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4 juillet 2011 1 04 /07 /juillet /2011 05:28

Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with a mass slightly less than one-thousandth of the Sun but is two and a half times the mass of all the other planets in our Solar System combined.HP 586006-321 Battery

Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian or outer planets.

The planet was known by astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures.HP 586006-361 Battery

The Romansnamed the planet after the Roman god Jupiter.[14] When viewed from Earth, Jupiter can reach an apparent magnitude of ?2.94, making it on average the third-brightest object in the night sky after the Moon and Venus. (Mars can briefly match Jupiter's brightness at certain points in its orbit.)HP 586028-341 Battery

Jupiter is primarily composed of hydrogen with a quarter of its mass being helium; it may also have a rocky core of heavier elements. Because of its rapid rotation, Jupiter's shape is that of an oblate spheroid (it possesses a slight but noticeable bulge around the equator). HP h588178-141 Battery

The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope.HP 593553-001 Battery

Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 64 moons, including the four large moons called theGalilean moons that were first discovered by Galileo Galilei in 1610. Ganymede, the largest of these moons, has a diameter greater than that of the planet Mercury.HP 593554-001 Battery

Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. The most recent probe to visit Jupiter was the Pluto-bound New Horizons spacecraft in late February 2007. HP HSTNN-CB0W Battery

The probe used the gravity from Jupiter to increase its speed. Future targets for exploration in the Jovian system include the possible ice-covered liquid ocean on the moon Europa.HP HSTNN-CB0X Battery


Jupiter is composed primarily of gaseous and liquid matter. It is the largest of four gas giants as well as the largest planet in the solar system with a diameter of 142,984 km at its equator. The density of Jupiter, 1.326 g/cm3, is the second highest of the gas giant planets. However, the density is lower than any of the four terrestrial planets.HP HSTNN-I79C Battery


Jupiter's upper atmosphere is composed of about 88–92% hydrogen and 8–12% helium by percent volume or fraction of gas molecules (see table to the right). Since a helium atom has about four times as much mass as a hydrogen atom, the composition changes when described as the proportion of mass contributed by different atoms. HP HSTNN-I81C Battery

Thus the atmosphere is approximately 75% hydrogen and 24% helium by mass, with the remaining one percent of the mass consisting of other elements. The interior contains denser materials such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass. HP HSTNN-IB0N Battery

The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. The outermost layer of the atmosphere contains crystals of frozen ammonia.HP HSTNN-IB0X Battery

Through infrared and ultraviolet measurements, trace amounts of benzene and otherhydrocarbons have also been found.

The atmospheric proportions of hydrogen and helium are very close to the theoretical composition of the primordial solar nebula.HP HSTNN-LB0W Battery

However, 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.[18] Helium is also depleted, although only to about 80% of the Sun's helium composition. This depletion may be a result of precipitation of these elements into the interior of the planet.HP HSTNN-OB0X Battery

Abundances of heavier inert gases in Jupiter's atmosphere are about two to three times that of the Sun.

Based on spectroscopy, Saturn is thought to be similar in composition to Jupiter, but the other gas giants Uranus and Neptune have relatively much less hydrogen and helium.HP HSTNN-OB0Y Battery

However, because of the lack of atmospheric entry probes, high quality abundance numbers of the heavier elements are lacking for the outer planets beyond Jupiter.


Jupiter's mass is 2.5 times that of all the other planets in our Solar System combined—this is so massive that its barycenter with the Sun lies above the Sun's surface at 1.068 solar radii from the Sun's center.HP HSTNN-Q61C Battery

Although this planet dwarfs the Earth with a diameter 11 times as great, it is considerably less dense. Jupiter's volume is that of about 1,321 Earths, yet the planet is only 318 times as massive. Jupiter's radius is about 1/10 the radius of the Sun,[22] and its mass is 0.001 times the mass of the Sun, so the density of the two bodies is similar.HP HSTNN-Q62C Battery

A "Jupiter mass" (MJ or MJup) is often used as a unit to describe masses of other objects, particularly extrasolar planets and brown dwarfs. So, for example, the extrasolar planet HD 209458 b has a mass of 0.69 MJ, while COROT-7b has a mass of 0.015 MJ.HP HSTNN-YB0X Battery

Theoretical models indicate that if Jupiter had much more mass than it does at present, the planet would shrink. For small changes in mass, the radiuswould not change appreciably, and above about 500 M? (1.6 Jupiter masses)  the interior would become so much more compressed under the increased gravitation force that the planet's volume would decrease despite the increasing amount of matter.HP NBP6A174B1 Battery

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 is achieved as in high-mass brown dwarfs around 50 Jupiter masses.HP HSTNN-YB0X Battery

This has led some astronomers to term it a "failed star" , although it is unclear whether the processes involved in the formation of planets like Jupiter are similar to the processes involved in the formation of multiple star systems.

Although Jupiter would need to be about 75 times as massive to fuse hydrogen and become a star, the smallest red dwarf is only about 30 percent larger in radius than Jupiter.HP NBP6A174 Battery

Despite this, Jupiter still radiates more heat than it receives from the Sun; the amount of heat produced inside the planet is similar to the total solar radiation it receives. This additional heat radiation is generated by the Kelvin–Helmholtz mechanism through adiabatic contraction. HP NBP6A174B1 Battery

This process results in the planet shrinking by about 2 cm each year. When it was first formed, Jupiter was much hotter and was about twice its current diameter.

Internal structure

Jupiter is thought to consist of a dense core with a mixture of elements, a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly of molecular hydrogen.HP NBP6A175 Battery

Beyond this basic outline, there is still considerable uncertainty. The core is often described as rocky, but its detailed composition is unknown, as are the properties of materials at the temperatures and pressures of those depths (see below). HP NBP6A175B1 Battery

In 1997, the existence of the core was suggested by gravitational measurements, indicating a mass of from 12 to 45 times the Earth's mass or roughly 3%–15% of the total mass of Jupiter.  The presence of a core during at least part of Jupiter's history is suggested by models of planetary formation involving initial formation of a rocky or icy core that is massive enough to collect its bulk of hydrogen and helium from the protosolar nebula.HP WD548AA Battery

Assuming it did exist, it may have shrunk as convection currents of hot liquid metallic hydrogen mixed with the molten core and carried its contents to higher levels in the planetary interior. A core may now be entirely absent, as gravitational measurements are not yet precise enough to rule that possibility out entirely.HP WD549AA Battery

The uncertainty of the models is tied to the error margin in hitherto measured parameters: one of the rotational coefficients (J6) used to describe the planet's gravitational moment, Jupiter's equatorial radius, and its temperature at 1 bar pressure. The JUNO mission, scheduled for launch in 2011, is expected to narrow down the value of these parameters, and thereby make progress on the problem of the core.HP Envy 17 Notebook PC Battery

The core region is surrounded by dense metallic hydrogen, which extends outward to about 78 percent of the radius of the planet.[29] Rain-like droplets of helium and neon precipitate downward through this layer, depleting the abundance of these elements in the upper atmosphere.HP Envy 17T Battery

Above the layer of metallic hydrogen lies a transparent interior atmosphere of hydrogen. At this depth, the temperature is above the critical temperature, which for hydrogen is only 33 K (see hydrogen). In this state, there are no distinct liquid and gas phases - hydrogen is said to be in a supercritical fluid state. HP HSTNN-Q61C Battery

However, it is convenient to treat hydrogen as gas in the upper layer extending downward from the cloud layer to a depth of about 1,000 km,[29] and as liquid in deeper layers. Physically, there is no clear boundary—gas smoothly becomes hotter and denser as one descends.HP GSTNN-Q62C Battery

The temperature and pressure inside Jupiter increase steadily toward the core. At the phase transition region where hydrogen—heated beyond its critical point—becomes metallic, it is believed the temperature is 10,000 K and the pressure is 200 GPa. HP HSTNN-IB1E Battery

The temperature at the core boundary is estimated to be 36,000 K and the interior pressure is roughly 3,000–4,500 GPa.


Jupiter has the largest planetary atmosphere in the Solar System, spanning over 5000 km in altitude.HP HSTNN-IB0X Battery

As Jupiter has no surface, the base of its atmosphere is usually considered to be the point at which atmospheric pressure is equal to 10 bars, or ten times surface pressure on Earth.

