Jupiter ♃

Jupiter's atmosphere is primarily hydrogen (about 90 percent) and helium (about 10 percent), with traces of methane, ammonia, and water vapor. The planet has no solid surface; its gaseous atmosphere gradually transitions into a liquid hydrogen ocean and then a metallic hydrogen layer at extreme pressures deep within the interior. The Great Red Spot is a massive anticyclonic storm larger than Earth that has persisted for at least 350 years.

Jupiter is the largest planet in the solar system, with a diameter 11 times that of Earth and a mass 318 times greater. It rotates faster than any other planet, completing one rotation in just under 10 hours. This rapid spin creates prominent cloud bands and intense jet streams. Jupiter has a powerful magnetosphere, the largest structure in the solar system after the heliosphere, and emits more energy than it receives from the Sun.

Pioneer 10 became the first spacecraft to cross the asteroid belt and fly by Jupiter in 1973. The Galileo orbiter and probe (1995-2003) provided the first direct measurements of Jupiter's atmosphere and discovered evidence of subsurface oceans on the moons Europa, Ganymede, and Callisto. NASA's Juno mission (2016-present) orbits Jupiter's poles, studying its magnetic field, interior structure, and atmospheric dynamics. The Europa Clipper, launched in 2024, will investigate Europa's habitability.