Jupiter

Jupiter is the largest planet in the Solar System, first gas planet and is also separated from the rock planets via the asteroid belt and is the fifth planet away from the Sun, with a considerable gap between it and Mars. This kind of space between planets also appears between Saturn, Uranus and Neptune, as well as other dwarf planets, like Pluto or Eris.

Pioneer 10 was the first spacecraft to visit Jupiter, making its closest approach to the planet in December 1973; Pioneer 10 identified plasma in Jupiter's magnetic field and also found that Jupiter's magnetic tail is nearly 800 million kilometers long, covering the entire distance to Saturn. Jupiter has been explored on a number of occasions by robotic spacecraft, beginning with the Pioneer and Voyager flyby missions from 1973 to 1979, and later by the Galileo orbiter, which arrived at Jupiter in 1995. In 2007, Jupiter was visited by the New Horizons probe, which used Jupiter's gravity to increase its speed and bend its trajectory en route to Pluto. The latest probe to visit the planet, Juno, entered orbit around Jupiter in July 2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of the moon Europa.

Jupiter is the third-brightest natural object in the Earth's night sky after the Moon and Venus. It has been observed since prehistoric times and is named after the Roman god Jupiter, the king of the gods, because of it's gigantic, enormous size. Jupiter's diameter is 11 times the diameter of Earth and this giant planet can fit 1.200 - 1.300 Earths inside it. With a mass 318 times that of Earth, Jupiter is (more than) 2,5 times more massive than all the planets of the Solar System combined in 1 gigantic mass. Yet, the mass of Jupiter is (just a little less than) 1% the mass of the Sun.

## Origins

Jupiter is most likely 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. It first assembled a large solid core before accumulating its gaseous atmosphere. As a consequence, the core must have formed before the solar nebula began to dissipate after 10 million years. Formation models suggest Jupiter grew to 20 times the mass of the Earth in under a million years. The orbiting mass created a gap in the disk, thereafter slowly increasing to 50 Earth masses in 3–4 million years.

As the young planet accreted mass, interaction with the gas disk orbiting the Sun, as well as orbital resonances with Saturn, caused it to migrate inward in what theorists call the grand tack hypothesis. This would have upset the orbits of what are believed to be super-Earths orbiting closer to the Sun, causing them to collide destructively. Jupiter's inward spiraling migration went on for around 700,000 years, during an epoch approximately 2–3 million years after the planet began to form. Once Jupiter and Saturn became locked in a 3:2 mean motion resonance, they migrated back out from the inner system to their current locations. This departure allowed the formation of the inner planets from the rubble, including Earth. However, the formation timescales of terrestrial planets resulting from the grand tack hypothesis appear inconsistent with the measured terrestrial composition. Moreover, the likelihood that the outward migration actually occurred in the solar nebula is very low. In fact, some models predict the formation of Jupiter's analogues whose properties are close to those of the planet at the current epoch.

## Composition

### Atmosphere

The **atmosphere of Jupiter** is the largest planetary atmosphere in the Solar System. Jupiter has the deepest planetary atmosphere in the Solar System, spanning over 5,000 km (3,000 mi) in altitude and this atmosphere is mostly made of molecular hydrogen and helium in roughly solar proportions; other chemical compounds are present only in small amounts and include methane, ammonia, hydrogen sulfide, and even water. Although water is thought to reside deep in the atmosphere, its directly measured concentration is very low and it is unknown whether water exists in the upper atmosphere of Jupiter. The nitrogen, sulfur, and noble gas abundances in Jupiter's atmosphere exceed solar values by a factor of about three.

The atmosphere of Jupiter lacks a clear lower boundary and gradually transitions into the liquid interior of the planet. From lowest to highest, the atmospheric layers are the troposphere, stratosphere, thermosphere and exosphere. Each layer has characteristic temperature gradients. The lowest layer, the troposphere, has a complicated system of clouds and hazes, comprising layers of ammonia, ammonium hydrosulfide and water. The upper ammonia clouds visible at Jupiter's surface are organized in a dozen zonal bands parallel to the equator and are bounded by powerful zonal atmospheric flows (winds) known as *jets*. The bands alternate in color: the dark bands are called *belts*, while light ones are called *zones*. Zones, which are colder than belts, correspond to upwellings, while belts mark descending gas. The zones' lighter color is believed to result from ammonia ice; what gives the belts their darker colors is uncertain. The origins of the banded structure and jets are not well understood, though a "shallow model" and a "deep model" exist.

