Compare the geology of Callisto, Ganymede, and Titan.

Explanation: Ganymede, Callisto, Titan are the moons of outer planets or gaseous planets which are made up of ice and rock. Callisto is an ice-covered moon and has no inner or outer activity and is considered basically geologically dead. Ganymede has rocky core and shows signs of tectonic activity, including long cracks in the crust and regions of young surface terrain. Titan has active geology of liquid hydrocarbons on the surface, rain back onto the surface and evaporation into the atmosphere. It has similar size, composition and mass to Ganymede and Callisto.