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.
Among the stunning variety of worlds in our solar system, only Earth is known to host life.
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.
But on Mars, carbon dioxide is 96% of the air! Meanwhile, Mars has almost no oxygen; it's only one-tenth of one percent of the air, not nearly enough for humans to survive. If you tried to breathe on the surface of Mars without a spacesuit supplying your oxygen – bad idea – you would die in an instant.
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.
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.
It is unlikely that life as we know it could survive on Mercury due to solar radiation, and extreme temperatures.
Conventional water-based biochemistry is nearly impossible in Venusian conditions. In June 2021, calculations of water activity levels in Venusian clouds based on data from space probes showed these to be two magnitudes too low at the examined places for any known extremophile bacteria to survive.
All of the planets, except for Earth, were named after Greek and Roman gods and godesses. The name Earth is an English/German name which simply means the ground. It comes from the Old English words 'eor(th)e' and 'ertha'. In German it is 'erde'.
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.
Many scientists believe that RNA, or something similar to RNA, was the first molecule on Earth to self-replicate and begin the process of evolution that led to more advanced forms of life, including human beings.
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.
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.
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.
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.
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.
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.
But temperatures at this region would be thousands of degrees; hot enough to melt rock. And the pressure from the weight of all the atmosphere would be crushing. In short, there is simply no way one could stand on the “surface of Neptune”, let alone walk around on it.
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.
Jupiter is made of mostly hydrogen and helium gas. If you tried to land on Jupiter, it would be a bad idea. You'd face extremely hot temperatures and you'd free-float in mid-Jupiter with no way of escaping.
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.
Mars' dramatic shift from a warm and wet planet to a cold and dry one may have been chiefly driven by greenhouse gases other than carbon dioxide (CO2), a new study suggested. Missions to the Red Planet have revealed the presence of riverbanks and deltas, evidence that it was once home to rivers and lakes.
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.
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.