Cloud layers

Jupiter is perpetually covered with clouds composed of ammonia crystals and possibly ammonium hydrosulfide. HP HSTNN-OB0X Battery

The clouds are located in thetropopause and are arranged into bands of different latitudes, known as tropical regions. These are sub-divided into lighter-hued zones and darker belts. The interactions of these conflicting circulation patterns cause storms and turbulence. Wind speeds of 100 m/s (360 km/h) are common in zonal jets.HP HSTNN-YB0X Battery

The zones have been observed to vary in width, color and intensity from year to year, but they have remained sufficiently stable for astronomers to give them identifying designations.

The cloud layer is only about 50 km deep, and consists of at least two decks of clouds: a thick lower deck and a thin clearer region.HP 586006-361 Battery

There may also be a thin layer of water clouds underlying the ammonia layer, as evidenced by flashes of lightning detected in the atmosphere of Jupiter. This is caused by water's polarity, which makes it capable of creating the charge separation needed to produce lightning.HP NBP6A174 Battery

These electrical discharges can be up to a thousand times as powerful as lightning on the Earth.The water clouds can form thunderstorms driven by the heat rising from the interior.

The orange and brown coloration in the clouds of Jupiter are caused by upwelling compounds that change color when they are exposed to ultraviolet light from the Sun.HP NBP6A174B1 Battery

The exact makeup remains uncertain, but the substances are believed to be phosphorus, sulfur or possibly hydrocarbons.[29][44]These colorful compounds, known as chromophores, mix with the warmer, lower deck of clouds. The zones are formed when rising convection cells form crystallizing ammonia that masks out these lower clouds from view.HP 588178-141 Battery

Jupiter's low axial tilt means that the poles constantly receive less solar radiation than at the planet's equatorial region. Convection within the interior of the planet transports more energy to the poles, however, balancing out the temperatures at the cloud layer.[HP Pavilion dv5 Adapter

Great Red Spot and other vortices

The best known feature of Jupiter is the Great Red Spot, a persistent anticyclonic storm located 22° south of the equator that is larger than Earth. It is known to have been in existence since at least 1831,  and possibly since 1665.Sony NP-F330 Battery

Mathematical models suggest that the storm is stable and may be a permanent feature of the planet.[49] The storm is large enough to be visible through Earth-based telescopes with an aperture of 12 cm or larger.[50]

The oval object rotates counterclockwise, with a period of about six days.Asus Eee PC 904HA Adapter

The Great Red Spot's dimensions are 24–40,000 km × 12–14,000 km. It is large enough to contain two or three planets of Earth's diameter.[52] The maximum altitude of this storm is about 8 km above the surrounding cloudtops.[Nikon D80  Battery

Storms such as this are common within the turbulent atmospheres of gas giants. Jupiter also has white ovals and brown ovals, which are lesser unnamed storms. White ovals tend to consist of relatively cool clouds within the upper atmosphere. Brown ovals are warmer and located within the "normal cloud layer". Such storms can last as little as a few hours or stretch on for centuries.Sony PCGA-AC19V9 Adapter

Even before Voyager proved that the feature was a storm, there was strong evidence that the spot could not be associated with any deeper feature on the planet's surface, as the Spot rotates differentially with respect to the rest of the atmosphere, sometimes faster and sometimes more slowly. Dell T555C Battery

During its recorded history it has traveled several times around the planet relative to any possible fixed rotational marker below it.

In 2000, an atmospheric feature formed in the southern hemisphere that is similar in appearance to the Great Red Spot, but smaller.HP Pavilion DV6-3013SL Battery

This was created when several smaller, white oval-shaped storms merged to form a single feature—these three smaller white ovals were first observed in 1938. The merged feature was namedOval BA, and has been nicknamed Red Spot Junior. It has since increased in intensity and changed color from white to red. HP Pavilion DV7-2085EL Battery

Planetary rings

Jupiter has a faint planetary ring system composed of three main segments: an inner torus of particles known as the halo, a relatively bright main ring, and an outer gossamer ring. These rings appear to be made of dust, rather than ice as with Saturn's rings.HP Pavilion DV9700 Battery

The main ring is probably made of material ejected from the satellites Adrasteaand Metis. Material that would normally fall back to the moon is pulled into Jupiter because of its strong gravitational influence. The orbit of the material veers towards Jupiter and new material is added by additional impacts.HP Mini 702EA Battery

In a similar way, the moons Thebe and Amalthea probably produce the two distinct components of the dusty gossamer ring.[58]There is also evidence of a rocky ring strung along Amalthea's orbit which may consist of collisional debris from that moon.[HP Pavilion DV7-1120EO Battery


Jupiter's broad magnetic field is 14 times as strong as the Earth's, ranging from 4.2 gauss (0.42 mT) at the equator to 10–14 gauss (1.0–1.4 mT) at the poles, making it the strongest in the Solar System (except for sunspots). This field is believed to be generated by eddy currents—swirling movements of conducting materials—within the metallic hydrogen core. HP Compaq 491278-001 Battery

The volcanoes on the moon Io emit large amounts of sulfur dioxide forming a gas torus along the moon's orbit. The gas is ionized in the magnetosphere producing sulfur and oxygen ions. They, together with hydrogen ions originating from the atmosphere of Jupiter, form a plasma sheet in Jupiter's equatorial plane. HP Pavilion DV6-1030US Battery

The plasma in the sheet co-rotates with the planet causing deformation of the dipole magnetic field into that of magnetodisk. Electrons within the plasma sheet generate a strong radio signature that produces bursts in the range of 0.6–30 MHz.HP Compaq 490306-001 Battery

At about 75 Jupiter radii from the planet, the interaction of the magnetosphere with the solar wind generates a bow shock. Surrounding Jupiter's magnetosphere is a magnetopause, located at the inner edge of a magnetosheath—a region between it and the bow shock. HP Pavilion DV5-1211EM Battery

The solar wind interacts with these regions, elongating the magnetosphere on Jupiter's lee side and extending it outward until it nearly reaches the orbit of Saturn. The four largest moons of Jupiter all orbit within the magnetosphere, which protects them from the solar wind.HP EliteBook 2530P Battery

The magnetosphere of Jupiter is responsible for intense episodes of radio emission from the planet's polar regions. Volcanic activity on the Jovian moon Io (see below) injects gas into Jupiter's magnetosphere, producing a torus of particles about the planet. HP Pavilion DV4385EA Battery

As Io moves through this torus, the interaction generates Alfvén waves that carry ionized matter into the polar regions of Jupiter. As a result, radio waves are generated through a cyclotron maser mechanism, and the energy is transmitted out along a cone-shaped surface.Compaq PP2100 Battery

When the Earth intersects this cone, the radio emissions from Jupiter can exceed the solar radio output.

Orbit and rotation

Jupiter is the only planet that has a center of mass with the Sun that lies outside the volume of the Sun, though by only 7% of the Sun's radius.HP Compaq KU532AA Battery

The average distance between Jupiter and the Sun is 778 million km (about 5.2 times the average distance from the Earth to the Sun, or 5.2 AU) and it completes an orbit every 11.86 years. This is two-fifths the orbital period of Saturn, forming a 5:2 orbital resonance between the two largest planets in the Solar System.HP Pavilion DV6-1270EQ Battery

The elliptical orbit of Jupiter is inclined 1.31° compared to the Earth. Because of an eccentricity of 0.048, the distance from Jupiter and the Sun varies by 75 million km between perihelion and aphelion, or the nearest and most distant points of the planet along the orbital path respectively.HP Pavilion DV4385EA Battery

The axial tilt of Jupiter is relatively small: only 3.13°. As a result this planet does not experience significant seasonal changes, in contrast to Earth and Mars for example.

