Jupiter has no true solid surface. It is a gas giant made mostly of hydrogen and helium, and what we see are the tops of its clouds, arranged in dark belts and bright zones by strong jet streams. Winds near the equator reach about 335 mph (539 km/h), and storms such as the Great Red Spot, an oval twice as wide as Earth, have lasted for centuries because there is no solid ground to slow them.
Below the clouds, rising pressure and temperature squeeze hydrogen gas into a liquid and, deeper still, into electrically conducting metallic hydrogen. NASA’s Juno mission found that the core is not a small solid ball but a large, partly dissolved “fuzzy” core. A spacecraft would have nowhere to land; it would be crushed, melted, and vaporized as it descended.
Source: NASA Science: Jupiter Facts
Image: Jupiter by Cassini, NASA/JPL/University of Arizona, public domain, via Wikimedia Commons.