In fact, people traveling to Venus someday could be listening to recorded greetings like this:

"Welcome to Ishtar, your gateway to the always-sunny Cytherean skies! The time is eleven twenty-seven AM, Standard Cytherian Time. Ambient air pressure is regular one-hundred and one kilopascals, inside and outside the domes, and external temperatures are an even three-hundred Kelvin.

"Please have your ID ready for scan and be sure to include the results of your bio-scan. If you have not received this complimentary service aboard our liner, we encourage you to avail yourself of one of the booths located throughout the atrium.

"We would like to remind our new arrivals that the days are rather long here on Venus. Just less than 117 days long, in fact. We advise that you use your personal solar shade every 16 hours to ensure the soundness of sleep. This will also ensure that you remain acclimated to a 24-hour schedule.

"Would it interest you to know that since we first settled the skies, less than one-hundred and seventy-five days have passed? You could say that in the more than 56 Earth years since Ishtar was established, time has moved a little slower for us!

"A reminder to all patrons to exercise extreme caution when transferring from the colony to their airship. The windows and docking collar are secured for your protection, but please refrain from placing any weight or knocking on them. Once you're on board, please sit back, relax, and let us transport you across a landscape of clouds! 

Source: Kevin M Gill

Sounds pretty neat, doesn't it? To travel to a world where the cities are floating atop dense clouds and all transit is handled by airships drifting from one place to another. But wait, there's more! With a few more centuries of work, these floating cities could transform the atmosphere and surface of Venus. If that's the case someday, welcoming messages could sound more like this:

"Welcome to Pythagoras station, your gateway to Venus, ocean paradise of the Solar System! The date is Sol Kukulkan, Cliodhna twenty-fifth, and the hour is 10.30am Niobia Planitia time. The temperature is a balmy three-hundred Kelvin, and air pressure is an even 100 kilopascal. We thank you for making Venus your vacation destination and hope you find endless relaxation on the ceaseless shorelines and boundless seas.

"As you travel down the Beanstalk, you will notice the gravity slowly shifting. We assure you that this is entirely normal and something our safety procedures are prepared for. Once you reach the surface, you will experience gravity that is about 90% of Earth-normal, which will make for an easy adjustment.

"Enjoy that extra spring in your step, knowing that it will not cost you any muscle or bone density! We have also managed to speed up the planet's rotation so that a day on Venus is the same as a day on Earth. Just another amenity that terraforming has made possible here on our world!

"Be sure to familiarize yourself with the rules and regulations regarding the importation of fauna, which includes microbes. For your convenience, decontamination booths have been placed throughout the installation. Bathing or contact of any kind with the Cytherean oceans is forbidden to patrons who have not decontaminated. Our ocean ecosystems are still evolving, and we ask that you respect the local biodiversity.

"Be sure to familiarize yourself with your accommodation package. Once you reach the surface, you will need to select the proper ferry. Our ocean-going liners offer transportation services to the continents of Ishtar, Aphrodite, and Lada Terra. Once there, you will be able to book passage to your desired maritime resort or island retreat."

Venus is beautiful!

For generations, humans have been fascinated by Venus, the brightest star in the night and morning sky. Because of the nature of its appearance, where it disappears for days at a time and then appears to emerge on the other side of the Sun, it was long thought to be two different stars – the 'Morning Star' and the 'Evening Star'.

It was not long before ancient astronomers began to recognise that these 'stars' were actually one and the same. As they kept track of Venus' movements over generations and even centuries, they came to realise that Venus (like the other planets) was no star. And like the constellations of old, the planet began to give rise to its own myths and legends. 

Source: ESA

To ancient people worldwide, the planet was associated with the goddess of fertility, childbirth, love, and eroticism. When astronomy emerged as a modern science, new theories and new myths emerged. Until the 20th century, Venus' opaque cloud layer was thought to be rain clouds, which gave rise to the notion that Venus' surface was covered in oceans.

Right on up until the 1960s, there was speculation that there could be life Venus, and even a civilisation. This was dispelled when the first robotic probes were sent to Venus to gather information about its atmosphere and surface (as part of the NASA Mariner and Soviet Venera programs). Thanks to these missions, we learned the awful truth about Venus.

'Abandon all hope, ye who enter here!'

Venus is the hottest planet in the Solar System, with surface temperatures that remain steady at about 464 °C (867 °F) – that's hot enough to melt lead, by the way! The atmospheric pressure is also 92 times that of Earth, which is so dense that a person would be crushed by it! The air is a toxic plume composed predominantly of carbon dioxide (96.5%) with other trace gases.