Jupiter's rotation is the fastest of all the Solar System's planets, completing a rotation on its axis in slightly less than ten hours; HP Compaq Business  NC4400 Battery

this creates an equatorial bulge easily seen through an Earth-based amateur telescope. This rotation requires a centripetal acceleration at the equator of about 1.67 m/s2, compared to the equatorial surface gravity of 24.79 m/s2; thus the net acceleration felt at the equatorial surface is only about 23.12 m/s2. HP Pavilion ZD8227 Battery

The planet is shaped as anoblate spheroid, meaning that the diameter across its equator is longer than the diameter measured between its poles. On Jupiter, the equatorial diameter is 9275 km longer than the diameter measured through the poles.[38]

Because Jupiter is not a solid body, its upper atmosphere undergoes differential rotation. Nikon D200 Battery

The rotation of Jupiter's polar atmosphere is about 5 minutes longer than that of the equatorial atmosphere; three systems are used as frames of reference, particularly when graphing the motion of atmospheric features. System I applies from the latitudes 10° N to 10° S; its period is the planet's shortest, at 9h 50m 30.0s. Acer PA-1650-02 Adapter

System II applies at all latitudes north and south of these; its period is 9h 55m 40.6s. System III was first defined by radio astronomers, and corresponds to the rotation of the planet's magnetosphere; its period is Jupiter's official rotation.Sony CYBER-SHOT DSC-T10  Battery


Jupiter is usually the fourth brightest object in the sky (after the Sun, the Moon and Venus);[45] however at times Mars appears brighter than Jupiter. Depending on Jupiter's position with respect to the Earth, it can vary in visual magnitude from as bright as ?2.9 at opposition down to ?1.6 during conjunctionwith the Sun. HP Compaq Business 6715b Battery

The angular diameter of Jupiter likewise varies from 50.1 to 29.8 arc seconds.[5] Favorable oppositions occur when Jupiter is passing through perihelion, an event that occurs once per orbit. As Jupiter approaches perihelion in March 2011, there was a favorable opposition in September 2010.Kodak KLIC-7004 Battery

Earth overtakes Jupiter every 398.9 days as it orbits the Sun, a duration called the synodic period. As it does so, Jupiter appears to undergo retrograde motion with respect to the background stars. That is, for a period Jupiter seems to move backward in the night sky, performing a looping motion.Acer Aspire 5920G Adapter

Jupiter's 12-year orbital period corresponds to the dozen astrological signs of the zodiac, and may have been the historical origin of the signs.[21] That is, each time Jupiter reaches opposition it has advanced eastward by about 30°, the width of a zodiac sign.Canon Digital IXUS 90 IS Battery

Because the orbit of Jupiter is outside the Earth's, the phase angle of Jupiter as viewed from the Earth never exceeds 11.5°. That is, the planet always appears nearly fully illuminated when viewed through Earth-based telescopes. It was only during spacecraft missions to Jupiter that crescent views of the planet were obtained.HP 2133 Mini-Note PC Adapter

Pre-telescopic research

The observation of Jupiter dates back to the Babylonian astronomers of the 7th or 8th century BCE.[68] The Chinese historian of astronomy, Xi Zezong, has claimed that Gan De, a Chinese astronomer, made the discovery of one of Jupiter's moons in 362 BCE with the unaided eye. If accurate, this would predate Galileo's discovery by nearly two millennia.Toshiba PA3536U-1BRS Battery

In his second century work the Almagest, the Hellenistic astronomer Claudius Ptolemaeus constructed ageocentric planetary model based on deferents and epicycles to explain Jupiter's motion relative to the Earth, giving its orbital period around the Earth as 4332.38 days, or 11.86 years.HP Compaq Business NX6110 Battery

In 499, Aryabhata, a mathematician-astronomer from the classical age of Indian mathematics and astronomy, also used a geocentric model to estimate Jupiter's period as 4332.2722 days, or 11.86 years.

Ground-based telescope research

In 1610, Galileo Galilei discovered the four largest moons of Jupiter - Io, Europa, Ganymede and Callisto (now known as the Galilean moons) - using a telescope;HP Pavilion DV9000 Adapter

thought to be the first telescopic observation of moons other than Earth's. Galileo's was also the first discovery of a celestial motion not apparently centered on the Earth. It was a major point in favor of Copernicus' heliocentric theory of the motions of the planets; Galileo's outspoken support of the Copernican theory placed him under the threat of the Inquisition.Dell Studio 1537 Battery

During the 1660s, Cassini used a new telescope to discover spots and colorful bands on Jupiter and observed that the planet appeared oblate; that is, flattened at the poles. He was also able to estimate the rotation period of the planet.[16] In 1690 Cassini noticed that the atmosphere undergoes differential rotation.HP PPP009H Adapter

The Great Red Spot, a prominent oval-shaped feature in the southern hemisphere of Jupiter, may have been observed as early as 1664 by Robert Hooke and in 1665 by Giovanni Cassini, although this is disputed. The pharmacist Heinrich Schwabe produced the earliest known drawing to show details of the Great Red Spot in 1831.Sony VGP-BPS8 Battery

The Red Spot was reportedly lost from sight on several occasions between 1665 and 1708 before becoming quite conspicuous in 1878. It was recorded as fading again in 1883 and at the start of the twentieth century.

Both Giovanni Borelli and Cassini made careful tables of the motions of the Jovian moons, allowing predictions of the times when the moons would pass before or behind the planet.Dell PA-12 Adapter

By the 1670s, however, it was observed that when Jupiter was on the opposite side of the Sun from the Earth, these events would occur about 17 minutes later than expected. Ole Rømer deduced that sight is not instantaneous (a conclusion that Cassini had earlier rejected[16]), and this timing discrepancy was used to estimate the speed of light.Sony Cyber-shot DSC-T7/B  Battery

In 1892, E. E. Barnard observed a fifth satellite of Jupiter with the 36-inch (910 mm) refractor at Lick Observatory in California. The discovery of this relatively small object, a testament to his keen eyesight, quickly made him famous. The moon was later named Amalthea.Dell LATITUDE M65 Battery

It was the last planetary moon to be discovered directly by visual observation.[78] An additional eight satellites were subsequently discovered before the flyby of the Voyager 1 probe in 1979.

In 1932, Rupert Wildt identified absorption bands of ammonia and methane in the spectra of Jupiter. HP Compaq 6720s Adapter

Three long-lived anticyclonic features termed white ovals were observed in 1938. For several decades they remained as separate features in the atmosphere, sometimes approaching each other but never merging. Finally, two of the ovals merged in 1998, then absorbed the third in 2000, becoming Oval BA.Acer AS07B41 Battery

Radiotelescope research

In 1955, Bernard Burke and Kenneth Franklin detected bursts of radio signals coming from Jupiter at 22.2 MHz.  The period of these bursts matched the rotation of the planet, and they were also able to use this information to refine the rotation rate. Sony VGP-BPL13 Battery

Radio bursts from Jupiter were found to come in two forms: long bursts (or L-bursts) lasting up to several seconds, and short bursts (or S-bursts) that had a duration of less than a hundredth of a second.[81]

Scientists discovered that there were three forms of radio signals transmitted from Jupiter.Sony VGP-BPS13 Battery

  • Decametric radio bursts (with a wavelength of tens of meters) vary with the rotation of Jupiter, and are influenced by interaction of Io with Jupiter's magnetic field.[82]
  • Decimetric radio emission (with wavelengths measured in centimeters) was first observed by Frank Drake and Hein Hvatum in 1959.Sony VGP-BPS13/B Battery
  • The origin of this signal was from a torus-shaped belt around Jupiter's equator. This signal is caused by cyclotron radiation from electrons that are accelerated in Jupiter's magnetic field.[83]
  • Thermal radiation is produced by heat in the atmosphere of Jupiter.Sony VGP-BPS13/S Battery

Exploration with space probes

Since 1973 a number of automated spacecraft have visited Jupiter, most notably the Pioneer 10 space probe, the first spacecraft to get close enough to Jupiter to send back revelations about the properties and phenomena of the solar system's largest planet.Sony VGP-BPS13A/B Battery

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Entering a Hohmann transfer orbit from Earth to Jupiter from low earth orbit requires a delta-v of 6.3 km/s which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit.Sony VGP-BPS13A/S Battery

Fortunately, gravity assists through planetary flybys can be used to reduce the energy required to reach Jupiter, albeit at the cost of a significantly longer flight duration.[88]

Flyby missions

Beginning in 1973, several spacecraft have performed planetary flyby maneuvers that brought them within observation range of Jupiter. Sony VGP-BPS13AS Battery

The Pioneermissions obtained the first close-up images of Jupiter's atmosphere and several of its moons. They discovered that the radiation fields near the planet were much stronger than expected, but both spacecraft managed to survive in that environment. The trajectories of these spacecraft were used to refine the mass estimates of the Jovian system. Sony VGP-BPS13B/B Battery

Occultations of the radio signals by the planet resulted in better measurements of Jupiter's diameter and the amount of polar flattening.

Six years later, the Voyager missions vastly improved the understanding of the Galilean moons and discovered Jupiter's rings.Sony VGP-BPS13B/Q Battery

They also confirmed that the Great Red Spot was anticyclonic. Comparison of images showed that the Red Spot had changed hue since the Pioneermissions, turning from orange to dark brown. A torus of ionized atoms was discovered along Io's orbital path, and volcanoes were found on the moon's surface, some in the process of erupting. Sony VGP-BPS13B/S Battery

As the spacecraft passed behind the planet, it observed flashes of lightning in the night side atmosphere.

