Martian Manhunter

On Mars, when a racial war broke out between the green-skinned Martians and the white-skinned ones, J'onn J'onzz, a leading citizen on his native world was placed in charge of the army. Having been defeated by the white Martians leader, Benn Blanx, J'onn was banished to a desert for thirteen years. During the first year, on the planet Earth, a would-be scientist named Dr. Mark Erdel built a transmitter machine. Seeking to make contact with extraterrestrial life, he aimed his device towards the vicinity of Mars and activated it. The transmitter beam streaked across both space and time, and it brought J'onn back to Erdel's Colorado laboratory. When J'onn shapeshifted into a human-like form, Erdel was shocked and suffered a heart attack that killed him. As he was dying, Erdel asked J'onn for forgiveness for making him a prisoner of Earth.

J'onn was able to use his powers to fit into human society. He adopted a human appearance and called himself "John Jones." He became a police detective in the city of Middleton. For a long time, he worked as a policeman while secretly using his alien powers to solve cases and help people.

Some time later, the existence of the Martian Manhunter was accidentally revealed. From this point on, J'onn stopped hiding his superhero feats from the world, but he kept his double-identity as John Jones secret. It was at this time that he began to publicly appear in his green-skinned humanoid form.

He subsequently acquired policewoman Diane Meade as his partner, and an pet Zook who helped him solve cases.

In February, 1959, a panic is generated by the revelation of the presence of Martians (specifically from J'onzz and his enemy Commander Blanx and his followers) on Earth. Unable to cope with the situation alone, the Flash, summoned more experienced heroes, who would be an embryo of the Justice League. One year later, J'onn J'onzz was one of the founding members of the (official) Justice League of America.

J'onn's career as a police detective was ended by the Idol Head of Diabolu. This evil statue expelled a deadly cloud. John Jones saved a child from the cloud, but in doing so he was engulfed by it. His fellow policemen believed he must have died. J'onn took this as an opportunity to abandon his double life. He allowed the police department (even Diane Meade) to believe he had died, and as the Martian Manhunter he even attended his own funeral.

After this, J'onn J'onzz and Zook began a quest to combat the Idol Head of Diabolu, which they finally managed to destroy.

J'onn then briefly assumed the alias "Marco Xavier" in order to infiltrate the international crime cartel known as VULTURE.

J'onn served as a regular member of the Justice League of America. However, when a group of evil Martians led by General Blanx destroyed the surface of Mars, forcing all the good Martians to flee in a rocket, J'onn accompanied them into space in order to colonize a new world, leaving the Justice League. This new world, known as New Mars or Mars II, is the fourth planet from the sun of the star-system Cygnus.

Over the next few years J'onn was rarely seen, but he occasionally showed up to help the JLA. Eventually he returned to the JLA full-time. When his own people tried to invade the Earth, J'onn rebelled against them and prefered to remain with the Justice League on Earth.

When the original Justice League of America disbanded, J'onn became a member of the new "Justice League Detroit".

After the Crisis on Infinite Earths, several important details about the history of J'onn J'onzz were changed, retroactively altering the course that his career had taken up until that point.