Unable To Form Oceans, Venus Became A Wasteland: Scientists

Venus may be a sweltering wasteland today, but scientists have questioned whether the planet was always so inhospitable. While previous studies suggested Venus might have once been covered in oceans, new research has found the opposite: Venus has likely never been able to support oceans, Ashley Strickland reported for CNN.

Photo Insert: A rendering of Venus

Researchers also determined that a similar story could have played out on Earth as well had things been just a bit different. Venus, our closest planetary neighbor, is called Earth's twin because of the similarity in size and density of both planets. Otherwise, the planets differ radically.

While Earth is a natural hub for life, Venus is a lifeless planet with a toxic carbon dioxide atmosphere 90 times thicker than ours, clouds of sulphuric acid, and surface temperatures that reach 864 degrees Fahrenheit (462 degrees Celsius) -- hot enough to melt lead.

To understand how these two rocky planets turned out so differently, a team of astrophysicists decided to try to simulate the beginning, when our solar system's planets formed 4.5 billion years ago.

They used climate models -- similar to what researchers use when simulating climate change on Earth -- to peer back in time at young Venus and Earth. Their new study published Wednesday in the journal Nature. More than 4 billion years ago, Earth and Venus were piping hot and covered in magma.

Oceans can only form when temperatures are cool enough for water to condense and fall as rain over thousands of years. That's how Earth's global ocean formed over tens of millions of years. Venus, on the other hand, remained hot. At the time, our sun was about 25% fainter than it is now.

But that wouldn't have been enough to help Venus cool off, since it's the second-closest planet to the sun. The researchers questioned whether clouds could have played a role in helping Venus cool down. Their climate model determined that clouds did contribute, but in an unexpected way.

They clustered on the night side of Venus where they wouldn't have been able to shield the planet's dayside from the sun. While Venus is not tidally locked to the sun, where one side of the planet always faces the star, it has an extremely slow rotation rate.

Rather than shielding Venus from heat, the night side clouds contributed to a greenhouse effect that trapped heat within the planet's dense atmosphere and kept temperatures high. With such consistent, trapped heat, Venus would have been too hot for rain to fall. Instead, water could only exist as its gaseous form, water vapor, in the atmosphere.

"The associated high temperatures meant that any water would have been present in the form of steam, as in a gigantic pressure cooker," said Martin Turbet, lead study author, researcher at the University of Geneva's Department of Astronomy of the Faculty of Science and member of the National Centre of Competence in Research Planets, Switzerland, in a statement.

Things could have turned out the same way for Earth if our planet had been slightly closer to the sun or if the sun was as bright back then as it is now. Because the sun was dimmer billions of years ago, Earth was able to cool down enough from its molten state for water to form and create our global ocean. The faint young sun "was a key ingredient to actually form the first oceans on Earth," Turbet wrote in an email.

WEEKLY FEATURE : MVP Group Keeps Lights On During Pandemic