The next mission to encounter Jupiter, the Ulysses solar probe, performed a flyby maneuver to attain a polar orbit around the Sun. During this pass the spacecraft conducted studies on Jupiter's magnetosphere. Sony VGP-BPS13Q Battery

However, since Ulysses has no cameras, no images were taken. A second flyby six years later was at a much greater distance.

In 2000, the Cassini probe, en route to Saturn, flew by Jupiter and provided some of the highest-resolution images ever made of the planet.Sony VGP-BPS13S Battery

On December 19, 2000, the spacecraft captured an image of the moon Himalia, but the resolution was too low to show surface details.

The New Horizons probe, en route to Pluto, flew by Jupiter for gravity assist. Its closest approach was on February 28, 2007.Sony VGP-BPL21 Battery

The probe's cameras measured plasma output from volcanoes on Io and studied all four Galilean moons in detail, as well as making long-distance observations of the outer moons Himalia andElara.[93] Imaging of the Jovian system began September 4, 2006.Sony VGP-BPS21 Battery

Galileo mission

So far the only spacecraft to orbit Jupiter is the Galileo orbiter, which went into orbit around Jupiter on December 7, 1995. It orbited the planet for over seven years, conducting multiple flybys of all the Galilean moons and Amalthea. Sony VGP-BPS21/S Battery

The spacecraft also witnessed the impact of Comet Shoemaker-Levy 9 as it approached Jupiter in 1994, giving a unique vantage point for the event. However, while the information gained about the Jovian system from Galileo was extensive, its originally designed capacity was limited by the failed deployment of its high-gain radio transmitting antenna.[Sony VGP-BPS21A Battery

An atmospheric probe was released from the spacecraft in July 1995, entering the planet's atmosphere on December 7. It parachuted through 150 km of the atmosphere, collected data for 57.6 minutes, and was crushed by the pressure to which it was subjected by that time (about 22 times Earth normal, at a temperature of 153 °C).Sony VGP-BPS21A/B Battery

It would have melted thereafter, and possibly vaporized. The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into the planet on September 21, 2003, at a speed of over 50 km/s, to avoid any possibility of it crashing into and possibly contaminating Europa—a moon which has been hypothesized to have the possibility of harboring life.Sony VGP-BPS21B Battery

Future probes and canceled missions

NASA is planning a mission to study Jupiter in detail from a polar orbit. Named Juno, the spacecraft is planned to launch by 2011.Sony VGP-BPL8 Battery

The Europa Jupiter System Mission (EJSM) is a joint NASA/ESA proposal for exploration of Jupiter and its moons. In February 2009 it was announced that ESA/NASA had given this mission priority ahead of the Titan Saturn System Mission.[99][100] ESA's contribution will still face funding competition from other ESA projects.Sony VGP-BPL8A Battery

Launch date will be around 2020. EJSM consists of the NASA-led Jupiter Europa Orbiter, and the ESA-led Jupiter Ganymede Orbiter.[102]

Because of the possibility of subsurface liquid oceans on Jupiter's moons Europa, Ganymede and Callisto, there has been great interest in studying the icy moons in detail. Funding difficulties have delayed progress. Sony VGP-BPL8B Battery

NASA's JIMO (Jupiter Icy Moons Orbiter) was cancelled in 2005.[103] A European Jovian Europa Orbiter mission was also studied.[104]These missions were superseded by the Europa Jupiter System Mission (EJSM).Sony VGP-BPS8 Battery


Jupiter has 64 named natural satellites. Of these, 47 are less than 10 kilometres in diameter and have only been discovered since 1975. The four largest moons, known as the "Galilean moons", are Io, Europa, Ganymede and Callisto.Sony VGP-BPS8A Battery

Galilean moons

The orbits of Io, Europa, and Ganymede, some of the largest satellites in the Solar System, form a pattern known as a Laplace resonance; for every four orbits that Io makes around Jupiter, Europa makes exactly two orbits and Ganymede makes exactly one.Sony VGP-BPS8B Battery

This resonance causes the gravitational effects of the three large moons to distort their orbits into elliptical shapes, since each moon receives an extra tug from its neighbors at the same point in every orbit it makes. The tidal force from Jupiter, on the other hand, works to circularize their orbits.HP Compaq Business 6910p Battery

The eccentricity of their orbits causes regular flexing of the three moons' shapes, with Jupiter's gravity stretching them out as they approach it and allowing them to spring back to more spherical shapes as they swing away. This tidal flexing heats the moons' interiors by friction. Panasonic LUMIX DMC-TZ4S Battery

This is seen most dramatically in the extraordinary volcanic activity of innermost Io (which is subject to the strongest tidal forces), and to a lesser degree in the geological youth of Europa's surface (indicating recent resurfacing of the moon's exterior).Sony NP-FH100 Battery

Classification of moons

Before the discoveries of the Voyager missions, Jupiter's moons were arranged neatly into four groups of four, based on commonality of their orbital elements. Since then, the large number of new small outer moons has complicated this picture. There are now thought to be six main groups, although some are more distinct than others.Toshiba Equium M50-192 Battery

A basic sub-division is a grouping of the eight inner regular moons, which have nearly circular orbits near the plane of Jupiter's equator and are believed to have formed with Jupiter. The remainder of the moons consist of an unknown number of small irregular moons with elliptical and inclined orbits, Apple MacBook Pro Battery

which are believed to be captured asteroids or fragments of captured asteroids. Irregular moons that belong to a group share similar orbital elements and thus may have a common origin, perhaps as a larger moon or captured body that broke up.Apple PowerBook G4 Battery

Interaction with the Solar System

Along with the Sun, the gravitational influence of Jupiter has helped shape the Solar System. The orbits of most of the system's planets lie closer to Jupiter's orbital plane than the Sun's equatorial plane(Mercury is the only planet that is closer to the Sun's equator in orbital tilt),Acer BATBL50L6 Battery

the Kirkwood gaps in the asteroid belt are mostly caused by Jupiter, and the planet may have been responsible for the Late Heavy Bombardment of the inner Solar System's history.

Along with its moons, Jupiter's gravitational field controls numerous asteroids that have settled into the regions of the Lagrangian points preceding and following Jupiter in its orbit around the sun. Canon EOS 450D Battery

These are known as the Trojan asteroids, and are divided into Greek and Trojan "camps" to commemorate theIliad. The first of these, 588 Achilles, was discovered by Max Wolf in 1906; since then more than two thousand have been discovered.[110] The largest is 624 Hektor.Dell 451-10617 battery

Most short-period comets belong to the Jupiter family—defined as comets with semi-major axes smaller than Jupiter's. Jupiter family comets are believed to form in the Kuiper belt outside the orbit of Neptune. During close encounters with Jupiter their orbits are perturbed into a smaller period and then circularized by regular gravitational interaction with the Sun and Jupiter.Acer Travelmate 2400 Battery


Jupiter has been called the Solar System's vacuum cleaner,[113] because of its immense gravity well and location near the inner Solar System. It receives the most frequent comet impacts of the Solar System's planets.Dell Inspiron 1525 Adapter

It was thought that the planet served to partially shield the inner system from cometary bombardment. However, recent computer simulations suggest that Jupiter does not cause a net decrease in the number of comets that pass through the inner Solar System, as its gravity perturbs their orbits inward in roughly the same numbers that it accretes or ejects them.[Compaq Presario 2100 Adapter

This topic remains controversial among astronomers, as some believe it draws comets towards Earth from the Kuiper belt while others believe that Jupiter protects Earth from the alleged Oort cloud.

A 1997 survey of historical astronomical drawings suggested that the astronomer Cassini may have recorded an impact scar in 1690.Acer Aspire 1362 Battery

The survey determined eight other candidate observations had low or no possibilities of an impact.[117] During the period July 16, 1994, to July 22, 1994, over 20 fragments from thecomet Shoemaker-Levy 9 (SL9, formally designated D/1993 F2) collided with Jupiter's southern hemisphere,Toshiba Equium M50-192 Battery

providing the first direct observation of a collision between two Solar System objects. This impact provided useful data on the composition of Jupiter's atmosphere.

