Solar energy from the yellow sun is the source of energy for Kryptonian powers. When Superman is exposed to large amounts of sunlight, his powers can be greatly magnified. If a Kryptonian is powerless, absorbing a large amount of sunlight radiation can regenerate their powers. Close exposure to the sun causes Martians to lose their powers. It is unknown whether it is permanent or just temporary, or whether it was the sun's radiation or simply the flames generated by the sun - an extension of their weakness.