The Solar System

The Solar System is a star system in the Milky Way Galaxy where most of the events in the Invader Zim series takes place.

Mercury[]

Mercury is the planet closest to the sun. Due to its location, it is completely lifeless. However, at some distant point in the past, the Martians converted it into a spaceship as a test run for doing the same to their own planet.

In the episode "Battle of the Planets", Dib discovers this with help from Agent Darkbootie and travels to Mercury, piloting it against Zim, who is trying to use Mars to crush all life on Earth. After succeeding in this, Dib presumably returned Mercury to its normal place.

Earth[]

Earth is the third planet from the sun, the homeworld of the human race, and the planet where the majority of events in the series take place; in fact it's the only planet to appear in every episode of the series.

It is also the only planet in the system that is currently known to support life. It has one natural satellite, The Moon, which has a few prominent mentions or appearances in various TV episodes and comic issues.

Mars[]

Mars is the fourth planet from the sun. It is barren and currently lifeless, but it used to be inhabited by a native race, until they worked themselves to death turning their planet into a giant spaceship "because it was cool".

Its primary appearance is in the episode "Battle of the Planets", where Zim discovers its nature as a ship that was made by the now extinct Martians and tries to use it to destroy Earth; when this plan fails, Mars is sent spinning off into deep space, where it destroys part of the Irken Armada by slamming into it.

Saturn[]

Saturn is the sixth planet from the sun, a gas giant that is the second largest planet in the Solar System, famous for its prominent rings. It briefly appears in "Battle of the Planets", when Zim and Dib race Mars and Mercury through its rings as part of the titular battle, and again in "The Frycook What Came from All That Space" as Zim passes it while flying back to Earth following his escape from Sizz-Lorr on Foodcourtia.

According to a rumored loose plot outline for the series finale, Saturn is where Dib and The Resisty would have been exiled to after failing to conquer or destroy the Irken Empire.

Other Planets[]

There are several other planets in the Solar System that have yet to make any appearances in either the series or comics: Venus lies between Mercury and Earth, Jupiter lies between Mars and Saturn, and beyond Saturn are Uranus, Neptune, and Pluto (though the last is no longer considered a planet in real life).

Asteroid Belt[]

The asteroid belt is the circumstellar disc in the Solar System located between the orbits of the planets Mars and Jupiter. It only makes two important appearances in the show.

First, when Zim idiotically drove Mars through the asteroid belt in an attempt to outwit Dib but only ended up with several asteroids crashing into the planet, causing Zim to make a hasty retreat in his Voot Runner.

The second time was in "Backseat Drivers from Beyond the Stars", when Zim and Dib were driving the Massive and, more often than not, they kept crashing it into oncoming asteroids.

Facts of Doom[]

Humans named every planet in the Solar System and technically speaking they can claim ownership of them, even if they have yet to actually set foot on any of them.
Aside from humans, the Irkens and the Martians are the only known species to have sent probes to explore the planets in the Solar System.
If Zim ever conquers the Earth, it's conceivable to think that the Irken Empire would also claim ownership of the Solar System and would give each planet any purpose they see fit.