AboutAlter ego: J'onn J'onzz or John Jones
Species: Green Martian
Place of origin: Mars
Team affiliations: Justice League, Outsiders, Black Lantern Corps
Notable aliases:Bloodwynd, Bronze Wraith, Fernus , Manhunter from Mars, Marco Xavier, Mrs. Klingman, William Dyer, Betty Nehring, John Johnstone, Joan Jones, Brainwave, Blockbuster, and Gypsy.
Enemies:Malefic (his brother and engineer of the Hronmeer's Curse plague), Kanto (Darkseid's personal assassin, he and J'onn clashed during the old days on Mars), The Swarm (an alien armada that J'onn will face in the centuries to come).
Abilities: Superhuman strength, speed and durability
Telepathy, Telekinesis, Invisibility, Regeneration, Longevity, shape-shifting, phase-shifting, Martian vision and Flight, Black Lantern Power Ring
The character makes his first appearance in Detective Comics #225, cover dated November 1955. This origin story sets up a number of important character points, many of which have carried onto the modern age with little or no change. In this first story, the character is pulled to earth by an experimental teleportation beam (originally presented as an attempted communication device) constructed by Dr. Erdel, the shock of the encounter kills Dr. Erdel and leaves J'onn with no method of returning home. The character decided to fight crime while waiting for Martian technology to advance to a stage that will enable his rescue. To that end, he adopts the identity of John Jones, a detective in the fictional Apex City (later retconned as Chicago).
During this period, the character and his back story differ in some minor and some significant ways from modern treatments. Firstly, as with his counterpart, the Silver age Superman, his power range is poorly defined, and his powers expand over time as the plot demands. The addition of precognitive abilities (Detective Comics #226) are quickly followed by telepathy and flight ], "Atomic vision", super-hearing and many other powers. In addition, his customary weakness to fire is only manifested when he is in his native Martian form.
A more significant difference, is that at this time, there is no suggestion that Mars is a dead planet or that the character is the last of his kind. Many of the tales of the time feature either Martian technology or the appearance of other Martian characters, Detective Comics #236 (October 1956), for example, features the character making contact with the planet Mars and his parents.
J'onn eventually reveals his existence to the world, after which he operates openly as a superhero and becomes a charter member of the Justice League. He abandons the detective John Jones identity when Jones is ostensibly killed in action. J'onn spent the next several years involved in mystical adventures involving the Idol Head of Diabolu, an artifact which generates supernatural monsters. He later takes the persona of Marco Xavier in order to infiltrate the international crime cartel known as VULTURE.
His appearances with the League kept him in the public eye long after his own series were canceled. He is a founding member of the team, and served as a member during many of its various incarnations. From the late 1960s until the late 1970s, J'onn was absent from the JLA, having left Earth to find and become leader of New Mars. This time period is later retconned during the Crisis on Infinite Earths, and his period of absence is never again referenced.