Mars is a desert planet in the Milky Way, it is not seen but it is metioned through the entire series.
Mars was an ocean planet ruled by the Blisk, who were somewhat very cocky about it. The Furons deliberately assaulted Mars, reducing the planet to a dry desert. The Blisk were defeated in what was called the Martian War. All of the Blisk were destroyed except one warship, which crashed in Tunguska in the Soviet Union on the 30th of June, 1908. While here, they built a base. Mars has been a desert planet ever since the Martian War.