On July 19, 2009, an impact site was discovered at approximately 216 degrees longitude in System 2.Dell XPS M1330 Battery

This impact left behind a black spot in Jupiter's atmosphere, similar in size to Oval BA. Infrared observation showed a bright spot where the impact took place, meaning the impact warmed up the lower atmosphere in the area near Jupiter's south pole.Acer Travelmate 2200 Adapter

Another impact event, smaller than the previous observed impacts, was detected on June 3, 2010, by Anthony Wesley, an amateur astronomer in Australia, and was later discovered to have been captured on video by another amateur astronomer in the Philippines.HP Compaq 6735b Adapter

Possibility of life

In 1953, the Miller–Urey experiment demonstrated that a combination of lightning and the chemical compounds that existed in the atmosphere of a primordial Earth could form organic comp

ounds (including amino acids) that could serve as the building blocks of life.Dell Vostro 1000 Battery

The simulated atmosphere included water, methane, ammonia and molecular hydrogen; all molecules still found in the atmosphere of Jupiter. However, the atmosphere of Jupiter has a strong vertical air circulation, which would carry these compounds down into the lower regions. HP Compaq nx7300 Adapter

The higher temperatures within the interior of the atmosphere breaks down these chemicals, which would hinder the formation of Earth-like life.

It is considered highly unlikely that there is any Earth-like life on Jupiter, as there is only a small amount of water in the atmosphere and any possible solid surface deep within Jupiter would be under extraordinary pressures.Asus f82 Battery

However, in 1976, before the Voyager missions, it was hypothesized that ammonia or water-based life could evolve in Jupiter's upper atmosphere. This hypothesis is based on the ecology of terrestrial seas which have simple photosynthetic plankton at the top level, fish at lower levels feeding on these creatures, and marine predators which hunt the fish.Dell XPS M1330 Battery

The possible presence of underground oceans on some of Jupiter's moons has led to speculation that the presence of life is more likely there.

Ancient mythology

The planet Jupiter has been known since ancient times. HP Compaq Business 6910p Battery

It is visible to the naked eye in the night sky and can occasionally be seen in the daytime when the sun is low.[127] To the Babylonians, this object represented their god Marduk. They used the roughly 12-year orbit of this planet along the ecliptic to define the constellations of their zodiac.Compaq PRESARIO R3000 Battery

The Romans named it after Jupiter (Latin: Iuppiter, I?piter) (also called Jove), the principal god of Roman mythology, whose name comes from the Proto-Indo-European vocative compound *Dy?u-p?ter(nominative: *Dy?us-p?t?r, meaning "O Father Sky-God", or "O Father Day-God").HP Compaq Business NX6110 Battery

The astronomical symbol for the planet, ?, is a stylized representation of the god's lightning bolt. The original Greek deity, Zeus, adopted by Romans, supplies the root zeno-, used to form some Jupiter-related words, such as zenographic.Dell Latitude D610 Adapter

Jovian is the adjectival form of Jupiter. The older adjectival form jovial, employed by astrologers in the Middle Ages, has come to mean "happy" or "merry," moods ascribed to Jupiter's astrological influence.

The Chinese, Korean and Japanese referred to the planet as the wood star, Chinese: ??; pinyin: mùx?ng, based on the Chinese Five Elements.Asus Eee PC 701 Adapter

The Greeks called it ??????, Phaethon, "blazing." In Vedic Astrology, Hindu astrologers named the planet after Brihaspati, the religious teacher of the gods, and often called it "Guru", which literally means the "Heavy One."[134] In the English language,Thursday is derived from "Thor's day", with Thor associated with the planet Jupiter in Germanic mythology.HP Compaq Business NX6325 Battery

The exploration of Jupiter has to date been conducted via close observations by automated spacecraft. It began with the arrival of Pioneer 10 into the Jovian system in 1973, and, as of 2008, has continued with seven further spacecraft missions.Dell Studio XPS 16 Battery

All of these missions were undertaken by NASA, and all save one have been flybys that take detailed observations without the probe landing or entering orbit. These probes make Jupiter the most visited of the Solar System'souter planets. Plans for more missions to the Jovian system are under development, none of which are scheduled to arrive at the planet before 2016.Acer Aspire 5520 Battery

Sending a craft to Jupiter entails many technical difficulties, especially due to the probes' large fuel requirements and the effects of the planet's harsh radiation environment.

The first spacecraft to visit Jupiter was Pioneer 10 in 1973, followed a few months later by Pioneer 11. Acer TravelMate 5720 Adapter

Aside from taking the first close-up pictures of the planet, the probes discovered its magnetosphere and its largely fluid interior. The Voyager 1 and Voyager 2 probes visited the planet in 1979, and studied itsmoon and the ring system, discovering the volcanic activity of Io and the presence of water ice on the surface of Europa. HP Compaq 6735s Adapter

Ulysses further studied Jupiter's magnetosphere in 1992 and then again in 2000. The Cassini probe approached the planet in 2000 and took very detailed images of its atmosphere. The New Horizons spacecraft passed by Jupiter in 2007 and made improved measurements of its and its satellites' parameters.Dell XPS M1330 Battery

The Galileo spacecraft is the only one to have actually entered an orbit around Jupiter, arriving in 1995 and studying the planet until 2003. During this periodGalileo gathered a large amount of information about the Jovian system, making close approaches to all of the four giant Galilean moons and finding evidence for thin atmospheres on three of them, HP Compaq nc6230 Adapter

as well as the possibility of liquid water beneath their surfaces. It also discovered a magnetic field around Ganymede. As it approached Jupiter, it also witnessed the impact of Comet Shoemaker-Levy 9. In December 1995, it sent an atmospheric probe into the Jovian atmosphere, so far the only craft to do so.Dell T117C Battery

Future probes planned by NASA include the Juno spacecraft, due to launch in 2011, which will enter a polar orbit around Jupiter to determine whether it possesses a rocky core, and the Europa Jupiter System Mission, due to launch sometime around 2020, which will engage in an extended study of the planets moon system, particularly Europa and Ganymede, Asus x5dij-sx039c Battery

and settle the long-running scientific debate over whether an ocean of liquid water exists under Europa's icy surface. Some NASA administrators have even speculated as to the possibility of manned exploration of Jupiter, but such missions are not considered feasible with current technology.Dell Inspiron 1464 Battery

Technical requirements

Flights from Earth to other planets in the Solar System have a high energy cost. It requires almost the same amount of energy for a spacecraft to reach Jupiter from Earth's orbit as it does to lift it into orbit in the first place. In astrodynamics, this energy expenditure is defined by the net change in the spacecraft's velocity, or delta-V. HP Compaq 6720s Adapter

The energy needed to reach Jupiter from an Earth orbit requires a delta-V of about 9 km/s,[1] compared to the 9.0–9.5 km/s to reach a low Earth orbit from the ground.[2] However, gravity assists through planetary flybys (such as by Earth or Venus) can be used to reduce the energetic requirement (i.e., the fuel) at launch, Dell Latitude D630 Adapter

albeit at the cost of a significantly longer flight duration to reach a target such as Jupiter when compared to the direct trajectory.[3]Ion thrusters capable of a delta v of more than 10 kilometers/s were used on the Dawn spacecraft.[4] This is more than enough delta v to do a Jupiter fly-by mission from a solar orbit of the same radius as earth's orbit without gravity assist.HP Pavilion dm4 Battery

A major problem in sending space probes to Jupiter is that the planet has no solid surface on which to land, as there is a smooth transition between the planet's atmosphereand its fluid interior. Any probes descending into the atmosphere are eventually crushed by the immense pressures within Jupiter.[6]Sony NP-FS11 Battery

Another major issue is the amount of radiation to which a space probe is subjected, due to the harsh charged-particle environment around Jupiter (for a detailed explanation seeMagnetosphere of Jupiter). For example, when Pioneer 11 made its closest approach to the planet, Dell Inspiron 1520 Adapter

the level of radiation was ten times more powerful than Pioneer's designers had predicted, leading to fears that the probes would not survive; however, with a few minor glitches, the probe managed to pass through the radiation belts. It did however lose most of the images of the moon Io, as the radiation had caused Pioneer's imaging photo polarimeter to receive a number of false commands.Toshiba PA3399U-1BRS Battery

The subsequent and far more technologically advancedVoyager spacecraft had to be redesigned to cope with the massive radiation levels.[8] The Galileo spacecraft, over the eight years it orbited the planet, the probe's radiation dose far exceeded its design specifications, and its systems failed on several occasions. Acer Aspire 5920G Adapter

The spacecraft's gyroscopes often exhibited increased errors, and electrical arcs sometimes occurred between its rotating and non-rotating parts, causing it to enter safe mode, which led to total loss of the data from the 16th, 18th and 33rd orbits. The radiation also caused phase shifts in Galileo's ultra-stable quartz oscillator.Acer Aspire 5920 Battery

Pioneer program (1973 and 1974)