The Jovian atmosphere shows a wide range of active phenomena, including band instabilities, vortices (cyclones and anticyclones), storms and lightning. The vortices reveal themselves as large red, white or brown spots (ovals). The largest two spots are the Great Red Spot (GRS) and Oval BA, which is also red. These two and most of the other large spots are anticyclonic. Smaller anticyclones tend to be white. Vortices are thought to be relatively shallow structures with depths not exceeding several hundred kilometers. Located in the southern hemisphere, the GRS is the largest known vortex in the Solar System. It could engulf two or three Earths and has existed for at least three hundred years. Oval BA, south of GRS, is a red spot a third the size of GRS that formed in 2000 from the merging of three white ovals.

Jupiter has powerful storms, often accompanied by lightning strikes. The storms are a result of moist convection in the atmosphere connected to the evaporation and condensation of water. They are sites of strong upward motion of the air, which leads to the formation of bright and dense clouds. The storms form mainly in belt regions. The lightning strikes on Jupiter are hundreds of times more powerful than those seen on Earth, and are assumed to be associated with the water clouds. Recent Juno observations suggest Jovian lightning strikes occur above the altitude of water clouds (3-7 bars). A charge separation between falling liquid ammonia-water droplets and water ice particles may generate the higher-altitude lightning. Upper-atmospheric lightning has also been observed 260 km above the 1 bar level. **Jupiter**'s upper atmosphere is composed of 3 layers that are 71 km high together, with the top having clouds of ammonia ice, middle having ammonium hydrosulfide and innermost layer having water, ice and water vapor. Rest is made out of primarily hydrogen and helium.**Jupiter**'s thick bands are comprised of gases that contain sulfur and phosphorus. This, and the *extremely fast rotation speeds separate these belts into darks and bright zones*. In the southern hemisphere, the big red spot can be located, which has been observed for over 300-400 years, *is around 2-3 times larger than Earth itself.*The composition of Jupiter's atmosphere is similar to that of the planet whole.

Jupiter's atmosphere is the most comprehensively understood of those of all the gas giants because it was observed directly by the *Galileo* atmospheric probe when it entered the Jovian atmosphere on December 7, 1995. Other sources of information about Jupiter's atmospheric composition include the Infrared Space Observatory (ISO), the *Galileo* and *Cassini* orbiters, and Earth-based observations. The two main constituents of the Jovian atmosphere are molecular hydrogen (H2) and helium. The helium abundance is 0.157 ± 0.004 relative to molecular hydrogen by number of molecules, and its mass fraction is 0.234 ± 0.005, which is slightly lower than the Solar System's primordial value. The reason for this low abundance is not entirely understood, but some of the helium may have condensed into the core of Jupiter. This condensation is likely to be in the form of helium rain: as hydrogen turns into the metallic state at depths of more than 10,000 km, helium separates from it forming droplets which, being denser than the metallic hydrogen, descend towards the core. This can also explain the severe depletion of neon (see Table), an element that easily dissolves in helium droplets and would be transported in them towards the core as well.

Coherently related *S* (2.3 GHz) and *X* band (8.4 GHz) signals transmitted from Voyager 1 and 2 have been used to probe the Jovian atmosphere during occultations of the spacecraft by Jupiter. The observations have yielded profiles in height of the gas refractivity, molecular number density, pressure, temperature, and microwave absorption in the troposphere and stratosphere of Jupiter at latitudes ranging from 0° to about 70°S. The data cover a pressure range from 1000 to 1 mbar over a height interval of 160 km. At the 1000-mbar level, the temperature was 165±5 K, and the lapse rate was equal to the adiabatic value of 2.1 K/km, within the resolution of the measurements. The ammonia abundance in this region of the atmosphere was about 0.022±0.008%, in approximate agreement with the value derived from cosmic abundance considerations. The tropopause, which was detected near the 140-mbar level, had a temperature of 110 K. Above the tropopause, the temperature increased with increasing altitude, reaching 160±20 K in the 10- to 1-mbar region of the stratosphere. Significant horizontal density variations were detected in the stratosphere. This may imply a nonuniform temperature and aerosol distribution across the Jovian disk or high- and low-pressure regions due to local atmospheric dynamics. The zenoid or gravity equipotential surface which best fits the 100-mbar isobaric surface has an equatorial radius of 71,541±4 km and a polar radius of 66,896±4 km.

