Mars is the fourth planet in the Sol System.
It is unknown if the Neutropians originate on Mars or if they settled on the planet.
- The suggestion that Sparky lives on Mars was suggested by him being refered to on a few occasions as a Martian and in the episode "The No-L 9" Sparky and Zulia can view Earth in the sky over their home. This would be somewhat inaccurate as Earth can not be easily viewed from Mars orbit. The view of Earth shown in that episode would be more appropriate to being on Luna (Earth's moon).