Most astronomers feel that it would be impossible for life to exist on Venus. Today, Venus is a very hostile place. It is a very dry planet with no evidence of water, its surface temperature is hot enough to melt lead, and its atmosphere is so thick that the air pressure on its surface is over 90 times that on Earth.
Past habitability potential
Recent studies from September 2019 concluded that Venus may have had surface water and a habitable condition for around 3 billion years and may have been in this condition until 700 to 750 million years ago.
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.
The surface of Venus is completely inhospitable for life: barren, dry, crushed under an atmosphere about 90 times the pressure of Earth's and roasted by temperatures two times hotter than an oven.
The terraforming of Venus to support human life would require at least three major changes to the planet's atmosphere: Reducing Venus' 850°F (454,4°C, or 773°K) surface temperature. Eliminating most of the planet's dense 10 MPa (~90 atm) carbon dioxide atmosphere, via removal or conversion to some other form.
It might once have been a habitable ocean world, like Earth, but that was at least a billion years ago. A runaway greenhouse effect turned all surface water into vapor, which then leaked slowly into space.
While Venus, Earth, Mars, and even the Moon have been studied in relation to the subject, Mars is usually considered to be the most likely candidate for terraforming.
According to recent climate modelling, for much of its history Venus had surface temperatures similar to present day Earth. It likely also had oceans, rain, perhaps snow, maybe continents and plate tectonics, and even more speculatively, perhaps even surface life.
It's too dry and too acidic for microbial life to exist above the surface of the hellacious planet, according to a new study.
"If life was responsible for the sulfur dioxide levels we see on Venus, it would also break everything we know about Venus's atmospheric chemistry."
Venus would not begin to cool down until after most of the carbon dioxide had already been removed.
The surface of Venus witnessed volcanic eruptions for hundreds of years. New research has suggests that volcanoes may have played a role in destroying Venus and leaving it as an uninhabitable world.
Mercury's environment is not conducive to life as we know it. The temperatures and solar radiation that characterize this planet are most likely too extreme for organisms to adapt to.
However, this clement period was not to last, and as the eons passed Mars gradually transitioned to its present-day climate, with an atmosphere too cold and thin to support liquid water, a necessary ingredient for life, on the surface.
Early in martian history, the climate was warm enough for potentially habitable lakes and rivers of water to exist. However, roughly 3.6 billion years ago, the climate shifted from being habitable to inhabitable when liquid water disappeared from the surface.
According to recent climate modelling, for much of its history Venus had surface temperatures similar to present day Earth. It likely also had oceans, rain, perhaps snow, maybe continents and plate tectonics, and even more speculatively, perhaps even surface life.
Uranus' environment is not conducive to life as we know it. The temperatures, pressures, and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to.
Among the stunning variety of worlds in our solar system, only Earth is known to host life.
For starters, Venus' atmosphere is chock-full of greenhouse gases like carbon dioxide. These gasses are responsible for making this planet 'hellacious' to the highest regard. Our atmosphere, which is primarily responsible for distributing the energy (and heat) we receive from the sun, has the opposite effect of Venus.
Drastic climate shifts 700 million years ago made the planet's atmosphere incredibly dense and hot. The hellish planet Venus may have had a perfectly habitable environment for 2 to 3 billion years after the planet formed, suggesting life would have had ample time to emerge there, according to a new study.
However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet's early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space.
Venus' thick atmosphere traps heat creating a runaway greenhouse effect – making it the hottest planet in our solar system with surface temperatures hot enough to melt lead. The greenhouse effect makes Venus roughly 700°F (390°C) hotter than it would be without a greenhouse effect.
To break it down, only Enceladus and Titan appear to be viable candidates for terraforming. However, in both cases, the process of turning them into habitable worlds where human beings could exist without the need for pressurized structures or protective suits would be a long and costly one.
It is possible to terraform a planet without the use of life. We can produce oxygen from water or from carbon dioxide via electrolysis. Imagine this scenario: A galactic company starts the terraforming of a planet.
Terraforming of planets like Pluto is unlikely and highly expensive, but not impossible. At least in the nearest 1000 years. But, if we think further away, it can become a reality. A more advanced civilization that had overpopulated all planets in its solar system would like to terraform even a colder one.