Jupiter

Overview

Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth the mass of the Sun.

Jupiter is primarily composed of hydrogen, but helium constitutes one-quarter of its mass and one-tenth of its volume. It has a rocky core of heavier elements, but, like the other giant planets in the Solar System, it lacks a well-defined solid surface. The outer atmosphere is divided into a series of latitudinal bands with turbulence and storms along their interacting boundaries. A prominent result of this is the Great Red Spot, a giant storm which has been observed since at least the 20th century.

Jupiter is surrounded by a faint planetary ring system and a powerful magnetosphere. Jupiter's magnetic tail is nearly 800 million km long, covering nearly the entire distance to Saturn's orbit. Jupiter has 82 known moons and likely many more, including the four large Galilean moons: Io, Europa, Ganymede, and Callisto. Io and Europa are about the size of Earth's Moon; Callisto is almost the size of the planet Mercury, and Ganymede is even larger.

Geography

Jupiter is a gas giant, being primarily composed of gas and liquid rather than solid matter. It is the largest planet in the Solar System, with a diameter of 142,984 km (88,846 mi) at its equator. The average density of Jupiter, 1.326 g/cm3, is about the same as maple syrup and is lower than those of the four terrestrial planets. Jupiter's mass is 2.5 times that of all the other planets in the Solar System combined—so massive that its barycentre with the Sun lies above the Sun's surface at 1.068 solar radii from the Sun's centre. Jupiter is much larger than Earth and considerably less dense: it has 1,321 times the volume of the Earth, but only 318 times the mass.  Jupiter's radius is about one tenth the radius of the Sun, and its mass is one thousandth the mass of the Sun, as the densities of the two bodies are similar. Theoretical models indicate that if Jupiter had over 40% more mass, the interior would be so compressed that its volume would decrease despite the increasing amount of matter. For smaller changes in its mass, the radius would not change appreciably. As a result, Jupiter is thought to have about as large a diameter as a planet of its composition and evolutionary history can achieve. The process of further shrinkage with increasing mass would continue until appreciable stellar ignition was achieved. Although Jupiter would need to be about 75 times more massive to fuse hydrogen and become a star, the smallest red dwarf may be only slightly larger in radius than Saturn.

Climate

Jupiter consists of a dense metallic core, a surrounding layer of liquid metallic hydrogen (with some helium) extending outward to about 80% of the radius of the planet, and an outer atmosphere consisting primarily of molecular hydrogen. Outside the layer of metallic hydrogen lies a transparent interior atmosphere of hydrogen. At this depth, the pressure and temperature are above molecular hydrogen's critical pressure of 1.3 MPa and critical temperature of 33 K (−240.2 °C; −400.3 °F). In this state, there are no distinct liquid and gas phases—hydrogen is said to be in a supercritical fluid state. The hydrogen and helium gas extending downward from the cloud layer gradually transitions to a liquid in deeper layers, possibly resembling something akin to an ocean of liquid hydrogen and other supercritical fluids. Physically, the gas gradually becomes hotter and denser as depth increases.
Rain-like droplets of helium and neon precipitate downward through the lower atmosphere, depleting the abundance of these elements in the upper atmosphere. Calculations suggest that helium drops separate from metallic hydrogen at a radius of 60,000 km (11,000 km below the cloudtops) and merge again at 50,000 km (22,000 km beneath the clouds). Pressure-cooked diamond "raindrops" precipitate throughout the cloud layer.
The temperature and pressure inside Jupiter increase steadily inward because the heat of planetary formation can only escape by convection. At a surface depth where the atmospheric pressure level is 1 bar (0.10 MPa), the temperature is around 165 K (−108 °C). The region of supercritical hydrogen changes gradually from a molecular fluid to a metallic fluid spans pressure ranges of 50–400 GPa with temperatures of 5,000–8,400 K (4,730–8,130 °C), respectively. The temperature of Jupiter's diluted core is estimated to be 20,000 K (19,700 °C) with a pressure of around 4,000 GPa.

Natural Resources

Jupiter's upper atmosphere is about 90% hydrogen and 10% helium by volume. Since helium atoms are more massive than hydrogen molecules, Jupiter's atmosphere is approximately 24% helium by mass. The atmosphere contains trace amounts of methane, water vapour, ammonia, and silicon-based compounds. There are also fractional amounts of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. The outermost layer of the atmosphere contains crystals of frozen ammonia. Through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found. The interior of Jupiter contains denser materials—by mass it is roughly 71% hydrogen, 24% helium, and 5% other elements.
The atmospheric proportions of hydrogen and helium are close to the theoretical composition of the primordial solar nebula. Neon in the upper atmosphere only consists of 20 parts per million by mass, which is about a tenth as abundant as in the Sun. Helium is also reduced to about 80% of the Sun's helium composition. This depletion is a result of precipitation of these elements as helium-rich droplets, a process that happens deep in the interior of the planet.
Based on spectroscopy, Saturn is thought to be similar in composition to Jupiter, but the other giant planets Uranus and Neptune have relatively less hydrogen and helium and relatively more of the next most common elements, including oxygen, carbon, nitrogen, and sulfur. These planets are known as ice giants, because the majority of their volatile compounds are in solid form.

History

Jupiter is believed to be the oldest planet in the Solar System. Current models of Solar System formation suggest that Jupiter formed at or beyond the snow line: a distance from the early Sun where the temperature is sufficiently cold for volatiles such as water to condense into solids. The planet began as a solid core, which then accumulated its gaseous atmosphere. As a consequence, the planet must have formed before the solar nebula was fully dispersed. During its formation, Jupiter's mass gradually increased until it had 20 times the mass of the Earth (about half of which was made up of silicates, ices and other heavy-element constituents). When the proto-Jupiter grew larger than 50 Earth masses it created a gap in the solar nebula. Thereafter, the growing planet reached its final masses in 3–4 million years.

Type

Planet

Included Locations

• Callisto
• Europa
• Ganymede
• Io