The first spacecraft to explore Jupiter was Pioneer 10, which flew past the planet in December 1973, followed by Pioneer 11 thirteen months later. Pioneer 10obtained the first-ever close-up images of Jupiter and its Galilean moons; IBM Thinkpad T40 Adapter

the spacecraft studied the planet's atmosphere, detected its magnetic field, observed its radiation belts and determined that Jupiter is mainly fluid. Pioneer 11 made its closest approach, within some 34,000 km of Jupiter's cloud tops, on December 4, 1974. It obtained dramatic images of the Great Red Spot,Nikon COOLPIX 4300 Battery

made the first observation of Jupiter's immense polar regions, and determined the mass of Jupiter's moon Callisto. The information gathered by these two spacecraft helped astronomers and engineers improve the design of future probes to cope more effectively with the environment around the giant planet.Apple MB771 Battery

Voyager program (1979)

Voyager 1 began photographing Jupiter in January 1979 and made its closest approach on March 5, 1979, at a distance of 349,000 km from Jupiter's center. This close approach allowed for greater image resolution, though the flyby's short duration meant that most observations of Jupiter's moons, Sony DSC-P5 Battery

rings, magnetic field, and radiation environment were made in the 48-hour period bracketing the approach, even though Voyager 1continued photographing the planet until April. It was soon followed by Voyager 2, which made its closest approach on July 9, 1979,[14] 576 million km away from the planet's cloud tops.Dell Inspiron 6400 Adapter

The probe discovered Jupiter's ring, observed intricate vortices in its atmosphere, observed active volcanoes on Io, a process analogous to plate tectonics on Ganymede, and numerous craters on Callisto.

The Voyager missions vastly improved our understanding of the Galilean moons, and also discovered Jupiter's rings.Toshiba PA3534U-1BRS Battery

They also took the first close up images of the planet's atmosphere, revealing the Great Red Spot as a complex storm moving in a counter-clockwise direction. An array of other smaller storms and eddies were found throughout the banded clouds (see animation on the right).[Sony NP-FP50 Battery

Two new, small satellites, Adrastea and Metis, were discovered orbiting just outside the ring, making them the first of Jupiter's moons to be identified by a spacecraft.[18][19] A third new satellite, Thebe, was discovered between the orbits of Amalthea and Io.HP Compaq nx7300 Adapter

The discovery of volcanic activity on the moon Io was the greatest unexpected finding of the mission, as it was the first time an active volcano was observed on a celestial body other than Earth. Together, the Voyagers recorded the eruption of nine volcanoes on Io, as well as evidence for other eruptions occurring between the Voyager encounters.Dell Latitude D820 Adapter

Europa displayed a large number of intersecting linear features in the low-resolution photos from Voyager 1. At first, scientists believed the features might be deep cracks, caused by crustal rifting or tectonic processes. However, the high-resolution photos from Voyager 2, taken closer to Jupiter, Toshiba PA3399U-1BRS Battery

left scientists puzzled as the features in these photos were almost entirely lacking in topographic relief. This led many to suggest that these cracks might be similar to ice floes on Earth, and that Europa might have a liquid water interior. Europa may be internally active due to tidal heating at a level about one-tenth that of Io, Dell Studio XPS 1640 Battery

and as a result, the moon is thought to have a thin crust less than 30 kilometers (18 miles) thick of water ice, possibly floating on a 50-kilometers-deep (30 mile) ocean.

Ulysses (1992)

On February 8, 1992, the Ulysses solar probe flew past Jupiter's north pole at a distance of 451,000 km.Dell Latitude D830 Battery

This swing-by maneuver was required for Ulysses to attain a very high-inclination orbit around the Sun, increasing its inclination to the ecliptic to 80.2 degrees.  The giant planet's gravity bent the spacecraft's flightpath downward and away from the ecliptic plane, placing it into a final orbit around the Sun's north and south poles. Dell Inspiron E1505 Adapter

The size and shape of the probe's orbit were adjusted to a much smaller degree, so that its aphelion remained at approximately 5 AU (Jupiter's distance from the Sun), while its perihelion lay somewhat beyond 1 AU (Earth's distance from the Sun). During its Jupiter encounter, the probe made measurements of the planet's magnetosphere.Asus Eee PC 1201PN Battery

Since the probe had no cameras, no images were taken. In February 2004, the probe arrived again at the vicinity of Jupiter. This time the distance from the planet was much greater—about 240 million km—but it made further observations of Jupiter. Asus Eee PC 701 Adapter

Cassini (2000)

In 2000, the Cassini probe, en route to Saturn, flew by Jupiter and provided some of the highest-resolution images ever taken of the planet. It made its closest approach on December 30, 2000, and made many scientific measurements. About 26,000 images of Jupiter were taken during the months-long flyby. Dell XPS M1330 Battery

It produced the most detailed global color portrait of Jupiter yet, in which the smallest visible features are approximately 60 km (40 miles) across.

A major finding of the flyby, announced on March 6, 2003, was of Jupiter's atmospheric circulation. fujifilm np95 Battery

Dark belts alternate with light zones in the atmosphere, and the zones, with their pale clouds, had previously been considered by scientists to be areas of upwelling air, partly because on Earth clouds tend to be formed by rising air. But analysis of Cassini imagery showed that the dark belts contain individual storm cells of upwelling bright-white clouds, Asus Eee PC 900 Adapter

too small to see from Earth. Anthony Del Genio of NASA's Goddard Institute for Space Studies said that "the belts must be the areas of net-rising atmospheric motion on Jupiter, [so] the net motion in the zones has to be sinking".

Other atmospheric observations included a swirling dark oval of high atmospheric-haze, about the size of the Great Red Spot, near Jupiter's north pole.Sony VAIO PCG-713 Battery

Infrared imagery revealed aspects of circulation near the poles, with bands of globe-encircling winds, with adjacent bands moving in opposite directions. The same announcement also discussed the nature of Jupiter's rings. Light scattering by particles in the rings showed the particles were irregularly shaped (rather than spherical) Dell Latitude D830 Adapter

and likely originated as ejecta from micrometeorite impacts on Jupiter's moons, probably on Metis and Adrastea. On December 19, 2000, theCassini spacecraft captured a very low resolution image of the moon Himalia, but it was too distant to show any surface details.Dell Studio XPS 1640 Battery

New Horizons (2007)

The New Horizons probe, en route to Pluto, flew by Jupiter for a gravity assist and was the first probe launched directly towards Jupiter since the Ulysses in 1990. Its Long Range Reconnaissance Imager (LORRI) took its first photographs of Jupiter on September 4, 2006.Panasonic LUMIX DMC-TZ4S  Battery

The spacecraft began further study of the Jovian system in December 2006, and made its closest approach on February 28, 2007.

While close to Jupiter, New Horizons' instruments made refined measurements of the orbits of Jupiter's inner moons, particularly Amalthea. HP Compaq Business NX6320 Battery

The probe's cameras measured volcanoes on Io, studied all four Galilean moons in detail, and made long-distance studies of the outer moons Himalia and Elara.[34] The craft also studied Jupiter's Little Red Spot and the planet's magnetosphere and tenuous ring system.Canon POWERSHOT G2 Battery

On March 19, 2007 the Command and Data Handling computer experienced an uncorrectable memory error and rebooted itself, causing the spacecraft to go into safe mode. The craft fully recovered within two days, with some data loss on Jupiter's magnetotail. No other data loss events were associated with the encounter.Dell Latitude E6500 Battery

Galileo orbital mission (1995–2003)

So far, the only spacecraft to orbit Jupiter is the Galileo orbiter, which went into orbit around Jupiter on December 7, 1995. It orbited the planet for over seven years, making 35 orbits before it was destroyed during a controlled impact with Jupiter on September 21, 2003.Dell LATITUDE D630 Battery

During this period it gathered a large amount of information about the Jovian system, although the amount of information was not as great as intended because the deployment of its high-gain radio transmitting antenna failed. The major events during the eight-year study included multiple flybys of all of the Galilean moons, as well as Amalthea (the first probe to do so).Asus R33030 Adapter

It also witnessed the impact of Comet Shoemaker-Levy 9 as it approached Jupiter in 1994 and the sending of an atmospheric probe into the Jovian atmosphere in December 1995.

