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Venus Was Once Awash in Oceans of Carbon Dioxide

The planet’s pressure and temperature created a supercritical state where carbon dioxide has properties of a liquid and a gas

Venus's southern hemisphere (NASA/JPL/USGS/Michael Benson)
smithsonian.com

Venus is a weird planet. At the surface, under a rapidly spinning atmosphere, it’s hot enough to melt lead, and pressure climbs to more than 90 times that on Earth. It also "snows" metal. Now, new research adds just one more strange, extreme phenomenon to Venus' litany—the planet once had oceans of liquid carbon dioxide, reports Charles Q. Choi for Space.com

Already researchers suspected that Venus’s atmosphere once held an abundance of water—enough to cover the planet in an ocean 80 feet deep. But it wouldn’t have been cool enough for the clouds to release their water as rain. Instead, carbon dioxide might have gathered on the surface, scientists say in a report published in the Journal of Physical Chemistry Letters

"Presently, the atmosphere of Venus is mostly carbon dioxide, 96.5 percent by volume," lead study author Dima Bolmatov, a theoretical physicist at Cornell University in Ithaca, New York, told Space.com. Choi explains that that CO2 didn’t rain down:

While the substance can exist as a solid, liquid and gas, past a critical point of combined temperature and pressure, carbon dioxide can enter a "supercritical" state. Such a supercritical fluid can have properties of both liquids and gases. For example, it can dissolve materials like a liquid, but flow like a gas.

Earlier in Venus’s history, the atmosphere could have pressed down even more aggressively than it does today. That could have created oceans of supercritical carbon dioxide. "This in turn makes it plausible that geological features on Venus like rift valleys, riverlike beds, and plains are the fingerprints of near-surface activity of liquidlike supercritical carbon dioxide," Bolmatov told Space.com.

The weird ancient oceans of the second planet from the sun aren’t the only extreme landscapes on other solar system bodies. Titan has seas and lakes that are a mix of methane, ethane and other hydrocarbons, for example. Of course, we remain interested in finding oceans of liquid water, because they might harbor life. But learning about Venus’s strange history and environment will be relevant if we want to plan future missions to Venus

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