The Outer Planets: Jupiter, Saturn, Uranus, and Neptune
hapter CHARACTERISTICS OF JUPITER NNhe fifth planet from the Sun and the solar system s largest planet by far is Jupiter More than 1 300 Earths would fit inside it The planet is one of the bright est objects in the night sky and even a small telescope can reveal its multicolored stripes These stripes are bands of clouds being pushed around the planet by strong east west winds Jupiter is a world of complex weather patterns Its most prominent feature is an orange red oval called the Great Red Spot The oval is a storm system that has lasted at least 300 years and is bigger across than Earth and Mars combined Bands of pastel colored clouds encircle the giant planet Jupiter which appears in a composite of images taken by the Cassini space craft The small black disk at lower left is a shadow cast by Jupiter's moon Europa The enormous storm called the Great Red Spot is visible at lower right The raw images were taken in two colors which were processed to simulate Jupiter's natural colors NASA JPL University of Arizona
CHARACTERISTICS OF UPITER Jupiter is not just bigger than Earth it is also fundamentally different in composition Jupiter has no solid surface It is formed of the same elements in roughly the same propor tions as the Sun and other stars Like Saturn it is made almost entirely of hydrogen and helium in liquid and gaseous forms Although A map shows the entire visible surface of Jupiter including its bands of clouds the Great Red Spot and many smaller oval storms in the planet's massive atmosphere The map is a cylindrical projection like maps of Earth that show the planet stretched flat onto a rectangle It was generated by computer from 36 images taken by the Cassini space craft and processed to simulate the planet's true colors Jupiter's polar regions appear less clear because of the angle of the spacecraft Scam era and because they were covered by a thicker base NASA JPL Space Science Institute II
THE OUTER PLANETS JUPITER SATURN URANTS AND NEPTUNE Jupiter is huge it would have to be about 80 times more massive to generate nuclear reactions and become a star Hot glowing lava erupts from a volcano on Jupiter's moon lo in an image captured by the Galileo orbiter It is a mosaic of several images including enhanced color images taken in visible light The bright white yellow and orange at left are false colors added to images taken at infrared wave lengths to indicate temperature White is the hottest and orange the coolest NASA JPL California Institute of Technology Nevertheless Jupiter reigns at the center of a system of dozens of moons like a minia ture solar system Four of the moons are quite large and would probably be considered plan ets themselves if they did not orbit a planet They are remarkably dissimilar worlds Io is the most volcanically active body in the solar system Frequent eruptions renew its surface and cover over any craters that form Europa s surface is also fairly young but its features are smoothed not by fiery lava but by water ice 12
CHARACTERISTICS OF UPITER which possibly flows up from beneath the sur face and freezes Europa may harbor an ocean of warm salty water just under its icy crust Callisto has an ancient crater scarred surface that seems to have been largely undisturbed by geologic activity for some 4 billion years Ganymede the solar system s largest moon is bigger than the planet Mercury and has a plan etlike magnetic field An outer planet Jupiter is much farther from the Sun than Earth and the other inner planets are Its orbit lies between the main asteroid belt and Saturn's orbit Its inner planetary neighbor Mars orbits between the Jupiter's Galilean moons from left to right Io Europa Ganymede and Callisto appear in a montage created with images from the Galileo orbiter The images are scaled to show the moons sizes relative to one another NASA JPL Caltech 13
