Why is Jupiter called a gas planet?
The inner planets (Mercury, Venus, Earth, Mars) are called terrestrial planets because they have thin atmospheres in comparison with their large rocky and icy solid interiors. In moving outward beyond Mars and the asteroid belt, we enter a region of very different planetary composition. The next four planets are considered gas giants (Jupiter, Saturn, Uranus, Neptune). The outer most layer of Jupiter is made up of gases. In fact this atmosphere is huge – a few thousand kilometers thick. This was the reason Jupiter was initially called a gas planet. At depths below this, pressures become so large, that the gases begi n to change from gaseous form to liquid form. The liquid portion of Jupiter is actually the largest section of Jupiter (it is almost 4 times the size of the gaseous atmosphere!). For this reason, some scientists have begun to ca ll Jupiter a “fluid planet” instead of a gas planet!
