Where does all the helium & hydrogen on jupiter come from?
Hydrogen and helium are by far the most abundant two elements in the universe, so we expect them to be a major component of stars and of large planets that have the gravity to retain these two light gases. Hydrogen and helium were both created in the big bang, and additional helium is formed by nuclear fusion reactions in stars. These gases are rare in Earth’s atmosphere because our gravity is too weak to hold them for long.
