The History Of Jupiter

With a mass more than 300 times the mass of Earth, the planet Jupiter is the largest planet discovered in the Solar System. It is named after the Roman king of the gods. To the Greeks, he was also known as Zeus.

Jupiter is located fifth from the Sun, and was known as the “bright wandering star” in ancient times. It is in fourth position as one of the brightest objects after the Sun, Moon, and Venus. Galileo is credited with discovering four of its moons in 1610. Scientists believe Jupiter is 4.6 billion years old.

The Orbit Of Jupiter

The orbit of Jupiter is oval in shape. The perihelion, or point at which the planet is closest to the sun, is 460 million miles (741 million km), whereas its aphelion, or the point at which the planet is farthest from the sun, is 507 million miles (816 million km).

The orbit of Jupiter is completed in 4,330 Earth days. It rotates at the fastest speed of all the planets, with a day being completed in 9 hours and 56 minutes. As a result of this fast rotation, the planet bulges at the Equator and is flat at the poles due to the speed.

Expeditions To Jupiter

There have been a few expeditions to Jupiter. The first expedition by the United States was launched in 1972. This spacecraft, Pioneer 10, arrived in Jupiter’s atmosphere in December 1973. Even though it was 81,000 miles from the surface of Jupiter, the spacecraft was able to illustrate how strong was the radiation belt of Jupiter, while also providing information on the level of hydrogen and helium contained within its atmosphere.

In 1974, Jupiter was visited by the Pioneer-Saturn spacecraft, which took photographs of the North and South poles on Jupiter. This expedition was also responsible for providing information on the “Great Red Spot” and Jupiter’s magnetic field. The temperature on Jupiter was also determined during this expedition.

The following two expeditions to Jupiter were in 1979 by Voyager 1 and Voyager 2. These spacecrafts were used to take photographs of the four Galilean moons, and view lightning in Jupiter’s atmosphere.

After this expedition, the European Space Agency launched a spacecraft to visit Jupiter. The Ulysses visited the atmosphere of Jupiter in 1992, and collected further data on the North and South poles.

The United States’ spacecraft Galileo went into orbit around Jupiter in 1995. This spacecraft contained a probe, which was released into the atmosphere of Jupiter. The probe was used to measure the water and chemical content within Jupiter’s atmosphere. Galileo was also responsible for detecting the possibility of an ocean on Jupiter’s Europa satellite.

The Cassini spacecraft visited Jupiter in 2000. Its main purpose was to visit planet Saturn, however it flew by Jupiter and took thousands of pictures for a period of seventy days. This expedition was able to observe and record the debris from the impact of the Comet Shoemaker-Levy 9 into Jupiter’s atmosphere in 1994. Cassini was also able to document the large number of long-lasting storms occurring on Jupiter, while revealing more information about the wind patterns on Jupiter.

Exploring A Day On Jupiter

As compared to a day on Earth, a day on Jupiter is extremely short – less than ten hours! As one of the gas planets, on entering the atmosphere of Jupiter the first thing someone would notice, is the high concentration of gases. Hydrogen is present in a concentration of 86 percent, while the concentration of helium is 14 percent.

There are also small amounts of water, methane, ammonia, and carbon monoxide present in Jupiter’s atmosphere. When viewed from space, these gases are concentrated into particular areas. For example, frozen ammonia is located higher in the atmosphere, forming a white cloud-like layer. With the levels of hydrogen and helium present, Jupiter could have become a star if it was much bigger.  Many scientists jokingly refer to Jupiter and its many satellites as a “mini solar system.”

Higher in its atmosphere, hydrogen is converted into a liquid, whereas further down, hydrogen is converted into a metal, which contributes to Jupiter’s strong magnetic field (20,000 X greater than Earth’s). The magnetic field contains a radiation belt of electrons and ions along with Jupiter’s rings and satellites.

Compared to the gas layers surrounding it, it is believed the core of Jupiter is a thick liquid, but hardly anything is known about it.

Another thing apparent while exploring Jupiter is its temperature. The temperature of Jupiter can be –234 degrees Fahrenheit in the highest layer of the atmosphere.  

