From the top: Callisto, Triton, Europa, Moon, Dione, Io.
The background shows galaxies photographed by Hubble.
Planets fall into several categories: Water/ice, sulfur, hydrocarbon, and airless.
Earth fits the water category. Mars, Europa, and Triton contain significant ice.
Sulfur dioxide replaces water in the atmospheres of Venus and Io.
Hydrocarbons dominate the atmospheres of the Titan and the large planets.
In our solar system, Mercury and the Moon are airless. Pluto is unknown.
Most of the other large moons are covered with ice and have interior oceans.
One in six stars harbor an Earth-like planet or moon.
Sirius is only nine light-years from Earth. It has no planets but it has numerous
asteroids containing metal, rock, and ice that are used to construct a habatat.
Read my novel to find out how this is accomplished.
(Warning: continuous viewing can cause eye-burn).