Relative size isn't the only thing setting Earth and Jupiter apart. Compositionally, the two worlds are totally different. Mercury, Venus, Earth and Mars are all classified as terrestrial planets, meaning that they have hard outer surfaces and mostly consist of metals or silicate rocks.
On the other hand, Jupiter is the quintessential gas giant. Such planets lack outer crusts and as the name would suggest, they're overwhelmingly composed of gasses. For its part, Jupiter's two major ingredients are hydrogen and helium, though smaller quantities of methane, ammonia and water have also been detected.
Since it doesn't have a hard crust, scientists define Jupiter's "surface" as the outer level at which its atmospheric pressure equals that of Earth. Far below this external area, there's a layer dominated by molecular hydrogen. Beneath that, you'll find a level whose primary component is liquid metallic hydrogen. (A material reminiscent of the liquid mercury we find on our own planet.)
The core at Jupiter's very center inspires much debate. Some astronomers have argued that it doesn't even exist and may have long since disappeared. Data collected by NASA's Juno spacecraft tells us the core is probably real, but we still don't know what it's made of. However, the thing does appear to be less condensed than planet Earth's iron and nickel-based inner core.
OK, so what's the deal with Jupiter's so-called surface? Well, if you look at the planet through a good telescope, you'll notice alternating bands of color that run horizontally across it.
Amazingly, neighboring bands move in opposite directions. Astronomers call the darker ones "belts" while their lighter counterparts have been dubbed "zones." Variations in chemistry, transparency and/or temperature might explain the observed color differences between them. Zones and belts constantly change shape because these colorful lines are really ammonia clouds in Jupiter's atmosphere.