Worlds of the Solar System

The Red Planet. Mars has held our curiosity as a species for a very long time. Percival Lowell's 1895 book on Mars, where he proposed canals were being used by intelligent aliens to move water on a drying world, led directly to H.G. Wells' "War of the Worlds" and the beginning of alien scifi. Now we want to know more about the 4th rock from the Sun. What was Mars like in the distant past? How has Mars changed over time? Was there ever life, or is there still life, on the Red Planet? Will humans one day populate the surface of Mars?

Many of the moons of our solar system are icy bodies, and, among them, there are several that have been shown to likely contain subsurface oceans. Though Earth itself is an ocean world, this section is primarily for considering icy moons (including those with oceans). However, there will be comparisons to Earth and other potential worlds with surface oceans.