Planets
Uranus
(Contd. from page 2...)Uranus' atmosphere is about 83% hydrogen, 15% helium and 2% methane. Like the other gas planets, Uranus has bands of clouds that blow around rapidly. But they are extremely faint, visible only with radical image enhancement of the Voyager 2 pictures (right). Recent observations with HST (left) show larger and more pronounced streaks. Further HST observations show even more activity. Uranus is no longer the bland boring planet that Voyager saw! It now seems clear that the differences are due to seasonal effects since the Sun is now at a lower Uranian latitude which may cause more pronounced day/night weather effects. By 2007 the Sun will be directly over Uranus's equator. Uranus' blue color is the result of absorption of red light by methane in the upper atmosphere. There may be colored bands like Jupiter's but they are hidden from view by the overlaying methane layer. Like the other gas planets, Uranus has rings. Like Jupiter's, they are very dark but like Saturn's they are composed of fairly large particles ranging up to 10 meters in diameter in addition to fine dust. There are 11 known rings, all very faint; the brightest is known as the Epsilon ring. The Uranian rings were the first after Saturn's to be discovered. This was of considerable importance since we now know that rings are a common feature of planets, not a peculiarity of Saturn alone. Voyager 2 discovered 10 small moons in addition to the 5 large ones already known. It is likely that there are several more tiny satellites within the rings.