crane

An illustration of the early Earth that may have had a toxic atmosphere like today’s Venus

Shutterstock / Diego Barucco

When the earth was young, its surface was likely covered in an ocean of magma, and the gases rising from this seething sea may have given it an atmosphere almost identical to the poisonous one present on Venus today .

Earth’s early magma ocean was likely created by a collision with a Mars-sized object that melted much of the young planet and created the moon. As the magma ocean cooled, some compounds from the molten mixture would have condensed and formed an atmosphere.

To find out what this atmosphere would have been like, Paolo Sossi from ETH Zurich in Switzerland and his colleagues used a technique called aerodynamic levitation to levitate a small rock pellet on a gas jet and heat it to around 1900 ° C with a laser to melt it.

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“This little molten marble, floating at almost 2000 degrees, is a kind of miniature earth in a molten state,” says Sossi. The gas flowing around the marble behaves like a miniature atmosphere.

The researchers repeated the experiment, changing the composition of the gas jet by adding and removing various compounds to determine the likely composition of the young earth atmosphere. The oxygen content in the molten sample changed depending on the composition of the gas. They compared these molten marbles to rock samples from the Earth’s mantle to determine which atmosphere best suited our geological record.

They found that this was a dense atmosphere full of carbon dioxide and relatively low in nitrogen, similar to the atmosphere on Venus today. The Martian atmosphere has almost the same composition, although it is much thinner.

The fact that Earth is larger than Mars – which means it has enough gravity to hold its atmosphere in place – and cooler than Venus, kept liquid water on its surface, extracted carbon dioxide from the atmosphere, and prevented the Planet went through the runaway greenhouse effect. This Venus experienced a sultry landscape of hell.

Journal reference: Science Advances, DOI: 10.1126 / sciadv.abd1387

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