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The Jupiter Portal


Astronomical symbol of Jupiter

Voyager 1 Image of Jupiter's Great Red Spot in False Color.jpg
Voyager 1 Jupiter Io Europa.jpg

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. 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. The Romans named the planet after the Roman god Jupiter. 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.)

Jupiter voy1.jpg

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). 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. Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 63 moons, including the four large moons called the Galilean 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. 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. 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.

Selected article

Cloud pattern on Jupiter in 2005
The atmosphere of Jupiter is the largest planetary atmosphere in the Solar System. It 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 water. Although water is thought to reside deep in the atmosphere, its directly measured concentration is very low. The oxygen, 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 fluid 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.

Selected biography

Eugene Shoemaker at a stereoscopic microscope used for asteroid discovery
Eugene Merle Shoemaker (or Gene Shoemaker) (April 28, 1928 – July 18, 1997), American geologist, was one of the founders of the fields of planetary science.

Born in Los Angeles, California, he is best known for co-discovering the Comet Shoemaker-Levy 9 with his wife Carolyn Shoemaker and David Levy. For his Ph.D. degree at Princeton (1960), Shoemaker studied the impact dynamics of Barringer Meteor Crater, located near Winslow, Arizona. To understand the dynamics, Shoemaker inspected craters that remained after underground atomic bomb tests at the Nevada Test Site at Yucca Flats. He found a ring of ejected material that included shocked quartz (coesite), a form of quartz that has a microscopically unique structure caused by intense pressure.

Shoemaker helped pioneer the field of astrogeology by founding the Astrogeology Research Program of the U.S. Geological Survey in 1961 at Flagstaff, Arizona and he was its first director. He was prominently involved in the Lunar Ranger missions to the Moon, which showed that the Moon was covered with a wide size range of impact craters. Shoemaker was also involved in the training of the American astronauts. He himself was a possible candidate for an Apollo moon flight and was set to be the first geologist to walk on the Moon but was disqualified due to being diagnosed with Addison's disease, a disorder of the adrenal gland. Shoemaker would train astronauts during field trips to Meteor Crater and Sunset Crater near Flagstaff.

He was awarded the Wetherill Medal from The Franklin Institute in 1965.


Jupiter Atmosphere ˑ Exploration (Voyager 2) ˑ Rings

Major Moons ˑ Io ˑ Europa ˑ Ganymede ˑ Callisto

Astronomers: Galileo Galilei ˑ Gan De ˑ Gerard Kuiper ˑ Giovanni Domenico Cassini

See Also: Formation and evolution of the Solar System ˑ Gas Giant ˑ Nebular hypothesis

Bold articles are featured.
Italicized articles are on dwarf planets or minor moons.



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