The atmosphere contains various simple compounds such as water, methane (CH4), hydrogen sulfide (H2S), ammonia (NH3) and phosphine (PH3). Their abundances in the deep (below 10 bar) troposphere imply that the atmosphere of Jupiter is enriched in the elements carbon, nitrogen, sulfur and possibly oxygen by factor of 2–4 relative to the Sun. The noble gases argon, krypton and xenon also appear in abundance relative to solar levels (see table), while neon is scarcer. Other chemical compounds such as arsine (AsH3) and germane (GeH4) are present only in trace amounts. The upper atmosphere of Jupiter contains small amounts of simple hydrocarbons such as ethane, acetylene, and diacetylene, which form from methane under the influence of the solar ultraviolet radiation and charged particles coming from Jupiter's magnetosphere. The carbon dioxide, carbon monoxide and water present in the upper atmosphere are thought to originate from impacting comets, such as Shoemaker-Levy 9. The water cannot come from the troposphere because the cold tropopause acts like a cold trap, effectively preventing water from rising to the stratosphere (see Vertical structure above). Earth- and spacecraft-based measurements have led to improved knowledge of the isotopic ratios in Jupiter's atmosphere. As of July 2003, the accepted value for the deuterium abundance is (2.25 ± 0.35) × 10−5, which probably represents the primordial value in the protosolar nebula that gave birth to the Solar System. The ratio of nitrogen isotopes in the Jovian atmosphere, 15N to 14N, is 2.3 × 10−3, a third lower than that in the Earth's atmosphere (3.5 × 10−3). The latter discovery is especially significant since the previous theories of Solar System formation considered the terrestrial value for the ratio of nitrogen isotopes to be primordial.

Every 15–17 years Jupiter is marked by especially powerful storms. They appear at 23°N latitude, where the strongest eastward jet, that can reach 150 m/s, is located. The last time such an event was observed was in March–June 2007. Two storms appeared in the northern temperate belt 55° apart in longitude. They significantly disturbed the belt. The dark material that was shed by the storms mixed with clouds and changed the belt's color. The storms moved with a speed as high as 170 m/s, slightly faster than the jet itself, hinting at the existence of strong winds deep in the atmosphere.

### Internal structure

Before the early 21st century, most scientists expected Jupiter to either consist of a dense 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 predominantly of molecular hydrogen, or perhaps to have no core at all, consisting instead of denser and denser fluid (predominantly molecular and metallic hydrogen) all the way to the center, depending on whether the planet accreted first as a solid body or collapsed directly from the gaseous protoplanetary disk. When the *Juno* mission arrived in July 2016, it found that Jupiter has a very diffuse core that mixes into its mantle. A possible cause is an impact from a planet of about ten Earth masses a few million years after Jupiter's formation, which would have disrupted an originally solid Jovian core. It is estimated that the core is 30–50% of the planet's radius, and contains heavy elements 7–25 times the mass of Earth.

Above the layer of metallic hydrogen lies a transparent interior atmosphere of hydrogen. At this depth, the pressure and temperature are above hydrogen's critical pressure of 1.2858 MPa and critical temperature of only 32.938 K. In this state, there are no distinct liquid and gas phases—hydrogen is said to be in a supercritical fluid state. It is convenient to treat hydrogen as gas extending downward from the cloud layer to a depth of about 1,000 km, and as liquid in deeper layers. Physically, there is no clear boundary—the gas smoothly 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. Rainfalls of diamonds have been suggested to occur, as well as on Saturn and the ice giants Uranus and Neptune.

The temperature and pressure inside Jupiter increase steadily inward, this is observed in microwave emission and required because the heat of formation can only escape by convection. At the pressure level of 10 bars (1 MPa), the temperature is around 340 K (67 °C; 152 °F). The hydrogen is always supercritical (that is, it never encounters a first-order phase transition) even as it changes gradually from a molecular fluid to a metallic fluid at around 100–200 GPa, where the temperature is perhaps 5,000 K (4,730 °C; 8,540 °F). The temperature of Jupiter's diluted core is estimated at around 20,000 K (19,700 °C; 35,500 °F) or more with an estimated pressure of around 4,500 GPa.