Cameras on the Galileo spacecraft observed fragments of the Shoemaker-Levy 9 comet between July 16 and July 22, 1994 as they collided with Jupiter's southern hemisphere at a speed of approximately 60 kilometres per secondDell Mini 1011 Battery

. This was the first direct observation of an extraterrestrial collision of solar system objects.[40] While the impacts took place on the side of Jupiter hidden from Earth, Galileo, then at a distance of 1.6 AU from the planet, was able to see the impacts as they occurred. Its instruments detected a fireball which reached a peak temperature of about 24,000 K,toshiba pa3332u-1brs Battery

compared to the typical Jovian cloudtop temperature of about 130 K, with the plume from the fireball reaching a height of over 3,000 km.[41]

An atmospheric probe was released from the spacecraft in July, 1995, entering the planet's atmosphere on December 7, 1995. HP Compaq 6710b Adapter

After a high-g descent into the Jovian atmosphere, the probe discarded the remains of its heat shield, and it parachuted through 150 km of the atmosphere, collecting data for 57.6 minutes, before being crushed by the pressure and temperature to which it was subjected (about 22 times Earth normal, at a temperature of 153 °C).HP Compaq nx6325 Adapter

It would have melted thereafter, and possibly vaporized. The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into the planet on September 21, 2003 at a speed of over 50 km/s,[37] in order to avoid any possibility of it crashing into and contaminating Europa.Acer Aspire 5720 Adapter

Major scientific results of the Galileo mission include:

  • the first observation of ammonia clouds in another planet's atmosphere—the atmosphere creates ammonia ice particles from material coming up from lower depths;Toshiba Equium A110-252 Battery
  • confirmation of extensive volcanic activity on Io—which is 100 times greater than that found on Earth; the heat and frequency of eruptions are reminiscent of early Earth;
  • observation of complex plasma interactions in Io's atmosphere which create immense electrical currents that couple to Jupiter's atmosphere;Acer Aspire 5052ANWXMi Battery
  • providing evidence for supporting the theory that liquid oceans exist under Europa's icy surface;
  • first detection of a substantial magnetic field around a satellite (Ganymede);
  • magnetic data evidence suggesting that Europa, Ganymede and Callisto have a liquid-saltwater layer under the visible surface;Dell Mini 1011v Battery
  • evidence for a thin atmospheric layer on Europa, Ganymede, and Callisto known as a 'surface-bound exosphere';
  • understanding of the formation of the rings of Jupiter (by dust kicked up as interplanetary meteoroids which smash into the planet's four small inner moons) and observation of two outer rings and the possibility of a separate ring along Amalthea's orbit;HP Compaq nx7300 Adapter
  • identification of the global structure and dynamics of a giant planet's magnetosphere.

Proposed missions

NASA is planning a mission to study Jupiter in detail from a polar orbit. Named Juno, the spacecraft is planned to launch in August 2011.Dell Vostro 1510 Battery

The spacecraft will be placed in a polar orbit to study theplanet's composition, gravity field, magnetic field, and polar magnetosphere. Juno will also search for clues about how Jupiter formed, including whether the planet has a rocky core, the amount of water present within the deep atmosphere, and how the mass is distributed within the planet. Toshiba PA3534U-1BRS Battery

Juno will also study Jupiter's deep winds,[ which can reach speeds of 600 km/h.

The Europa Jupiter System Mission (EJSM) is a joint NASA/ESA proposal for exploration of Jupiter and its moons. In February 2009 it was announced that ESA/NASA had given this mission priority ahead of the Titan Saturn System Mission.Asus M50 Battery

The proposal includes a launch date of around 2020 and consists of the NASA-led Jupiter Europa Orbiter, and the ESA-led Jupiter Ganymede Orbiter. ESA's contribution will still face funding competition from other ESA projects.Asus Eee PC 901 Battery

Cancelled missions

Because of the possibility of subsurface liquid oceans on Jupiter's moons Europa, Ganymede and Callisto, there has been great interest in studying the icy moons in detail. Funding difficulties have delayed progress. The Europa Orbiter was a planned NASA mission to Europa, which was canceled in 2002.Dell Inspiron 6400 Battery

Its main objectives included determining the presence or absence of a subsurface ocean and identifying candidate sites for future lander missions. Then there was NASA's JIMO (Jupiter Icy Moons Orbiter) that was canceled in 2005.[61] A European Jovian Europa Orbiter mission was also studied.HP Compaq Business NC6220 Battery

These missions were superseded by the Europa Jupiter System Mission (EJSM) described above.

Manned exploration

While it is not possible to land on Jupiter itself, it is possible to land on the Galilean moons, leading to the possibility of future manned exploration.Sony VGP-BPS9 Battery

Particular targets are Europa, due to its potential for life, and Callisto, due to its relatively low radiation dose.In 2003, NASA proposed a program called Human Outer Planets Exploration (HOPE) that involved a manned mission to the Galilean moons.[65]NASA has projected a possible attempt some time in the 2040s.Sony VGP-BPS13 Battery

In the Vision for Space Exploration policy announced in January 2004, NASA has discussed manned missions beyond Mars, mentioning that a "human research presence" may be desirable on Jupiter's moons.  Before the JIMO mission was cancelled, NASA administrator Sean O'Keefe stated that "human explorers will follow."HP Compaq nx7300 Adapter

Potential for colonization

NASA has speculated on the feasibility of mining the atmospheres of the outer planets, particularly for helium-3, an isotope of helium rare on Earth, but highly desired in nuclear fusion research. Factories stationed in orbit could mine the gas and deliver it to visiting craft.HP Compaq 2510p Adapter

However, the Jovian system in general poses particular disadvantages for colonizing because of its severe radiation environment and its particularly deep gravity well. Its radiation would deliver about 36 Sv (3600 rem) per day to unshielded colonists at Io and about 5.4 Sv (540 rems) per day to unshielded colonists atEuropa.Dell Studio PP39L Battery

Exposure of approximately .75 Sv over a period of a few days is enough to cause radiation poisoning, and about 5 Sv over a few days is fatal.

Ganymede is the largest moon in the Solar System. Ganymede is the only moon with a magnetosphere but it is overshadowed by Jupiter's magnetic field. Nikon COOLPIX 5700  Battery

Ganymede receives about 0.08 Sv (8 rem) of radiation per day. Callisto being further from Jupiter's powerful radiation belt is subject to 0.0001 Sv (0.01 rem) a day.For comparison, the average amount of radiation taken on Earth by a living organism is about 0.024 Sv per year; Dell Studio XPS 16 Battery

the highest natural radiation levels on Earth are recorded around Ramsar hot springs at about 0.26 Sv per year.

One of the main targets chosen by the HOPE study was Callisto. The possibility was mooted of building a surface base on Callisto, because of the low radiation levels at the moon's distance from Jupiter and its geological stability.HP Compaq nx7400 Adapter

Callisto is the only one of Jupiter's Galilean satellites for which human exploration is feasible. The levels of ionizing radiation on Io, Europa and Ganymede are hostile to human life, and adequate protective measures have yet to be devised.HP Pavilion DV6500 Adapter

It could be possible to build a surface base that would produce fuel for further exploration of the solar system. In 1997, the Artemis Project designed a plan to colonize Europa.[64]According to the plan, explorers would drill down into the Europan ice crust, entering the postulated subsurface ocean, where they would inhabit artificial air pockets.Dell T117C Battery

Pioneer 10 (also known as Pioneer F) is a 258-kilogram robotic space probe launched by NASA on March 2, 1972 to study the asteroid belt, the environment around Jupiter, solar wind, cosmic rays, and eventually the far reaches of the solar system and heliosphere.Acer PA-1650-02 Adapter

It was the first spacecraft to traverse the asteroid belt and the first to encounter Jupiter. Because of power constraints and the vast distance of the probe, communication has been lost since January 23, 2003.