The most well known feature on Jupiter is the Great Red Spot (GRS). This is an area of twirling winds of gas similar to the Earth’s hurricane storms. The Great Red Spot has a diameter at least 2-3 times the size of Earth, and it thought to contain sulfur and phosphorus. Due to the numerous storms on Jupiter, the wind patterns are quite active, and contribute to the “banded” appearance of Jupiter, especially when viewed from outer space.

Like Saturn, Jupiter also has rings that surround it, divided into three sections. The rings of Jupiter consist largely of particles of dust and debris, and as a result Jupiter’s three rings are faint and dark in appearance.  The Main ring (4,000 miles wide) is located in the middle and flattened in shape, whereas the Halo inner ring (18,952 miles wide) resembles a cloud-like layer. The third almost transparent Gossamer ring system is made up of two rings, with the inner ring being 32,348 miles wide, and the outer ring being 24,854 miles wide.

Based on the gaseous structure and hydrogen composition of the planet, no life forms have been found on Jupiter.  

The Satellites Of Jupiter

There are 63 satellites associated with Jupiter, the most satellites of any planet. The four main ones are the Galilean moons. The satellites of Jupiter can be divided into two different categories – the regular satellites and the irregular satellites.

The Regular Satellites

The regular satellites consist of the four Galilean moons – Io, Europa, Ganymede, and Callisto – along with four smaller satellites.

Io

The first Galilean moon Io contains a large number of volcanoes. This moon is also home to volcanic geysers and wide lakes of lava, and is said to be one of the most interesting places in the Solar System. It is constantly releasing its ashes, volcanic gases, and other debris into outer space. This results in a band of atoms and ions surrounding the planet due to the gases released.

With mountains reaching 16 km in height, their height is higher than what is commonly found on Earth.

Io was discovered on January 7, 1610. It has a radius of 1,815 km and is located 421,000 km from Jupiter. It orbits Jupiter every 1.77 Earth days.

Europa

The second moon of Jupiter is Europa. It is covered in ice, giving its surface a smooth appearance, and is highly reflective of sunlight.

With a 2-mile long thick layer of ice, Europa orbits Jupiter ever 3.55 Earth days.

Scientists believe an ocean of either liquid water or slush exists underneath the layers of ice on Europa that might be warm enough to support life. It has a radius of 1,565 km.

Ganymede

The third moon Ganymede is the largest of all the satellites in the Solar System. With a radius of 3,280 miles, Ganymede is larger than Mercury. This moon has a variety of different landscapes such as mountainous regions with valleys below, areas of lava eruptions, and craters.

Ganymede is located a distance of 1.07 million km from Jupiter. The core of Ganymede is thought to contain solid rock, with areas of water ice on the surface.

When viewed from space, Ganymede’s surface has a variety of light and dark blotches showing its ridges and craters respectively. It orbits Jupiter ever 7.15 Earth days, and has its own magnetic field.

Callisto

As the fourth moon of Jupiter, Callisto has a radius of 2,400 km and is slightly smaller than Ganymede. It is located a distance of 1.883 million km from Jupiter. The highest number of craters and impact basins are found on its typography.

The two largest impact basins are Valhalla and Asgard. Valhalla has a diameter of 600 km, while Asgard has a 1,600 km diameter.

Callisto lacks an atmosphere, but possess a solid upper crust. It is believed that below the crust is a salt ocean that extends for 10 km. Callisto orbits Jupiter every 16.7 Earth days.

Other Regular Satellites

The four smaller remaining regular satellites are Amalthea (V), Thebe (XIV), Adrastea (XV), and Metis (XVI). There is a lot still to be discovered about these four satellites. What is known is that Metis and Adrastea provide the debris for the Gossamer ring.

Also the surface of Amalthea, Jupiter’s fifth moon, contains a variety of craters similar to Earth’s moon. The largest crater on Almathea is called Pan and measures a width of 100 km, and a depth of 8 km.

The landscape of Amalthea is composed of various colors of brown, red, and green. The brown and red patches are due to sulfur being present, however the reason for the green patches is unknown.

