Final answer:
The opposite of a Jovian planet is a terrestrial planet which is primarily rocky, smaller in size, and has a solid surface, unlike the gas giants.
Step-by-step explanation:
The opposite of a Jovian planet is a terrestrial planet. The four planets closest to the Sun, Mercury through Mars, are known as terrestrial planets. They are smaller than Jovian planets and are composed primarily of rock and metal, with solid surfaces that can support geological features like craters, mountains, and volcanoes. In contrast, Jovian planets like Jupiter through Neptune are gas giants, much larger and primarily made of lighter ices, liquids, and gases, with dense cores surrounded by vast layers of hydrogen and helium.