He discovered them with a homemade telescope. Jupiter's atmosphere is made of hydrogen, helium, ammonia, and methane. The atmosphere is not very thick at all. Methane is poisonous and is explosive near oxygen. It is found in deep pits and near swampy, stagnant pools.
Ammonia is made of hydrogen and nitrogen.
Hydrogen is the most plentiful gas. It is usually blended with other gases. The surface is an ocean of liquid hydrogen which is known to be 10 thousand or more miles deep. They are 250 degrees below 0. The center of Jupiter is very hot.