As mentioned earlier, one of Saturn’s jet streams is a narrow meandering river of air with alternating crests and troughs (see Figure 10.8). This feature, located near latitude 45° north, is similar to Earth’s jet streams, where high-speed winds blow generally from west to east but with alternate wanderings toward and away from the pole. Nested within the crests and troughs of Saturn’s jet stream are anticyclonic and cyclonic vortices. They appear remarkably similar in both form and size to terrestrial high- and low-pressure systems, which bring alternating periods of fair and stormy weather as they are carried along by Earth’s jet streams. This similarity in jet streams on Saturn and Earth is a good illustration of one reason why astronomers study other planets: to compare them to each other and to Earth. From observing and analyzing similar atmospheric systems on other planets, they often learn more about the way Earth’s weather works.