Jor-El explicitly links strength and senses to radiation, but because he mentions weaker gravity and Earth’s nourishing atmosphere [FN1], there is the misconception that Superman is powered by weaker gravity or Earth’s atmosphere. This is clearly not the case.
Superman’s powers are not dependent on gravity. Superman’s exhibits his powers under the weaker gravity of space and under the stronger gravity of the World Engine’s beam. Superman’s powers are not dependent on Earth’s atmosphere. He exhibits powers in a noxious oil rig fire with atmospherics low on oxygen. His powers allow him to survive an entire dream sequence underwater in the frigid ocean. He demonstrates, flight, strength, and durability in his multiple trips to the vacuum of space. Superman is not holding his breath. His mouth is open before he rescues Lois from the damaged escape pod. He and Zod vocalize during the satellite fight and on their return back to Earth. Even Jax-Ur explicitly ties Kal-El’s strength to radiation.
So why the confusion? read more