With its runaway climate-change and roiling, toxic atmosphere, Venus would be a pretty unpleasant place for humans to inhabit in its current state. Its atmosphere is dense with poisonous carbon dioxide and nitrogen, and howling with 200 mph winds. Its surface is a furnace with an average temperature of 864 degrees Fahrenheit.
But the second planet from the sun—nicknamed the “Evening Star” due to its bright appearance in Earth’s own sky—is roughly the same size as Earth and may have once had a climate like our own planet’s. It’s a world that’s worth exploring and maybe even living on, if only we could breathe there.
Never fear, NASA has a plan. Well, a loose sketch of a plan.
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The idea, proposed by Alex Howe, an astrophysicist at NASA’s Goddard Space Flight Center in Maryland, is to construct vast, porous structures—rafts, in essence—that, because they’re less dense than the air underneath, would float above the most toxic layers of Venus’s atmosphere. A preprint of Howe’s study appeared online on March 15, and has been peer-reviewed and published in the February issue of the Journal of the British Interplanetary Society (though it is not yet available online.)
Howe’s scheme is ambitious and costly to the point of absurdity. Even if it was greenlighted and funded, it might take 200 years from start to finish. But technically speaking, it’s “very much a possibility,” Janusz Petkowski, an astrobiologist and expert on Venus at MIT, told The Daily Beast.
The connected rafts, made up of hollow linked sections the size of city blocks and together forming a flexible surface, would have to cover the entire planet. Powerful machines could begin to alter the air above into a mix that’s breathable by people. Changing the hotter, more noxious, and windier air below the rafts would be a longer-term project.
Once the top layer of air is breathable, people could live and work on top of the rafts. From there, scientists and engineers could closely study Venus and its hot, carbon-dioxide-and-nitrogen atmosphere, perhaps probing its past in order to explain why a planet that was once a lot like Earth became a poisonous hellscape.
But the main justification for building these “cloud cities” on Venus isn’t for near-term science. If it was, “remote and robotic probes would make much more sense,” Dirk Schulze-Makuch, an astrobiologist at the Technical University Berlin, told The Daily Beast.
No, the main rationale is emotional. “The interest lies primarily in the spirit of exploration,” Howe told The Daily Beast. The moon and Mars are likelier candidates to host humanity’s first permanent off-world colonies. But as a new home for our species, Venus has a certain appeal. Howe emphasized Venus’s “near-Earth-like surface gravity, an atmosphere thick enough to provide robust protection from cosmic rays and UV radiation compared with Mars and shorter travel time from Earth.”
A newly processed image of Venus that combines older data with modern image processing software.
NASAHowe’s cloud cities could start with robotic probes carrying solar-powered machines to Venus. The highly autonomous machines would suck in carbon dioxide and spit out oxygen and carbon. We’d store the oxygen for future use while using the carbon to build 300-foot-wide, hollow tiles with enough empty space inside to make them very light. Indeed, light enough to float.
The great thing about mining carbon from Venus’ unbreathable atmosphere is that taking out all that carbon begins to change the chemical makeup of the air. It eventually becomes a mix of oxygen and nitrogen that people can breathe, starting with the lighter upper layer.
Link those carbon tiles together and we could cover the entire planet at an altitude of 30 miles or so—high enough to get above the worst of the planet’s brutal winds and heat.
Here’s the rub: Howe calculated it would take 72 trillion tiles to complete the sprawling, floating, planetary foundation. And we’d have to keep making new tiles in order to replace ones that break—most likely from wind shear—while also patching holes resulting from occasional asteroid impacts.
And of course, the project wouldn’t just end there. Once we’ve got our foundation tiles, we’d start adding layers until we’ve built up a continuous surface thousands of feet thick—and remaining hollow. We can store all that extra oxygen, the byproduct of our carbon-mining, inside the hollow ground, at least until it becomes a fire hazard.
The first few colonists could emigrate from Earth to Venus before the thicker surface is complete. They’d live in enclosed domes, where they could help oversee the ongoing construction.
But let’s imagine we’ve spent trillions of dollars and, after a century or so, built rafts 30 miles over the Venusian surface. We’re still not even ready to send in the rest of the new colonists to Venus, because they’d have nothing to drink. “Water is very scarce on Venus,” Petkowski explained.
That’s the one major commodity we’d have to import from off-world. Sustaining cities, farms and natural biomes on Venus could require a volume of water equal to a cube with sides 40 miles long. That’s a lot of water. As in, more than a quadrillion gallons.
Howe proposed that, for starters, we stripmine ice from Ceres, a chilly dwarf planet in the asteroid belt between the orbits of Mars and Jupiter. We’d build an enormous elevator on the surface of Ceres and slowly lift the bulky, heavy ice into space, where rockets, most likely built and fueled at nearby human outposts, would nudge it toward Venus.
Ceres, which is believed to hold vast water ice reserves.
NASABut Ceres would eventually run out of mineable ice. “It appears that the majority of the water used to terraform Venus will have to be delivered from either Earth or Mars,” Howe conceded.
There are obvious reasons you might not want to remove a significant portion of Earth’s water. That leaves Mars.
Despite appearances, Mars might actually be a fairly wet planet. The water that once formed oceans on Mars now lies underground at the north and south poles, mostly in the form of ice.
We’d have to remove a lot of it in order to make Venus habitable on a planet-wide basis. So much that we’d actually make Mars lighter, thus altering its spin and making its day 20 seconds longer. The extra-long day wouldn’t have any practical impact on our efforts to explore or eventually colonize Mars. It’s just indicative of the scale of ice we’d have to remove from Mars in order to terraform Venus.
The vast water-exporting operation would require extensive infrastructure designed to reorganize all the water on the Red Planet. “For that reason, a large-scale terraforming effort on Mars would likely need to be underway to undertake the task on Venus,” Howe wrote.
Once all the surfaces are in place, the Venusian air has breathable oxygen, and water is flowing, the main body of colonists could finally rocket in. They could establish farms and even import Earth-like biomes. We could have forests teeming with animals, and lakes full of fish.
It’s an incredible vision. But it will almost certainly remain just a vision. Try selling it to the lawmakers in spacefaring countries who would have to appropriate the countless trillions of dollars it would take to even begin undertaking a project of this magnitude.
This also isn’t the first time someone has proposed habitats that could float above the Venusian clouds. A separate, much more modest proposal for blimp-like enclosed colonies on Venus, drawn up by scientists at NASA’s Langley Research Center in Virginia back in 2018, came and went without anyone spending a dime on it.
John Logsdon, founder of the Space Policy Institute at George Washington University, told The Daily Beast four years ago that a project aimed at colonizing Venus had “essentially no chance of being implemented in the foreseeable future."
So far, he’s right. But maybe in a century or two, Venus will look a lot more appealing as a second home for humanity.
Correction 3/29: The original version of this story incorrectly stated that Howe’s study was not yet peer-reviewed. We regret the error.
