Jupiter and Saturn Jupiter and Saturn are the two largest and best known Jovian planets. Others include Uranus and Neptune. Pluto is considered as a separate object. Great Red Spot a) Earth Based View b)View from Hubble The four brightest moons are called the Galilean satellites after Galileo

While Jupiter is known for its four brightest moons and the red spot, Saturn is known for its extensive ring system. a) Earth Based View b)View from Hubble

Discovery of Uranus Uranus was discovered by William Herschel while cataloging stars. Uranus slowly moved among the stars proving it was a planet. Herschel wanted to name the planet “George” but was talked into Uranus by Johann Bode. a) Earth view b) Voyager 2 view

Discovery of Neptune a) Earth view The orbit of Uranus was being gravitationally perturbed by another unknown planet. After two years of searching, they found the planet within 2 degrees of its predicted position. a) Voyager 2 view

Physical Properties Notice for example that Jupiter is 315 times more massive than the Earth and 11 times bigger while being less dense.

It is difficult to measure the rotation rates of the Jovian planets because they have no “surface” to watch as they rotate. With nothing to tie them down different parts of the atmosphere rotate at different speeds (differential rotation). The Jovian planets are also known as the gas giants.

Jupiter’s Atmosphere Because of its high escape velocity, Jupiter has been able to retain all the lighter gasses including hydrogen and has the same chemical proportions as when it was created 4.6 billion years ago. It consists of 86% hydrogen, 14% helium, traces of methane, ammonia, and water vapor. After its four bright moons, Jupiter is best known for its cloud bans. The bands are the result of convection currents in the atmosphere. Lighter warmer gasses tend to ride on top (ammonia) and the cooler heavier gasses sink down (ammonium hydrosulfide) giving a light/dark pattern on the surface.

Weather on Jupiter In addition to the large scale band structures on Jupiter there are smaller structures. The most famous being the great red spot which is a hurricane storm which has been raging for over 300 years. Spacecraft have detected lightening and aurora. Show Fix laser disk video: side 2, at 15559

Saturn’s Atmosphere Saturn is not as colorful or turbulent as Jupiter. This may be due to the fact that Saturn is cooler because it is further away from the Sun. It does not contain as large of storms not are they permanete. It also has enough gravity to hold on to all the gasses and consists of 92.4% hydrogen, 7.4 helium, and traces of methane and ammonium The most famous thing about Saturn is its rings.

“Real” color Color enhanced to show structure.

Some storms on Saturn actually encircle the planet. Sequence of images from Hubble