Spherical "Aerobots" may one day swarm the caves of Titan — a moon of Saturn that NASA says is one of the most Earthlike in our solar system.
Titan is covered in rivers, lakes and seas of hydrocarbons, like methane and ethane, as well as a strange "karst" terrain including underground sinkholes and caves. No rover could easily traverse this surface, but flying vehicles may have more success.
