This is an image of Jupiter.
Click on image for full size
Courtesy of NASA
The giant planets have definitely changed since their formation. But how much remains to be seen.
Most of the original air of the giant planets remains in place. (The earth-like planets lost most of their atmospheres very soon after they formed because the atmosphere drifted away).
Jupiter is made primarily of the basic materials hydrogen and helium, which is what existed near Jupiter when it was forming.
This is page 30 of 60
Shop Windows to the Universe Science Store!
Our online store
on science education, classroom activities in The Earth Scientist
specimens, and educational games