Venus may be hiding a sea of magma under its surface that could help us learn about Earth鈥檚 deep past.
Venus and Earth are a similar size, made of similar materials and are next-door neighbours in the solar system. When these planets first formed, they were probably both molten, with what might have been magma oceans on their surface.
Over billions of years, their crusts solidified, leaving a layer of magma underneath a stony shell. Earth鈥檚 magma ocean hardened into rock about 2 billion years ago, but Venus鈥檚 may remain.
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The biggest difference between Earth and Venus is that our planet has plate tectonics, which cycles cool material from the surface towards its core. Venus, however, doesn鈥檛 have plate tectonics, so its interior should be hotter than Earth鈥檚.
Joseph O鈥橰ourke at Arizona State University how Venus鈥檚 interior cooled over time. 鈥淓ven though Earth and Venus are made of the same stuff and similar sized, Venus cools down about half as fast because it isn鈥檛 cycling cold material from the surface down to the interior,鈥� says O鈥橰ourke.
He calculated that because of this, Venus could still have an underground magma ocean more than 200 kilometres thick 鈥� about 2 per cent of the planet鈥檚 diameter 鈥� surrounding its entire core. The research was to have been presented at the now-cancelled Lunar and Planetary Science Conference in Texas.
Venus may now be going through the same process that Earth did billions of years ago: the magma ocean is slowly cooling and solidifying. This should take another 2 billion years at least, says O鈥橰ourke, and studying it could help us understand how Earth evolved as its own molten layer cooled off.
To confirm that this ocean exists, we will have to send an orbiter to Venus to measure how the planet is stretched by the sun鈥檚 tidal forces. This will differ depending on whether Venus is hiding a sea. Both NASA and the European Space Agency have missions in the works to send an orbiter.
鈥淰enus is sort of the once-and-future Earth,鈥� says O鈥橰ourke. 鈥淚t looks like Earth did in the past when it was super-hot and it also might be a preview of Earth in the future if we have a runaway greenhouse effect and all of the oceans boil.
鈥淚f we go out and find a magma ocean on Venus, that will inform how we understand Earth鈥檚 history.鈥�
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