As if that wasn't enough, clouds of sulfuric acid rain also permeate the atmosphere. So, in addition to being melted or crushed, anything on the surface of Venus has a good chance of being dissolved as well. There are no two ways about it: Venus is the closest thing in real life to Dante's Inferno!

And yet, there are a few things that make Venus appealing as another potential home for humanity. Compared to other planets, the force of gravity on the surface is 8.87 m/s², a little more than 90% (0.9 g) of what we experience here on Earth. On Mars and Mercury, the gravity is in the vicinity of 0.38 g, whereas the Moon's gravity is 0.165 g.

This would mean that the worst effects of living beyond Earth – muscle atrophy, bone density loss, diminished organ function – would not be an issue for human settlers. With a healthy exercise regimen and some minor medical intervention, life on Venus would be as close to living on Earth as is humanly possible (without fancy technological intervention).

Cities in the clouds

For example, the highly dense nature of Venus' atmosphere creates some unique opportunities for living environments. At an altitude of just above 50km above the surface, Venus' atmosphere has a pressure of approximately 100 kPa, which is slightly less than Earth's at sea level (101.325 kPa), and temperatures as low as 86 °F (30 °C).

The atmosphere above would also protect against cosmic radiation, comparable to how Earth's atmosphere shields life on the surface. For this reason, there has been speculation since the 1970s that humans could establish settlements in Venus' atmosphere, the first recorded instances coming from Soviet scientists. 

Images of Venus' surface captured by the Soviet Venera 14 probe. Source: RAS/Ted Stryk

In 2003, NASA scientist Geoffrey A Landis revitalised the idea in a paper titled 'Colonization of Venus'. At an altitude of 50km above the surface, he claimed, such cities would be safe from the harsh Venusian environment:

'[T]he atmosphere of Venus is the most earthlike environment (other than Earth itself) in the solar system. It is proposed here that in the near term, human exploration of Venus could take place from aerostat vehicles in the atmosphere, and that in the long term, permanent settlements could be made in the form of cities designed to float at about 50km altitude in the atmosphere of Venus.'

According to Landis' proposal, these aerostats would be able to remain buoyant in Venus' atmosphere, filled with nothing but breathable air (a nitrogen-oxygen mix of 79:21). In 2015, NASA began exploring the possibility as a serious mission concept for sending crewed spacecraft to Venus as part of their High Altitude Venus Operational Concept (HAVOC). 

As outlined by Dale Arney and Chris Jones (from NASA's Langley Research Center), the proposal calls for all crewed portions of the missions to be conducted using lighter-than-air flyers. These habitats could also serve as terraforming platforms, slowly converting Venus' atmosphere into something livable so the colonists could eventually migrate to the surface.

Cooling hell down

There are many ways of terraforming Venus, by which we mean altering the environment to be more like Earth. The process is straightforward enough, requiring four significant changes:

1. Cool the planet's atmosphere
2. Thin out the atmosphere
3. Convert the atmosphere to N₂/O₂
4. Reduce the planet's rotation to a 24 hour/day cycle

Luckily, each of these steps is complimentary in one way or another to the other three. Since Venus absorbs twice as much sunlight as Earth, solar radiation is believed to have played a major role in the runaway greenhouse effect that has made it what it is today. One proposed method for cooling the planet, therefore, calls for solar shades.

If it were a single lens, it could be located around the Sun-Venus L1 Lagrangian Point, limiting the amount of sunlight reaching Venus. Alternately, solar reflectors could be placed in the atmosphere to reflect solar radiation into space. These could come in the form of large reflective balloons or sheets covered with a diamond coating.

 

In his proposal, Landis suggested that his aerostats could act as solar shields and processing stations. This proposal has the advantage of using locally-sourced carbon dioxide, which would be broken down chemically to produce carbon (the basic building blocks of organic synthesis) and oxygen gas (which could be used inside the habitats). 

The shades would gradually cool the atmosphere to the point that the dense clouds of CO₂ would freeze and form dry ice. This ice could then be exported, buried, or sequestered and would have the added benefit of reducing the atmospheric pressure. Another possible method involves chemically converting the atmosphere into something that could support life.

'The Long Rain'

Carl Sagan made the first proposal for terraforming Venus in his 1961 paper, 'The Planet Venus', suggesting that genetically-engineered cyanobacteria could be introduced to the atmosphere to transform carbon dioxide into organic molecules. This idea became largely infeasible due to the discovery of the planet's sulfuric acid clouds.

This was followed by a proposal from British scientist Paul Birch, who released a study in 1991 titled 'Terraforming Venus Quickly'. Birch proposed bombarding Venus' atmosphere with a hydrogen and iron aerosol, which would chemically produce tremendous amounts of water. This would trigger 'The Long Rain' that would eventually cover 80% of the planet with oceans (perhaps for the second time).

