|Jupiter’s system is very complex, yet many of its processes resemble processes that exist on Earth, magnified by the enormity and extremity of Jupiter. In studying Jupiter, we can learn more about atmospheric effects and interactions that are subtle on Earth, such as interactions between the magnetosphere and the atmosphere. Studies of Jupiter will help us understand the chemistry and behavior of Earth’s own comparatively thin, but very precious, atmosphere.
Jupiter has an immense, complex atmosphere, which bristles with lightning and swirls with huge storm systems. One of these, the Great Red Spot, is a giant storm that has existed for at least 100 years, and perhaps longer, as the great astronomer Galileo Galilei reported seeing a similar structure over 380 years ago! Some scientists theorize that beneath the atmosphere there is no solid mass at the center of Jupiter, but that the planet’s unique temperature and pressure conditions sustain a core whose density is more like liquid or slush.
Jupiter’s interior pressure may reach 100 million times the surface pressure on Earth. Its magnetic field is immense, even in proportion to the size of the planet, stretching millions of miles into the solar system. Trapped within Jupiter’s magnetosphere are enough charged particles to make the inner portions of Jupiter’s magnetosphere the most deadly radiation environment of any of the planets, both for humans and for electronic equipment. And the “tail” of Jupiter’s magnetic field – that portion stretched behind the planet as the solar wind rushes past – has been detected as far as Saturn’s orbit. Electrical activity in Jupiter is so strong that it pours billions of watts into Earth’s own magnetic field every day.
With its numerous moons and several rings Jupiter is sometimes called a “mini-solar system.” The moons are amazingly different from each other: some are icy, some rocky, some cratered, and some remarkably smooth. The four largest – Io, Europa, Ganymede, and Callisto – were discovered by Galileo Galilei in 1610, and are collectively called the Galilean satellites. Ganymede is the largest planetary moon in the solar system; eight outer moons are likely captured asteroids. Io, the fourth largest moon, is about the same size as Earth’s Moon, but is the most volcanic body in the solar system. When the Voyager 1 spacecraft passed through Jupiter’s realm in 1979, it spotted nine active volcanoes on Io, spewing sulfurous gases and solids as high as 300 kilometers (185 miles) above the surface at velocities up to 1 km/sec! Over 300 active and inactive volcanic vents have been identified on Io. The moon Europa has attracted increased interest as evidence mounts that a liquid ocean may lie beneath the frozen crust. Might there be life there? In recent years, life has been discovered on Earth in extreme environments where no one had thought life could possibly exist–too dark, too cold, too hot, too salty, and so forth. These discoveries lead to speculation that life of some sort might exist in other places in our solar system – perhaps in Europa’s frigid, subsurface ocean.
In the late 1970s, NASA’s two Voyager spacecraft discovered Jupiter’s rings: a flattened main ring and an inner, cloud-like ring, called the halo, both composed of small, dark particles. One Voyager image seemed to indicate a third, faint outer ring. New data from NASA‘s Galileo spacecraft, currently in orbit about Jupiter, reveal that this third ring, known as the gossamer ring because of its transparency, consists of two rings. One is embedded within the other, and both are composed of microscopic debris from two small moons, Amalthea and Thebe. Scientists believe Jupiter’s ring system is formed by dust kicked up as interplanetary meteoroids smash into the giant planet’s four small inner moons. It is likely that the main ring comes from the tiny moons Adrastea and Metis.