Unlike its present infernal landscape, planet Venus may have once been a habitable planet with a protective, Earth-like atmosphere, a new study suggests.
It has long been proposed that Venus was born out of the same ingredients that make up Earth, but the planet diverted to a different evolutionary path. Now, the findings of the new report may draw up comparisons and similarities between the two worlds.
Modern Venus is a hellish world where temperatures spike up to 462 degrees Celsius (864 degrees Fahrenheit) at the surface. Because there is almost no water vapor on the planet, carbon dioxide (CO2) accumulates on its extremely thick atmosphere.
In the 1980s, however, NASA's Pioneer mission suggested that there may have been an ocean on Venus before. This began the emergence of hints that point to the planet's potential habitability in the past.
Scientists say that because Venus is the second closest planet to the sun and receives an intense amount of sunlight, its early oceans might have evaporated.
The water vapor molecules might have been broken apart by ultraviolet radiation and the hydrogen then escaped into space. And as CO2 gathered into the atmosphere over time, a runaway greenhouse effect formed current conditions.
Venus' Rotation vs. Earth's Rotation
Past research suggests that the speed of a planet's rotation on its axis affects its climate habitability. It was theorized that a thick atmosphere — present conditions on Venus — was needed for a planet to have a slow rotation rate.
However, new studies have shown that a thin atmosphere — present conditions on Earth — could have produced the same result. This means that an ancient Venus with an atmosphere like that of modern Earth could have had the same rotation rate that modern Venus possesses, researchers said.
Protective Conditions On Ancient Venus
Scientists from NASA's Goddard Institute for Space Studies (GISS) created a simulation of a hypothetical ancient Venus with an Earth-like atmosphere — where one Venus day is equivalent to 117 Earth days — and a shallow ocean consistent with information from the Pioneer mission records.
In the end, astronomers found that the slow spin on Venus exposes its dayside to the sun for two months at a time. According to study co-author Anthony Del Genio, the slow rotation causes the surface to warm and produces rain that creates thick layers of clouds.
"[This] acts like an umbrella to shield the surface from much of the solar heating," said Del Genio, who is also a GISS scientist.
Because of the rotation and the thick clouds, the average climate temperatures on ancient Venus were a few degrees lower than that on modern Earth, he added.
Details of the new study are shared in the journal Geophysical Research Letters.