Radioactivity - you probably didn't think that was good for life or that it helped to create life. But, planet radioactivity can be a good thing. The perfect balance (what a coincidence) of radioactive elements inside planets like ours might make it habitable. Researchers are thinking about how Mars is losing its important water.
Almost all water on Mars today exists as so-called ice, though it also exists in small quantities as vapor in the atmosphere. What was thought to be low-volume liquid brines in shallow Martian soil, also called recurrent slope lineae, may be grains of flowing sand and dust slipping downhill to make dark streaks.
The "ice giant" (also called "water giant") planets Uranus and Neptune are thought to have a supercritical water ocean beneath their clouds, which accounts for about two-thirds of their total mass, most likely surrounding small rocky cores.
Earth seems to be the only known planet to have bodies of liquid water on its surface. Europa is thought to have subsurface liquid water.
Slightly smaller than Earth's Moon, Europa is primarily made of a certain silicate rock and has a water-ice crust and probably an iron-nickel core. It has a very thin atmosphere, composed primarily of oxygen. Europa is the smallest of the four Galilean moons orbiting Jupiter.
There is certain radiation inside the planet that is protecting us from radiation outside.
In addition to their own resiliency, living things and the cells they are made of are protected from excessive amounts of UV radiation by a chemical called ozone. A layer of ozone in the upper atmosphere absorbs UV radiation and prevents most of it from reaching the Earth.
Saturn's largest moon, Titan, is an icy world whose surface is really completely obscured by a golden hazy atmosphere. Titan is the only solar system object other than Earth boasting stable liquids on the surface, with lakes and seas of full of methane being major features at its polar regions. Hilly and mountainous areas, thought to represent exposed portions of Titan's crust of water ice, represent 14% of the surface. Also, damaging particles cannot really make it to Titan's surface; they're absorbed by the atmosphere, meaning that it's a "safe environment" for humans to live in.