Over the course of the 1940s and 1950s, various alterations and additions to the makeup of Krypton were made in the comics. Among them was an explanation of why the natives of Krypton perished if they had possessed superpowers on their native world (as was the case in the earliest versions of Krypton outlined above, although this only became a problem once Superman — and by extension anyone from Krypton — was portrayed as increasingly powerful, able to withstand nuclear explosions, contrasted with his original power level in which a bursting mortar shell could penetrate his skin).