Why Venus is dry, new study explains

NEW DELHI: Venus, our neighbouring planet and closer to the Sun, is dry because the hydrogen in its atmosphere gets lost into space, thereby robbing the planet of one of the two elements needed for water to form, according to new research. Co-lead author and a research scientist at the University of Colorado Boulder, US, Eryn Cangi, described Venus to be “positively parched.”
“If you took all the water on Earth and spread it over the planet like jam on toast, you’d get a liquid layer roughly 3 kilometres deep.
“If you did the same thing on Venus, where all the water is trapped in the air, you’d wind up with only 3 centimetres, barely enough to get your toes wet,” she explained.
However, Venus wasn’t always such a desert, the researchers said.
When Venus was formed about a billion years ago, the planet received about as much water as Earth. But at some point, a powerful greenhouse effect was kicked off by clouds of carbon dioxide in the planet’s atmosphere, raising temperatures to a “roasting” 500 degrees Celsius, they explained.
The catastrophe led to all of Venus’s water being evaporated into steam and most of it drifted off into space, the authors said. Their study is published in the journal Nature.
However, the ancient evaporation cannot explain why Venus is as dry as it is today, or why the planet continues to lose its water, they said.
In the latest study, using computer simulations, the researchers found the “culprit” to be a molecule found in the planet’s upper atmospheres, formed when water mixes with carbon dioxide and symbolised as HCO+.
While the molecule is constantly produced, being positively charged, electrons in the atmosphere find them and bond with them to split the charged molecules into two.
“In the process, hydrogen atoms zip away and may even escape into space entirely – robbing Venus of one of the two components of water,” the researchers said.
Termed as “dissociative recombination”, the process is causing Venus to lose roughly twice as much water every day compared to previous estimates, they said.
While scientists have never observed the molecule HCO+ in Venus’s atmosphere, the study authors suggested it was because “they’ve never had the instruments to properly look.”
They said that future missions to Venus might detect the molecule, revealing another key piece of “the story of water on Venus.”
The findings reveal new hints about why Venus, which probably once looked almost identical to Earth, is all but unrecognizable today, according to Cangi.