No, it is not possible to reduce all matter into hydrogen or helium atoms through the process of fission alone. Fission refers specifically to the splitting of atomic nuclei, typically heavier elements such as uranium or plutonium, into smaller fragments. This process releases a significant amount of energy and often produces a variety of lighter elements, including hydrogen and helium, along with other radioactive isotopes.
However, fission alone cannot reduce all matter into hydrogen or helium atoms because not all elements can be directly produced through fission. Elements beyond hydrogen and helium are created through processes like stellar nucleosynthesis, where nuclear reactions in stars generate heavier elements through fusion reactions. These elements are then dispersed through various cosmic processes, such as supernova explosions, and become part of the interstellar medium.
To create hydrogen and helium from other elements, a different process called nuclear fusion is required. Nuclear fusion involves combining lighter elements, typically hydrogen isotopes like deuterium and tritium, to form heavier elements like helium. Fusion reactions release a tremendous amount of energy, as seen in stars like the Sun. Achieving controlled nuclear fusion on Earth is a significant scientific and engineering challenge, and while progress has been made, it has not yet been fully realized as a viable energy source.
In summary, while fission can split heavy atoms into lighter elements, it cannot reduce all matter exclusively into hydrogen or helium. Nuclear fusion is the process that can potentially combine lighter elements to form helium and beyond, but its practical implementation remains a complex endeavor.