[meteorite-list] Did Venus Have Carbon Dioxide Oceans?

[Ron Baalke]

http://www.scientificamerican.com/article/did-venus-have-carbon-dioxide-oceans/

Did Venus Have Carbon Dioxide Oceans?

Simulations suggest Venus could have once harbored seas of supercritical 
carbon dioxide

By Charles Q. Choi and SPACE.com
December 29, 2014 

Venus may have once possessed strange oceans of carbon dioxide fluid that 
helped shape the planet's surface, researchers say.

Venus is often described as Earth's twin planet because it is the world 
closest to Earth in size, mass, distance and chemical makeup. However, 
whereas Earth is a haven for life, Venus is typically described as hellish, 
with a crushing atmosphere and clouds of corrosive sulfuric acid floating 
over a rocky desert surface hot enough to melt lead.

Although Venus is currently unbearably hot and dry, it might have once 
had oceans like Earth. Prior research suggested that Venus possessed enough 
water in its atmosphere in the past to cover the entire planet in an ocean 
about 80 feet deep (25 meters) — if all that water could somehow fall 
down as rain. But the planet was probably too warm for such water to cool 
down and precipitate, even if the planet did have enough moisture. [The 
Weirdest Facts About Venus]

Instead of seas of water, then, scientists now suggest that Venus might 
have once possessed bizarre oceans of carbon dioxide fluid.

Carbon dioxide is common on Venus.

"Presently, the atmosphere of Venus is mostly carbon dioxide, 96.5 percent 
by volume," said lead study author Dima Bolmatov, a theoretical physicist 
at Cornell University in Ithaca, New York..

Most familiar on Earth as a greenhouse gas that traps heat, helping warm 
the planet, carbon dioxide is exhaled by animals and used by plants in 
photosynthesis. 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.

To see what the effects of supercritical carbon dioxide on Venus might 
be, Bolmatov and his colleagues investigated the unusual properties of 
supercritical matter. A great deal remains uncertain about such substances, 
he said.

Scientists had generally thought the physical properties of supercritical 
fluids changed gradually with pressure and temperature. However, in computer 
simulations of molecular activity, Bolmatov and his colleagues found that 
supercritical matter could shift dramatically from gaslike to liquidlike 
properties.

The atmospheric pressure on the surface of Venus is currently more than 
90 times that of Earth, but in the early days of the planet, Venus' surface 
pressure could have been dozens of times greater. This could have lasted 
over a relatively long time period of 100 million to 200 million years. 
Under such conditions, supercritical carbon dioxide with liquidlike behavior 
might have formed, Bolmatov said.

"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 researchers found that depending on the pressure and temperature, 
clusters of gas-like supercritical carbon dioxide might have formed in 
this supercritical carbon dioxide on Venus that "looked like soap bubbles," 
Bolmatov said. "A bubble of gas that is covered by a thick layer of liquid."

Bolmatov and his colleagues said they now hope to conduct experiments 
to detect this shift from gaslike to liquidlike properties in supercritical 
carbon dioxide. The scientists detailed their findings in the Aug. 21 
issue of the Journal of Physical Chemistry Letters.

Original article on Space.com.