The Irregular Satellites

The irregular satellites of Jupiter do not all have a circular orbit, compared to the regular satellites. The largest irregular satellite is Himalia, with a diameter of 150 million km. It was first discovered in 1904, whereas the last irregular satellite was discovered in 2003. Unlike the regular satellites, it is believed the irregular satellites where trapped within Jupiter’s powerful magnetic field. The full list of Jupiter’s satellites and their year of discovery appear below:

Table 1: The Satellites Of Jupiter. (Space Today 2004)

Statistics About Jupiter

Discovered By	Known by the Ancients
Date of Discovery	Unknown
Average Distance from the Sun	Metric: 778,412,020 km English: 483,682,810 miles Scientific Notation: 7.7841202 x 108 km (5.20336 A.U.) By Comparison: 5.203 x Earth
Perihelion (closest)	Metric: 740,742,600 km English: 460,276,100 miles Scientific Notation: 7.407426 x 108 km (4.952 A.U.) By Comparison: 5.036 x Earth
Aphelion (farthest)	Metric: 816,081,400 km English: 507,089,500 miles Scientific Notation: 8.160814 x 108 km (5.455 A.U.) By Comparison: 5.366 x Earth
Equatorial Radius	Metric: 71,492 km English: 44,423 miles Scientific Notation: 7.1492 x 104 km By Comparison: 11.209 x Earth
Equatorial Circumference	Metric: 449,197 km English: 279,118 miles Scientific Notation: 4.49197 x 105 km
Volume	Metric: 1,425,500,000,000,000 km3 English: 342,000,000,000,000 mi3 Scientific Notation: 1.4255 x 1015 km3 By Comparison: 1316 x Earth
Mass	Metric: 1,898,700,000,000,000,000,000,000,000 kg Scientific Notation: 1.8987 x 1027 kg By Comparison: 317.82 x Earth
Density	Metric: 1.33 g/cm3 By Comparison: 0.241 x Earth
Surface Area	Metric: 62,179,600,000 km2 English: 24,007,700,000 square miles Scientific Notation: 6.21796 x 1010 km2 By Comparison: 121.9 x Earth
Equatorial Surface Gravity	Metric: 20.87 m/s2 English: 68.48 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 214 pounds on Jupiter.
Escape Velocity	Metric: 214,300 km/h English: 133,200 mph Scientific Notation: 59,540 m/s By Comparison: 5.33 x Earth
Sidereal Rotation Period (Length of Day)	0.41354 Earth days 9.925 hours By Comparison: 0.4147 x Earth
Sidereal Orbit Period (Length of Year)	11.8565 Earth years 4330.6 Earth days
Mean Orbit Velocity	Metric: 47,051 km/h English: 29,236 mph Scientific Notation: 13,069.7 m/s By Comparison: 0.0439 x Earth
Orbital Eccentricity	.04839 By Comparison: 2.90 x Earth
Orbital Inclination to Ecliptic	1.305 degrees
Equatorial Inclination to Orbit	3.12 degrees By Comparison: 0.0178 x Earth
Orbital Circumference	Metric: 4,774,000,000 km English: 2,996,000,000 miles Scientific Notation: 4.774 x 109 km By Comparison: 5.165 x Earth
Effective Temperature	Metric: -148 °C English: -234 °F Scientific Notation: 125 K
Atmospheric Constituents	Hydrogen, Helium Scientific Notation: H2, He
Table 2: Concise statistics on the planet Jupiter (N.A.S.A. 2006)

References

Encyclopedia Britannica. “Jupiter.” 2006. Encyclopedia Britannica Premium Service. 2006 http://www.britannica.com/eb/article-9110150

Gierasch, Peter J., and Philip D. Nicholson. "Jupiter." World Book Online Reference Center. 2004. World Book, Inc http://www.worldbookonline.com/wb/Article?id=ar293080

National Aeronautics and Space Administration (N.A.S.A). “Jupiter: Facts & Figures.” 2006 http://solarsystem.nasa.gov/planets/profile.cfm?
Object=Jupiter&Display=Facts

Space Today Online. “Exploring The Jupiter System.” 2004 http://www.spacetoday.org/SolSys/Jupiter/JupiterMoons.html

Jupiter Images