Cloud Cities of Venus

Why so set on colonizing Mars? There’s better options.

Bespin, a planet from the Star Wars universe, is a gas giant with broad, habitable skies where inhabitants have developed cities. But this isn’t a concept that has to stay in science fiction.

Before we set our sights on the chalky red horizons of Mars, there was Venus. Named after the goddess of love and beauty, Venus is by no means a meek and pleasant planet. Beneath its wispy gold surface are rocky riverbeds and hellish, deserted plains. Acidic clouds roam over the valleys where oceans of carbon dioxide could have existed in the past, the immense pressure causing the gas to go into a liquid supercritical state. Its thick atmosphere has caused a runaway greenhouse effect with temperatures as high as 863 degrees Fahrenheit (462 degrees Celsius). If it’s described as Earth’s sister, it’s certainly not for its ability to host life. Instead the planet is a barren and suffocating landscape appearing as one of the brightest objects in our night sky.

And yet, Venus is in many ways a better option than Mars.

Up until about 60 years ago, we thought our future colonies would be built on Venus. It was close to the sun and had what appeared to be welcoming clouds in its sky. Similar in size and mass to Earth, scientists even thought it might already be home to alien life forms. It wasn’t until we sent probes that we realized just how hostile the planet really was. In fact, many of the first probes imploded in mid-air as they were subject to an atmospheric pressure 90 times higher than here on Earth. Later probes were reinforced and able to land on the Venusian surface, but even then they only lasted 2 hours before malfunctioning. We began to look for a better prospect.

But the problem with this thinking is that it only takes into consideration the planet’s surface. 31 miles (50 km) above, Venus has the most Earth-like conditions in the entire solar system. The pressure and temperature drops dramatically and the gravity is 90% of Earth’s or .9g. On Mars, gravity is a dangerous .4g, leading to a lot of complications for human settlers. Low gravity decreases muscle strength, affects coordination, and causes mineral loss in bones. Astronauts can experience drops in bone density of up to 1% per month. Even advanced cases of bone loss for elders here on Earth only see drops of 1% per year. Sometimes this bone loss can be irreversible. Not only that, in low gravity the cardiovascular muscles start to weaken and fluids shift towards your head where they can cause vision problems.

The tallest volcano on Venus, as photographed by NASA. The planet’s surface is continuously flooded by lava, dramatically affecting our ability to find traces of life.

Venus’s proximity is another advantage. It’s our closest neighboring planet and a roundtrip here could take half as long as one to Mars. This would not only cut costs but also lower exposure to radiation during travel. On the planet, Venus’s thick atmosphere is great at protecting from radiation all around, whereas this is another major concern on Mars whose thin atmosphere and lack of magnetic field would expose humans to extremely high levels of radiation.

While plans to colonize Mars involve protective domes, the colonies of Venus would be cloud cities. Floating structures and blimps made of light yet durable material (graphene, for example) would allow the cities to be mobile and resilient amidst Venus’s harsh winds. The blimps would be tiled overhead with solar panels that could collect energy. Because the planet is made almost entirely of CO2, any number of gasses could be used for flotation, including oxygen and nitrogen which are safe for human beings. That is to say, a blimp filled with regular Earth air would float well in the super-dense atmosphere. The sulfuric clouds contain hydrogen and water for crop irrigation and special suits would protect against the veils of acid.

Researchers estimate that cloud cities would, in many respects, be easier to set up than their Martian counterparts. Less material, more mobility, and great access to solar power means maintenance would be easier too, with Venus getting 4 times as much solar energy as Mars.

This potential spurred NASA’s HAVOC — or High Altitude Venus Operational Concept — which outlines the steps to colonizing the warm yellow skies. The first step would be a robotic test mission using a powerful rocket such as the Space Launch System currently in development. Two spacecraft, one without a crew and one with two people onboard, would take 100 days to arrive on Venus where the unmanned craft would promptly settle among the clouds and make sure the technology was safe and working appropriately. It would then be joined by the crew which would stay there for a full month before deploying a smaller capsule and coming back home. That is, of course, the downside to having a gravity similar to Earth’s: rockets must be powerful enough to break out of Venus’s hold. If the mission went well, a group of people would then be sent to live on our neighboring planet for a year. Altogether the mission would only take 450 days whereas a mission to Mars would last around 2 years.

Living on Venus would entail establishing 24 hour days. As of now, our sister planet has the slowest rotation in the solar system, meaning a single Venus day lasts 243 Earth days. This would interrupt the circadian rhythm that exists within us at the molecular level.

Despite what it is now, astrobiologists propose that Venus might have been the first habitable planet in the solar system. According to the most recent climate models, the planet should have been capable of hosting life for over half of its existence — meaning that if we don’t find traces of past organisms on the planet, it would make life on Earth an even bigger and more mysterious question. But it’s possible that there exist organisms there even today, living among the sulfuric clouds we would colonize. Microbes here on Earth have been known to live in acidic, extreme conditions not entirely different from those on Venus.

Why then this focus on the red planet when it appears to have more disadvantages than the nearby Venus?

There is this idea that Mars won out over Venus for one simple reason: a surface. From our days exploring continents and planting flags onto newfound shores, humankind has seen surfaces as a marker of innovation and discovery. We pursued a surface even in our venture to the moon with the iconic images of the American flag on lunar soil or the footprint left by the astronauts we greeted and cheered for along the way. Making history wouldn’t quite feel the same if we couldn’t touch the face of our home away from home. And should that be enough to leave cloud cities as a figment of our science fiction?