It would also produce large amounts of graphite (crystallised carbon), which must be captured and removed. The remaining atmosphere, which Birch estimated would have a pressure of about three bars (three times that of Earth), would mainly be composed of nitrogen that could act as a buffer gas. Oxygen gas could then be imported or produced locally to make the atmosphere truly breathable.

More recently, another ambitious proposal for using hydrogen was suggested by futurist Isaac Arthur. In a video titled 'Winter on Venus', he explained how a 'hydro-cannon' could be created by focusing ionised hydrogen into a beam directed at Venus. This combination of 'star lifting' and 'stellasing' could be used to thin Venus' atmosphere and introduce hydrogen to create water.

Another method involves bombarding Venus with refined calcium and magnesium to create carbonates. This idea was proposed by Mark Bullock and David H Grinspoon (from the University of Colorado at Boulder) in a 1996 paper titled 'The stability of climate on Venus'. This could even be done by drilling into Venus' crust to access its own deposits of calcium and magnesium oxides.

These carbonates could be sequestered in the mantle, where they could someday become part of a carbon cycle (which is contingent on Venus being tectonically active). Combined with a solar shade, the chemical conversion of the atmosphere using hydrogen and iron aerosols (or both), Venus would be covered in oceans and have abundant chemical compounds left over.

 

Day and night

Another effective means of terraforming Venus involves altering its rotational speed. At present, Venus rotates once on its axis every 243 days, which is the slowest rotation period of any planet in the Solar System. As such, Venus experiences extremely long days and nights, which humans and Earth flora and fauna would have a very difficult time adapting to.

It has also been theorised that the planet's slow rotation could explain why it does not have a significant magnetic field, as Earth does. Over the years, several solutions have been suggested as to how Venus' rotational period could be sped up, or how Earth's rotation could be simulated. In his proposal paper, Birch suggested creating a system of orbital solar mirrors near the Sun-Venus L1 Lagrange Point.

These mirrors would direct sunlight towards another solar mirror in polar orbit around Venus. By ensuring different hemispheres received reflected sunlight, this system of mirrors could simulate a 24-hour day/night cycle. Other proposals have suggested speeding up Venus' rotational velocity by hitting the surface with meteors or conducting close fly-bys with massive objects.

If struck at the right angle, these impacts could have the effect of slowing and reversing Venus' rotation, theoretically eventually speeding up its orbital period to 24 hours. The benefits include the possibility that the same dynamo effect that planet Earth has in its core (which gives us our magnetic field) will also be reawakened in Venus.

This magnetic field would help ensure that Venus' fluffy new atmosphere will not be stripped away by solar wind over the course of eons. If these impactors also carried abundant amounts of calcium, magnesium, and other carbon-sequestering compounds, they would also help convert the atmosphere to something breathable.

Impactors would have the added benefit of ejecting some of Venus' current atmosphere into space. Other methods for reducing the atmosphere by exporting its gases call for space elevators and mass accelerators on floating platforms above the clouds. These could 'scoop' gas from the atmosphere over time and eject it into space. 

As you can see, the process of converting Venus into a livable environment involves steps that are complementary to each other. Whether we are thinning the atmosphere, cooling the planet, converting the atmosphere, or speeding up its rotation, progress in one area of terraforming could also have positive implications in other areas.

There seem to be many options (or combinations thereof) for accomplishing this goal, by which Venus can be transformed into a warm, oceanic, and very Earth-like environment. The people born in this paradise will be known as 'Venusians' or 'Cythereans', who will undoubtedly be known for their hospitality and relaxed nature! 

 

And in the meantime, we can establish floating cities where this work can be done, generation after generation, until the cities in the sky are ready to descend slowly to the surface. When they arrive, they are sure to find an oceanic paradise that is just waiting for life to be (carefully) introduced onto its surface.

"We thank you for spending time with us here on the high seas of Venus! We know that leaving can be hard after many days of sand, surf, and Sun. Be sure to pick up some souvenirs from our shops, including decorative motifs of all the fertility goddesses. We also have many copies of the popular myths associated with them. Be sure to sample volumes such as 'Inanna's Descent to the Netherworld,' 'The Iliad,' and 'The Legend of Sky Woman.'

"We wish you well and hope that if your final destination is not Earth, that the transition process to low-gravity will be as painless as possible. We recommend you take your time adjusting to the low-gravity environment sections aboard Pythagoras station. Feel free to spend as much time as your bookings can allow.

"When you're contemplating your next vacation destination, be sure to keep Venus in mind. Between our oceans, archipelagos, seafront properties, and temperature conditions, we are the vacation destination of the Solar System. In short, There's a reason Venus is known as 'Earth's Sister Planet.'"