Mars is a planet in the Solar System.
In the 1987 TV series episode The Fifth Turtle, Mars is one of the celestial bodies in the conjunction where Krang uses Capsidium crystals to re-power the Technodrome.
In the TMNT Adventures story The Wrath of the Fire God, the astronomers observe the planet in the beginning of the story, refering to 19th century-early 20th century beliefs about canals on Mars.
In the 2012 TV series episode Earth's Last Stand, the Triceratons fly past it on their way to Earth.
Dumpjumper also comes from Mars.