Europa’s surface is blasted by radiation from Jupiter. That’s a bad thing for life on the surface – it couldn’t survive. But the radiation may create fuel for life in an ocean below the surface. The radiation splits apart water molecules (H2O, made of oxygen and hydrogen) in Europa’s extremely tenuous atmosphere.

To date, no definitive proof has been found of past or present life on Venus. With extreme surface temperatures reaching nearly 735 K (462 °C; 863 °F) and an atmospheric pressure 90 times that of Earth, the conditions on Venus make water-based life as we know it unlikely on the surface of the planet.

Europa has a thin oxygen atmosphere, but it is far too tenuous for humans to breathe. From the surface of Europa, Jupiter appears 24 times larger than the moon appears in our sky. Europa’s magnetic field shields its surface from Jupiter’s deadly radiation.

The best places to look for life are where the ocean overlies warm rock. This may be the case inside Europa (Jupiter) and Enceladus (Saturn), but chemical reactions with the rock would make the liquid water salty, so not good to drink.

A new study shown by NASA scientists at the Goldschmidt conference this week provides further evidence that Europa’s ocean is habitable and similar to Earth’s oceans. Europa has many cracks in its otherwise smooth surface.

Europa does have an atmosphere, although tenuous. This atmosphere is composed solely of oxygen. Unlike our atmosphere, the oxygen in Europa’s atmosphere is likely not produced biologically. Europa’s atmosphere is maintained by charged particles that hit its cold surface and produce water vapor.

On Europa, temperatures range from as high as about 140 Kelvin (about -210 degrees Fahrenheit) in dark material at the moon’s equator to as low as about 50 Kelvin (-370 degrees Fahrenheit) in bright icy patches at the moon’s poles.

If life is found to exist on Europa, the difference in the environments of Earth and Europa would likely mean terraforming would have adverse effects on the natural inhabitants of the moon.

The surface of Titan is one of the most Earthlike places in the solar system, albeit at vastly colder temperatures and with different chemistry. Here it is so cold (-290 degrees Fahrenheit or -179 degrees Celsius) that water ice plays the role of rock.

A new model from NASA scientists supports the theory that the interior ocean in Jupiter’s moon Europa would be able to sustain life.

In the Solar System’s habitable zone, there are only three natural satellites—the Moon, and Mars’s moons Phobos and Deimos (although some estimates show Mars and its moons to be slightly outside the habitable zone) —none of which sustain an atmosphere or water in liquid form.

Out of all the planets in our solar system, only Earth is know to sustain life. However, after scientists have analyzed others, some are showing the potential to sustain life, but perhaps in a way we have not seen before. The most likely planets to sustain life include Mars, Europa, Enceladus and Titan.

Callisto has a very thin atmosphere, is thought to contain an ocean, and is therefore another possible contender for life beyond Earth. However, its distance from Jupiter means it doesn’t experience such a strong gravitational pull, so it’s not as geologically active as the other Galilean moons of Io and Europa.

To date, no proof of past or present life has been found on Mars. Cumulative evidence suggests that during the ancient Noachian time period, the surface environment of Mars had liquid water and may have been habitable for microorganisms.

Eris

Uranus

Orbit and Rotation Uranus is the only planet whose equator is nearly at a right angle to its orbit, with a tilt of 97.77 degrees—possibly the result of a collision with an Earth-sized object long ago. This unique tilt causes the most extreme seasons in the solar system.

Venus

KELT-9b

Richard Gott has estimated that the human race could survive for another 7.8 million years, but it is not likely to ever colonize other planets. However, he expressed a hope to be proven wrong, because “colonizing other worlds is our best chance to hedge our bets and improve the survival prospects of our species”.