The problem with finding an adequate model of Jupiter's internal structure is due to the extreme condition that are exerted upon hydrogen and helium inside of Jupiter. Scientists haven't done extensive research on what happens when temperatures of 24,700 °C and pressures of up to 100 million atmospheres are acted upon hydrogen and helium. Despite this, we know that hydrogen is expected to be metallic and conductive at depths of a quarter of Jupiter, however, the core itself is around a third the size of Earth, its composition is thought to be rocky and icy, but unknown.

Jupiter has the largest ocean of any planet and celestial body in the entire Solar System, as between the gaseous surface of the gigantic planet and the core, there is an enormous ocean of metallic hydrogen. There are very high temperatures down there, and lightning, creating plasma. This metallic is liquid or semi-liquid, but very hot and plasma. Scientists do believe that Jupiter *kinda has evidence of nuclear fusion like stars ans the Sun,* and they also say that similar conditions occur in the interior of Neptune as well. They do not have different opinions about the interiors of Uranus and Saturn, as again, scientists who studied all the the four gas giant planets, know that there is metallic hydrogen in the interiors of all the four giants, above their cores, bellow their gaseous surfaces, with Jupiter having the largest ocean of all.

## Great Red Spot

The **Great Red Spot** is a persistent high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm that is the largest in the Solar System. Located 22 degrees south of Jupiter's equator, it produces wind-speeds up to 432 km/h (268 mph). Observations from 1665 to 1713 are believed to be of the same storm; if this is correct, it has existed for at least 356 years. It was next observed in September 1831, with 60 recorded observations between then and 1878 when continuous observations began. The Great Red Spot may have existed since before 1665, but the present spot was first seen only after 1830, and well-studied only after a prominent apparition in 1879. The storm that was seen in the 17th century may have been different than the storm that exists today. A long gap separates its period of current study after 1830 from its 17th century discovery. Whether the original spot dissipated and reformed, whether it faded, or if the observational record was simply poor is unknown. For example, the first sighting of the Great Red Spot is often credited to Robert Hooke, who described a spot on the planet in May 1664. However, it is likely that Hooke's spot was in another belt altogether (the North Equatorial Belt, as opposed to the current Great Red Spot's location in the South Equatorial Belt). Much more convincing is Giovanni Cassini's description of a "permanent spot" the following year. With fluctuations in visibility, Cassini's spot was observed from 1665 to 1713, but the 118-year observational gap makes the identity of the two spots inconclusive. The older spot's shorter observational history and slower motion than the modern spot makes it difficult to conclude that they are the same. In the 21st century, the Great Red Spot was seen to be shrinking in size. At the start of 2004, it had approximately half the longitudinal extent it had a century ago, when it reached a size of 40,000 km (25,000 mi), about three times the diameter of Earth. At the present rate of reduction, it would become circular by 2040. It is not known how long the spot will last, or whether the change is a result of normal fluctuations. In 2019, the Great Red Spot began "flaking" at its edge, with fragments of the storm breaking off and dissipating. The shrinking and "flaking" fueled concern from some astronomers that the Great Red Spot could dissipate within 20 years. However, other astronomers believe that the apparent size of the Great Red Spot reflects its cloud coverage and not the size of the actual, underlying vortex, and they also believe that the flaking events can be explained by interactions with other cyclones or anticyclones, including incomplete absorptions of smaller systems; if this is the case, this would mean that the Great Red Spot is not in danger of dissipating. Jupiter's Great Red Spot rotates counterclockwise, with a period of about six Earth days or fourteen Jovian days. Measuring 16,350 km (10,160 mi) in width as of 3 April 2017, Jupiter's Great Red Spot is 1.3 times the diameter of Earth. The cloud-tops of this storm are about 8 km (5.0 mi) above the surrounding cloud-tops. Infrared data have long indicated that the Great Red Spot is colder (and thus higher in altitude) than most of the other clouds on the planet. The upper atmosphere above the storm, however, has substantially higher temperatures than the rest of the planet. Acoustic (sound) waves rising from the turbulence of the storm below have been proposed as an explanation for the heating of this region. Careful tracking of atmospheric features revealed the Great Red Spot's counter-clockwise circulation as far back as 1966, observations dramatically confirmed by the first time-lapse movies from the *Voyager* fly-bys. The spot is confined by a modest eastward jet stream to its south and a very strong westward one to its north. Though winds around the edge of the spot peak at about 432 km/h (268 mph), currents inside it seem stagnant, with little inflow or outflow. The rotation period of the spot has decreased with time, perhaps as a direct result of its steady reduction in size. The Great Red Spot's latitude has been stable for the duration of good observational records, typically varying by about a degree. Its longitude, however, is subject to constant variation. Because Jupiter does not rotate uniformly at all latitudes, astronomers have defined three different systems for defining the longitude. System II is used for latitudes of more than 10 degrees and was originally based on the average rotational period of the Great Red Spot of 9h 55m 42s. Despite this, however, the spot has "lapped" the planet in System II at least 10 times since the early nineteenth century. Its drift rate has changed dramatically over the years and has been linked to the brightness of the South Equatorial Belt and the presence or absence of a South Tropical Disturbance. Jupiter is known and famous for it's Giant Red Spot..Scientists think that it formed about 300 - 400 years ago.

