Jupiter, a gas giant planet, does not have a solid surface or a distinct core like terrestrial planets such as Earth. Instead, it is primarily composed of hydrogen and helium gases, with trace amounts of other elements.
As you descend beneath Jupiter's clouds, the atmospheric pressure and temperature increase significantly. The exact transition from the gaseous outer layers to the interior is not precisely known, but it is believed that the gases gradually become denser and eventually transform into a state referred to as a "supercritical fluid," where the distinction between gas and liquid becomes less clear.
The extreme pressure and temperature conditions within Jupiter make it impossible for a human or any conventional spacecraft to survive the journey. The immense pressure would cause crushing forces that far exceed what the human body can endure, and the temperature and turbulent conditions would pose additional challenges.
Jupiter's internal structure is still not fully understood, as it is difficult to probe the planet's deep interior. Our knowledge of Jupiter's core is mostly based on theoretical models and computer simulations. It is hypothesized that at the center of Jupiter, there may be a solid core made up of heavier elements such as rock, metal, and possibly even exotic materials like hydrogen compounds under extreme pressure. However, the exact composition and nature of Jupiter's core remain uncertain and are still the subject of scientific investigation.