Exobiology is the portion of astrobiology that focuses solely upon extraterrestrial life.
Colonization of the planet Venus will require Venus to either be terraformed (as illustrated in this NASA depiction), or colonized via the use of floating habitats. To colonize planet Venus, humankind must develop technology to construct and occupy floating cities many kilometers above the surface of Venus.
Fortunately for those who seek to #colonizeVenus the most Earthlike extraterrestrial conditions anywhere in the solar system are to be found in the upper reaches of the Venusian atmoshere. At an elevation of roughly fifty kilometers above the surface of planet Venus, the ambient air temperature is in the 70s F, gravity is very similar to that on Earth, the ambient air pressure is similar to the surface of the Earth, and sunlight is abundant. The Venusian air is not breathable, though, since it consists primarily of CO2 with very little O2. Given all these considertions, scientists have proposed creating floating outposts at the cloudtops of Venus, to be followed by floating cities.
Incredibly, this can readily be accomplished simply by filling the floating cities with plenty of breathable air (oxygen and nitrogen) which will be much less dense than the atmosphere of Venus, and will act as a source of bouyancy sufficient to allow an outpost or city to comfortably float above the surface of Venus. A detailed proposal by NASA on the settling of planet Venus in such a manner was published in 2003 titled "Colonization of Venus".
Floating Cities of Venus
The paper specifically conjectures the settling of planet Venus via means of floating cities at about 50 km in the Venusian sky. It states that at that altitude, the Venusian atmosphere will allow a large heavy structure such as a city to float on it, like a boat on the ocean, and that the remainig atmosphere above the floating city is sufficient to shield the floating city from harmful intergalactic and solar particle event radiation. A further major benefit cited in the article is that the gravitational pull experienced by the colonists of the floating city will be nearly that of Earth, obviating the significant drawbacks of microgravity that will be experienced on the Moon or the planet Mars.
How do the cities float within the high cloud banks of planet Venus? It is possible due to the incredible coincidence that the air we need to breathe, a mixture of oxygen and nitrogen, is lighter than is the carbon dioxide laden atmoshere of Venus. Just as hydrogen or helium act as lifting gases for balloons in the atmosphere of Earth, oxygen acts as a bouyant gas on planet Venus.
The first colonists will likely use large aerostats as their bases of exploration. With these aerostats, the colonists will have platforms high above the surface of planet Venus from which to construct larger floating structures, then permanent settlements, and eventually entire cities. Much of the structural elements of these large floating strucures can be manufactured from the carbon in the atmosphere of Venus by converting gaseous carbon dioxide (CO2) into carbon and oxygen. The carbon can be made into many kinds of products including structural fibers and mats.
Life Above the Clouds
Enjoying an equable temperature, ample filtered sunlight, and the welcome tug of gravity reminiscent of home, colonists will live a surprisingly comfortable life. The floating colonists will engage in the study of their host planet, seraching for microbial life, perhaps following the trail of the sources of phosphine gas. They will be engaged in producing carbon-fiber and other materials from the abundant carbon dioxide in the air around them. A beneficial by-product of converting CO2 into carbon filaments is breathable oxygen which can be added directly into their living environment. The presence of abundant oxygen in the atmosphere of Venus in the form of CO2 makes Venus a uniquely suitable place for human colonization.
Risks to Colonists
What will happen if the outer shell of their aerostats or floating cities are ripped, punctured or torn? Because the interior and exterior air pressures will be nearly the same, there will be no rapid decompression and loss of internal air. When colonists work on the outside of their floating man-made environments, they will need oxygen to breath, and perhaps some degree of protection from droplets of weak sulfuric acid in the Venusian air, but the temperature and air pressure outside in the air of Venus will be otherwise quite tolerable.
The hyper-abundance of CO2 in the atmosphere of Venus leads us to consider the benefits and detriments of this gas. CO2 is essential for plant life on Earth, because plants "inhale" the gas for use in their growth processes, and then "exhale" oxygen after the plants have utilized the carbon in CO2 gas. CO2 is therefore essential not only for Earthly plant life but also for animal life. The presence of huge amounts of CO2 in the Venusian atmoshphere is both a blessing and a curse to the second planet from the Sun.
Living Above Venus
What will the Venusian colonists do long-term, after they have completed building their habitations and carbon fiber factories? One of the activities is going to be to discover the secrets of the planet known that Earth's twin. How did it form, was life present in the past, is the planet or it's atmosphere harboring any kind of life now?
Another major topic of endeavor will be the possible terraforming of the planet. IN order to make it more like the Earth, and habitable for humans at it's surface, Venus must first be understood. Is the carbondioxide in the atmosphere continuing to build? If so, why and to what extent?
A major ongoing source of new carbondioxide being infused into the Venusian atmosphere may be from Volcanism. Active volcanism is now suspected. The March 15 2023 edition of Science Daily reported that:
"Venus appears to have volcanic activity, according to a new research paper that offers strong evidence to answer the lingering question about whether Earth's sister planet currently has eruptions and lava flows."
This intriguing report points to a major issue in the potential terraforming of planet Venus. How do we deal with continued volcanism that
continually spews more CO2 into the atmosphere?
Interplanetary "Rest Stops"
We may chose to construct deep space interplanetary living environments between the orbits of Earth and Venus to allow "rest stop" accommodations for travelers and colonists. A Kalpana One space settlement might be suitable for this task.
Interesting articles are being written about the prospects of colonizing planet Venus.