New evidence questions whether Venus ever had oceans on its surface

Recently, new research surprised astronomers and the public by suggesting that millions of years ago, Venus could have been a hospitable planet with lower temperatures allowing water to exist on its surface. That would have made it more Earth-like, and some people argued it could even have supported life.

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A composite image of the planet Venus as seen by the Japanese probe Akatsuki. Astronomers are debating whether this now-scorching planet could once have been cool enough for liquid water to exist on its surface. Image from the Akatsuki Orbiter, built by Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency

However, a new study of lava flows on the surface of Venus suggests these ideas are mistaken, and that Venus was not warm and wet after all. Researchers from the Lunar and Planetary Institute (LPI), part of the Universities Space Research Association (USRA), used data from observations of the planet to investigate how volcanic lava flowed over the surface.

Previously, scientists thought that the highlands on Venus were made of granite, the same as the continents here on Earth. Granite highlands require oceans of water in order to form, which is one reason scientists thought that the planet must have had surface water.

The LPI team looked at a volcanic flow in the Ovda Regio highlands region, using radar data to see how the flow moved. They found the flow was likely not made of granite as they had expected. In fact, it is likely made of basaltic lava. Basaltic lava does not require water to form, so while finding it doesn’t rule out the possibility of oceans on Venus, it does weaken some supporting evidence for the theory.

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A close-up of the lava flow in the Ovda Regio highlands region, with a dark line imposed on top to show the margin of the flow. NASA

“We know so little about Venus’ surface,” team member Dr. Allan Treiman, a USRA scientist at the LPI, said in a statement. “If the Ovda Regio highlands are made of basaltic rock as is most of Venus, they were likely squeezed up to their current heights by internal forces, possibly like mountains which result from plate tectonics on Earth.”

The findings have been published in a paper in the journal JGR Planets.

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