In the 1960s, American aerospace engineer Gary Flandro of the NASA Jet Propulsion Laboratory conceived of a mission, known as the Planetary Grand Tour, that would exploit a rare alignment of the outer planets of the Solar System. Acer Aspire 5920G Adapter

To prepare for this mission, in 1964 NASA decided to launch a pair of probes to the outer Solar System.[2] An advocacy group, led by American space scientist James A. Van Allen, worked out the scientific rationale for exploring the outer planets.[3] Goddard put together a proposal for a pair of "Galactic Jupiter Probes" that would pass through the asteroid belt and visit Jupiter during a thirteen month window in 1972 and 1973. Asus S1 Adapter

Approved in February 1969,[4] the twin spacecraft designated Pioneer F and Pioneer G formed part of the Pioneer program,[5] a series of United States unmanned space missions launched between 1958 and 1978. This model was the first in the series to be designed for exploring the outer solar system. HP Pavilion dv6000 Battery

Yielding to multiple proposals throughout the 1960s, early mission objectives were defined as:

  • Explore the interplanetary medium beyond the orbit of Mars
  • Investigate the nature of the asteroid belt from the scientific standpoint and assess the belt's possible hazard to missions to the outer planets.
  • Explore the environment of Jupiter. Ibm Thinkpad T30 Battery

Later development-stage objectives also included the probe closely approaching Jupiter to provide data on the effect the environmental radiation surrounding Jupiter would have to the instruments on the spacecraft.Dell Studio PP39L Battery

NASA Ames Research Center, rather than Goddard, was selected to manage the project as part of the Pioneer program.[4] In February 1970, Ames awarded a combined $380 million contract to TRW for building both the Pioneer 10 and Pioneer 11 vehicles, bypassing the bidding process to save time.HP Pavilion dv5 Adapter

The TRW team that assembled the spacecraft were led by B. J. O'Brien and Herb Lassen.[6] Design and construction of the spacecraft required an estimated 25 million man-hours.[7]

A backup unit, Pioneer H, is currently on display in the "Milestones of Flight" exhibit at the National Air and Space Museum in Washington, D.C..[8] Many elements of the mission proved to be critical in the planning of the Voyager Program[9]:266-8.HP Compaq Business NC6400 Battery

Pioneer plaque

Pioneer 10 and Pioneer 11 carry a gold-anodized aluminium plaque in the event that either spacecraft is ever found by intelligent life-forms from other planetary systems. The plaques feature the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft.HP Compaq 490306-001 Battery

Spacecraft design

The Pioneer 10 bus measures 36-centimeters deep and with six 76-centimeters long panels forming the hexagonal structure. The bus houses propellant to control the orientation of the probe and eight of the eleven scientific instruments. Compaq Presario CQ35-100 Battery

The equipment compartment lies within an aluminum honeycomb structure to provide protection from meteoroids. A layer of insulation provided passive thermal control. At launch, the spacecraft carried 36 kg of hydrazine propellant in a 42 cm diameter spherical tank.[11] The spacecraft had a mass of 260-kilograms.[HP Compaq HSTNN-LB51 Battery

Attitude control and propulsion

Orientation of the spacecraft was maintained with six 4.5 N,  hydrazine monopropellant thrusters: pair one maintained a constant spin-rate of 4.8-rpm, pair two controlled the forward thrust, pair three controlled attitude. Information for the orientation was provided by a star sensor able to reference Canopus, and two sun sensors.HP Pavilion ZE4500 Battery


The space probe included a redundant system of transceivers, one attached to the high-gain antenna, the other to an omni-antenna and medium-gain antenna. Each transceiver is 8 watts and transmits data across the S-band using 2110 MHz for the uplink from Earth and 2292 MHz for the downlink to Earth with the Deep Space Network tracking the signal.HP G62-100EB Battery
Prior to transmitting data, used a convolutional encoder, a form of error correction, to avoid sending corrupted data.[1]:43


Pioneer 10 used 4 SNAP-19 radioisotope thermoelectric generators (RTG) (see diagram). They were positioned on 2 three-rod trusses, each 3 meters (10 feet) in length and 120 degrees apart.HP Pavilion DV6-1211AX Battery
This was expected to be a safe distance from the sensitive scientific experiments carried on board. Combined, the RTGs provided 155 watts at launch, and decayed to 140 W in transit to Jupiter. The spacecraft required 100 W to power all systems.HP Pavilion DV6-1220SO Battery
The generators were powered by the radioisotope fuel plutonium-238, which was housed in a multi-layer capsule protected by a graphite heat shield.[13] The pre-launch requirement for the SNAP-19 was to provide power for two years in space; this was greatly exceeded during the actual mission.HP EliteBook 6930P Battery


Much of the computation for the mission was performed on Earth and transmitted to the probe, where it was able to retain in memory, up to five commands of the 222 possible entries by ground controllers. HP Pavilion DV6-1210SA Battery
The spacecraft included two command decoders and a command distribution unit, a very limited form of processor, to direct operations on the spacecraft. This system required that mission operators prepare commands long in advance of transmitting them to the probe. Compaq Presario CQ71 Battery
A data storage unit was included to record up to 6,144-bytes of information gathered by the instruments. The digital telemetry unit would then be used to prepare the collected data in one of the thirteen possible formats before transmitting it back to Earth.HP Pavilion DV7-1290EO Battery

Launch and trajectory

The Pioneer 10 probe was launched on March 3, 1972 at 01:49:00 UTC (March 2 local time) by the National Aeronautics and Space Administration from Space Launch Complex 36A at Cape Canaveral, Florida aboard an Atlas/Centaur launch vehicle. HP G6000 Battery

The third stage consisted of a solid fuel TE364-4 developed specifically for the Pioneer missions. This stage provided about 15,000 pounds of thrust and spun up the spacecraft. The spacecraft had an initial spin rate of 30 revolutions per minute. Twenty minutes following the launch, the vehicle's three booms were extended, which slowed the rotation rate to 4.8 per minute. HP HDX X18-1005EA Battery

This rate was maintained throughout the voyage. The launch vehicle accelerated the probe for net interval of 17 minutes, reaching a velocity of 51,682 kilometers/hour (32,114 miles/hour).

After contacting the high-gain antenna, several of the instruments were activated for testing while Pioneer 10 was moving through the Earth's radiation belts. HP Pavilion DV6-3013SL Battery

Ninety minutes after launch, the spacecraft reached interplanetary space.[34] Pioneer 10 passed by the moon in 11 hours and become the fastest man-made object at that time. During the first seven months of the journey, the spacecraft made three course corrections.HP Compaq HSTNN-IB62 Battery

The on-board instruments underwent checkouts, with the photometers examining Jupiter and the Zodiacal light, and experiment packages being used to measure cosmic rays, magnetic fields and the solar wind. The only anomaly during this interval was the failure of the star sensor, which instead required the spacecraft to maintain its orientation using the sun sensor.HP Pavilion DV6100 Battery

After March 31, 1997, Pioneer 10's weak signal continued to be tracked by the Deep Space Network to aid the training of flight controllers in the process of acquiring deep space radio signals. There was an Advanced Concepts study applying chaos theory to extract coherent data from the fading signal.HP EliteBook 2730P Battery

The last successful reception of telemetry was received from Pioneer 10 on April 27, 2002; subsequent signals were barely strong enough to detect, and provided no usable data. The final, very weak signal from Pioneer 10 was received on January 23, 2003 when it was 12 billion-kilometers (80 AU) from Earth.HP Pavilion DV9000 Battery

Further attempts to contact the spacecraft were unsuccessful. The final attempt was made on the evening of March 4, 2006, the last time the antenna would be correctly aligned with Earth. No response was received from Pioneer 10.[38] Loss of contact was probably due to a combination of increasing distance and the steadily weakening power source on the spacecraft.HP Pavilion DV7 Battery

As of April 1, 2011, Pioneer 10 is approximately 103.017 AU from the Sun. It is at an elliptic latitude of 3 degrees, at a declination of 25.83 degrees. It is traveling at about 12.061 km/s and is traveling outward at about 2.544 AU a year. Pioneer 10 is at a right ascension of 5.077 hours. Sunlight takes 14.32 hours to get to Pioneer 10 at its approximate distance. HP Pavilion DV7-1290EO Battery

Pioneer 10 is traveling in the opposite direction when compared to Voyager 1, Voyager 2 , Pioneer 11, and New Horizons. The spacecraft distance and measurements are only true guesses due to no communication with the probe.HP Compaq Business 6735S Battery

Space is a vacuum and as long as the spacecraft does not intercept anything, it should be about the same in terms of latitude and other longitude and latitude directions. If left undisturbed, Pioneer 10 will join the Voyager Spacecraft and will leave the solar system to wander interstellar space. HP 540 Battery

All numbers are guesses based on the last communication and on where it should be at its estimated speed. Pioneer 10 is believed to possibly still be transmitting extremely weak signals, however its antenna is not oriented to the earth, and therefore no signals can be detected. HP Compaq Business NW9440 Battery

NASA has no further intentions or plans in the future to communicate with Pioneer 10, if it is not already completely dead. 12 km/s is still fast enough for solar escape.

Pioneer 10 is heading in the direction of the star Aldebaran in the constellation Taurus at approximately 2.6 AU per year. HP Compaq Business  TC4400 Battery

If Aldebaran had zero relative velocity, it would take Pioneer 10 approximately 2 million years to reach the star.HP Compaq 491278-001 Battery,HP P

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