For centuries, humans have been wondering whether anyone lived on Venus. In the 1960s, telescopes delivered bad news: Modern-day Venus is thoroughly hostile to life, shrouded in thick acidic clouds and sweltering at 900°F. However, the question remained whether Venus started its life as a more habitable planet before a runaway greenhouse gas effect baked it dry.
But a new study from the University of Chicago argues there is little chance the planet was ever habitable.
By examining the composition of Venus’ atmosphere today and running simulations of its past to recreate those conditions, the researchers found very few scenarios in which the planet could have sustained liquid water and moderate temperatures for long.
“Our results suggest that Venus has been uninhabitable for at least 70% of its history—four times longer than some previous estimates,” said geophysical scientist Sasha Warren, a University of Chicago graduate student and first author of the paper, published in Proceedings of the National Academy of Sciences.
‘Earth and Venus could be cousins’
Humans love to speculate about traveling to other worlds; the earliest recorded mention of a writer describing a trip to Venus dates back to a second-century Syrian novel, and both Venus and Mars featured as lush tropical paradises in science fiction up until the 1960s.
It’s not such an unreasonable idea. Venus is a similar size as Earth and appears to have similar amounts of carbon, and in the past the sun was not as bright, meaning more moderate surface temperatures.
“From a great distance, Earth and Venus could be cousins,” said UChicago planetary scientist and associate professor Edwin Kite, the other co-author on the paper. “They’re both rocky and similar distances from the sun. But clearly they have had extremely different outcomes as far as habitability goes.”
As we discover more and more planets orbiting distant stars, scientists are very interested in understanding what factors influence a planet’s climate and habitability.
The trouble is that even though Venus is close to us, the planet keeps its secrets. Venus’ extremely hot surface means no landing crafts have lasted longer than a couple of hours, and volcanic eruptions have obliterated most evidence from ancient rocks.