# NASA - National Aeronautics and Space Administration

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Pinwheel Activity Demos Jupiter's Great Red Spot

Montage showing Jupiter and its Great Red Spot and, from top to bottom, the moons Europa, Ganymede and Callisto. Image credit: NASA/JPL

Each of the three frames in this animation is a mosaic of six images that were map-projected to a uniform grid of latitude and longitude. There is a nine-hour separation between the first two frames and seventy minutes between the next two. All of the images were taken on June 26, 1996. Image credit: NASA/JPL
When 17th century astronomers first turned their telescopes to Jupiter, they saw a conspicuous reddish spot on the giant planet. Dubbed the Great Red Spot, it is a gigantic, cyclonic storm still churning today on Jupiter. It looks similar to Earth's hurricanes but is much larger - in fact, two Earths could fit inside!

This enormous storm was one of many features studied by the Galileo spacecraft, which launched 20 years ago, on Oct. 18, 1989. The mission studied Jupiter, its magnetosphere and many of its moons. The long-lasting mission ended on Sept. 21, 2003.

To celebrate the Galileo mission's 20th anniversary, we've pulled a favorite fun activity from the archives: The Great Red Spot Pinwheel.

Summary: Students create a model of Jupiter's Great Red Spot rotating like a pinwheel around a central point to demonstrate the atmospheric dynamics of the cyclonic storm.

Background: This activity can be used in a math context (measuring speed), or a science context (atmospheric dynamics -- understanding that there's lots of interaction going on within the Great Red Spot system). Or, it can simply be used to illustrate that we can understand what we see and represent in an understandable way.

Activity description: Show the Great Red Spot rotation movie, which you can see here on this page. Where is the storm rotating the fastest? The slowest? Does it all rotate in the same direction?

It takes six days for the Great Red Spot to make one rotation. Assuming that each part of the storm takes the same amount of time to rotate (which isn't quite true), the outer part of the storm must travel faster because it must travel farther in those six days.

Have some students (six to eight) stand in a line and have them rotate like a pinwheel (representing a "slice" or "spoke" of the storm). To keep them in a straight line, have them hold hands or onto a rope or a long stick -- or have them slowly take one step at a time and make sure they are in a line after each step. Either way, students will quickly realize that those on the outside must take bigger steps (hence traveling a greater distance for each unit of time, which in the second case is one "step" command).

Who is moving the fastest? The slowest? Add another line of students like a spoke and have them continue rotating. What happens? What if there are three or four lines of students rotating? What if you represent the whole storm (like a crowded skating rink)?

Students will start bumping into each other, especially on the outside where they must move faster. This is representative of what happens in cyclonic storms like the Great Red Spot. For further discussion, make the storm move faster or slower and notice the frequency with which students bump into each other.