About Jupiter

Jupiter, the largest planet in our Solar System, is a gas giant located fifth from the Sun. As reported by NASA, this celestial behemoth is so massive that it could fit over 1,300 Earths inside its volume, with a composition primarily of hydrogen and helium resembling that of the Sun itself.

Jupiter's Composition and Size

Composed primarily of hydrogen (90%) and helium (10%), this gas giant's structure includes a possible rocky core surrounded by layers of metallic hydrogen, liquid hydrogen, and a gaseous outer atmosphere [1] [2]. Its immense size is staggering, with a diameter of 142,984 km (11 times that of Earth) and a mass 318 times greater than our planet [3] [4]. The rapid rotation of this celestial behemoth, completing a full turn in just under 10 hours, results in an oblate spheroid shape with a noticeable equatorial bulge. Despite its enormous volume, Jupiter's average density is only 1.326 kg/m³, about 0.24 times that of Earth, due to its predominantly gaseous composition [4].

Great Red Spot and Atmosphere

Jupiter's atmosphere is characterized by its distinctive bands of clouds and turbulent storms, the most famous of which is the Great Red Spot. This massive anticyclonic storm, located in Jupiter's southern hemisphere, is large enough to engulf Earth twice over [1] [2]. The Great Red Spot has been raging for at least 350 years, with observations dating back to 1665 [3]. Despite its longevity, recent Hubble Space Telescope observations have revealed that the Great Red Spot is shrinking.

The planet's atmosphere is composed primarily of hydrogen (approximately 90%) and helium (10%), with trace amounts of other gases such as methane, ammonia, and water vapor [4]. This composition is similar to that of the Sun, reflecting Jupiter's origin from the same primordial material. The atmosphere is divided into latitudinal bands, with light-colored zones and darker belts that often interact turbulently at their boundaries. Jupiter's rapid rotation, completing one turn in just under 10 hours, contributes to the formation of these atmospheric bands and drives powerful winds. Wind speeds in the upper atmosphere can reach up to 620 km/h (385 mph) [4].

The colorful appearance of Jupiter's clouds is due to various chemical compounds. The reddish color of the Great Red Spot and other features is believed to be caused by complex organic molecules, sulfur, and phosphorus compounds, which are formed when ultraviolet light from the Sun interacts with chemicals in Jupiter's atmosphere [2]. Jupiter's atmosphere also exhibits remarkable phenomena such as powerful lightning storms and aurora displays. The Hubble Space Telescope has observed unprecedented detail in Jupiter's auroras, which are similar to those on Earth but nearly 1,000 times more energetic and visible only in ultraviolet light.

The atmospheric pressure and temperature increase dramatically with depth. At the arbitrary "surface" level where the atmospheric pressure equals that of Earth at sea level, the temperature is approximately -110°C. However, as one descends into the planet's interior, the pressure becomes so intense that hydrogen transitions into a liquid state and eventually into metallic hydrogen [5] [6]. Jupiter's atmosphere plays a crucial role in the planet's energy balance. Unlike Earth, Jupiter emits more energy than it receives from the Sun, indicating the presence of an internal heat source. This excess heat is believed to be a remnant of the planet's formation and is driven by the Kelvin-Helmholtz mechanism, where Jupiter slowly contracts and converts gravitational potential energy into thermal energy [1].

Galilean Moons and Rings

Jupiter's system of moons and rings is one of the most complex in our Solar System. The planet is surrounded by 92 known moons, with the four largest, known as the Galilean moons, being of particular interest to scientists.

Feature	Description
Number of moons	92 known [4] [5]
Largest moons	Io, Europa, Ganymede, Callisto (Galilean moons) [1] [4]
Largest moon	Ganymede (larger than Mercury) [1] [4]
Ring system	Faint, four-part system of dusty rings [5]
Ring composition	Material from small moons Amalthea, Thebe, Metis, and Adrastea [5]

The Galilean moons, discovered by Galileo Galilei in 1610, played a crucial role in our understanding of the universe by providing evidence that not all celestial bodies orbit Earth. Ganymede, the largest moon, is unique as it's the only moon in the Solar System with its own magnetic field [6]. Jupiter's ring system, while less prominent than Saturn's, consists of a main ring, a halo, and two gossamer rings. These structures are believed to be replenished by material from nearby small moons, a phenomenon that will be further explored by ESA's Juice mission.

Jupiter Exploration Missions

Exploration of this gas giant began in the 1970s with NASA's Pioneer and Voyager programs, followed by the Galileo orbiter which provided extensive data from 1995 to 2003 [1]. Currently, NASA's Juno spacecraft, launched in 2011 and in orbit since 2016, continues to study Jupiter's composition, gravity field, and magnetic field [5]. Future missions include ESA's Jupiter Icy Moons Explorer (Juice), set to arrive in 2031, and NASA's Europa Clipper in 2030, both focusing on the planet's potentially habitable moons. These missions aim to unravel mysteries such as the depth and composition of the moons' subsurface oceans, the uniqueness of Ganymede's magnetic field, and the potential for past or present life in the Jovian system [5].