Besides Earth, Mars would be the easiest planet to live on. Mars has liquid water, a habitable temperature and a bit of an atmosphere that can help protect humans from cosmic and solar radiation. The gravity of Mars is 38% that of the Earth.
Among the stunning variety of worlds in our solar system, only Earth is known to host life.
To conclude, any new human colonisation on another planet would be very difficult. The extreme weather conditions, the chemistry of the atmosphere and the vast amounts of resources needed to support human life all play into this.
It could be possible for humans to walk on 3 planets of the Solar system besides Earth: Mercury, Venus, and Mars. These are rocky planets with solid surfaces unlike the outer planets like Jupiter, Saturn, Neptune, and Uranus that are mostly made out of gas.
Jupiter's environment is probably 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.
Three (Venus, Earth, and Mars) out of eight planets might be able to support life. Based on recent discoveries of planets outside of our Solar System, it was estimated that 1 in 5 planets could exist in the habitable zone of their star: Average lifetime of a planet.
Despite its smaller size, the planet's land area is also roughly equivalent to the surface area of Earth's continents—meaning that, at least in theory, Mars has the same amount of habitable real estate. Unfortunately, the planet is now wrapped in a thin carbon dioxide atmosphere and cannot support earthly life-forms.
It is unlikely that life as we know it could survive on Mercury due to solar radiation, and extreme temperatures.
The air on mars is thinner than that on Earth. On Earth, 21 percent of the air is oxygen, which is what makes it the ideal place for human life. But on Mars, oxygen makes up 0.13 percent of the air. The majority is carbon dioxide, which is harmful to humans.
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.
Although you might think it would be cool, humans could not live on the moon! (Maybe one day in the future…) The moon has almost no atmosphere, so there's no air for us to breathe. There is no water on the moon either, and we need to drink water to survive.
Mars does have an atmosphere, but it is about 100 times thinner than Earth's atmosphere and it has very little oxygen. The atmosphere on Mars is made up of mainly carbon dioxide. An astronaut on Mars would not be able to breathe the Martian air and would need a spacesuit with oxygen to work outdoors.
Potential for Life
The surface of Pluto is extremely cold, so it seems unlikely that life could exist there. At such cold temperatures, water, which is vital for life as we know it, is essentially rock-like. Pluto's interior is warmer, however, and some think there could even be an ocean deep inside.
Potential for 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.
Habitability. Robert Zubrin has pointed out that Titan possesses an abundance of all the elements necessary to support life, saying "In certain ways, Titan is the most hospitable extraterrestrial world within our solar system for human colonization." The atmosphere contains plentiful nitrogen and methane.
Uranus is a ball of ice and gas, so you can't really say that it has a surface. If you tried to land a spacecraft on Uranus, it would just sink down through the upper atmosphere of hydrogen and helium, and into the liquid icy center.
The atmosphere of Venus is very hot and thick. You would not survive a visit to the surface of the planet - you couldn't breathe the air, you would be crushed by the enormous weight of the atmosphere, and you would burn up in surface temperatures high enough to melt lead.
As a gas giant, Saturn doesn't have a true surface. The planet is mostly swirling gases and liquids deeper down. While a spacecraft would have nowhere to land on Saturn, it wouldn't be able to fly through unscathed either.
Evidence points to oceans on other planets and moons, even within our own solar system. But Earth is the only known planet (or moon) to have consistent, stable bodies of liquid water on its surface.
Jupiter: Being a gaseous planet, Jupiter would make for a uniquely uncomfortable life. On — or in? — this enormous planet, "you would descend forever into the gaseous atmosphere until you're crushed by the pressure of the planet's layers."
Mariner 4, which flew by Mars on July 14, 1965, found that Mars has an atmospheric pressure of only 1 to 2 percent of the Earth's. Temperatures on Mars average about -81 degrees F. However, temperatures range from around -220 degrees F. in the wintertime at the poles, to +70 degrees F.
Yet Earth remains a standout, and so far, one of a kind. Of the thousands of exoplanets – planets around other stars – confirmed by our increasingly powerful telescopes, and despite extensive probing of the solar system, ours is still the only planet known to host life.
There is only one planet where gaseous oxygen is found: Earth! And the only reason that Earth has oxygen is because Earth has plants that do photosynthesis. There is no other natural process that we know of that will put significant amounts of oxygen into a planet's atmosphere.
It's relatively cool with an average annual temperature of -60 degrees Celsius, but Mars lacks an Earth-like atmospheric pressure. Upon stepping on Mars' surface, you could probably survive for around two minutes before your organs ruptured.
The Sun could not harbor life as we know it because of its extreme temperatures and radiation. Yet life on Earth is only possible because of the Sun's light and energy.