## Moons

**Jupiter** used to have the most moons, until relatively recently, *20 new moons were discovered orbiting Saturn*, which makes it have **82**, 3 higher than **Jupiter's** **79**.**Jupiter**'s moons are some of the largest, having the largest: Ganymede, which is larger than Pluto, our Moon and even Mercury. With Jupiter having so many moons, understandably, many of them will be insignificant and barely visible. 26 moons are currently awaiting their official names. In 1610, Galileo Galilei discovered the 4 Galilean moons, Ganymede, Io, Callisto and Europa which, along with our moon, and Saturn's moon Titan are the largest and most massive moons in the entire solar system. Europa is the only moon smaller than our Moon, 3100 vs 3474 km in diameter. Ganymede, Europa and Callisto have icy surfaces with liquid oceans underneath, and Io has volcanoes on it's surface that spit sulfuric acid. Of Jupiter's moons, eight are regular satellites with prograde and nearly circular orbits that are not greatly inclined with respect to Jupiter's equatorial plane. The Galilean satellites are nearly spherical in shape due to their planetary mass, and so would be considered at least dwarf planets if they were in direct orbit around the Sun. The other four regular satellites are much smaller and closer to Jupiter; these serve as sources of the dust that makes up Jupiter's rings. The remainder of Jupiter's moons are irregular satellites whose prograde and retrograde orbits are much farther from Jupiter and have high inclinations and eccentricities. These moons were probably captured by Jupiter from solar orbits. 22 of the irregular satellites have not yet been officially named.

## Rings

The planet Jupiter has a system of rings known as the **rings of Jupiter** or the **Jovian ring system**. It was the third ring system to be discovered in the Solar System, after those of Saturn and Uranus. It was first observed in 1979 by the *Voyager 1* space probe and more thoroughly investigated in the 1990s by the *Galileo* orbiter. It has also been observed by the Hubble Space Telescope and from Earth for several years. Ground-based observation of the rings requires the largest available telescopes. The Jovian ring system is faint and consists mainly of dust. It has four main components: a thick inner torus of particles known as the "halo ring"; a relatively bright, exceptionally thin "main ring"; and two wide, thick and faint outer "gossamer rings", named for the moons of whose material they are composed: Amalthea and Thebe. The main and halo rings consist of dust ejected from the moons Metis, Adrastea, and other unobserved parent bodies as the result of high-velocity impacts. High-resolution images obtained in February and March 2007 by the *New Horizons* spacecraft revealed a rich fine structure in the main ring.

In visible and near-infrared light, the rings have a reddish color, except the halo ring, which is neutral or blue in color. The size of the dust in the rings varies, but the cross-sectional area is greatest for nonspherical particles of radius about 15 μm in all rings except the halo. The halo ring is probably dominated by submicrometre dust. The total mass of the ring system (including unresolved parent bodies) is poorly known, but is probably in the range of 1011 to 1016 kg. The age of the ring system is not known, but it may have existed since the formation of Jupiter. A ring could possibly exist in Himalia's orbit. One possible explanation is that a small moon had crashed into Himalia and the force of the impact caused material to blast off Himalia.