Jupiter is the fifth planet from the sun, and is a gas giant. The sun is one thousand times heavier than Jupiter, but Jupiter is two and a half times heavier than all of the other planets in our solar system put together!
Jupiter is made up of hydrogen and helium, and has no defined outer surface. It may have a rocky inner core made up of metallic elements, but astronomers don’t know more about Jupiter’s core than this basic outline.
The Great Red Spot is a large storm that has been going for hundreds of years (and possibly much longer). It was first observed by Giovanni Cassini, an Italian astronomer, during the 1600s. When Cassini first observed the Great Red Spot, it was a long, oval shape.
This storm is so large, that it is up to two or three times bigger than Earth! The Great Red Spot is over 40,000 km in diameter, and could be seen easily with a telescope from your backyard. Even though the Great Red Spot is large now, it is slowly shrinking in size. The size of the Great Red Spot is half as wide as it was 100 years ago, and astronomers believe that it will be a round, circular shape by 2040.
Figure 1: Jupiter’s Great Red Spot. Image credit: NASA (public domain).
Jupiter’s atmosphere is made up of hot gases that are constantly moving. These gases are rising and falling, and swirling throughout the atmosphere. Like on Earth, as cooler gas moves down through the atmosphere, the swirling intensifies, but there is no solid ground on Jupiter to slow it down. When the swirling gases merge into one another, they create giant circling storms. Astronomers believe that several giant storms came together and formed the Giant Red Spot. The Great Red Spot keeps going by drawing hot gases from above, and cooler gases from below. This keeps the storm in motion. Winds inside the storm are moving at a speed of 270 miles per hour (434 km per hour).
The red colour of the Great Red Spot is thought to be caused by organic molecules, red phosphorous, or other elements that come from inside Jupiter. Some theories propose that the colour is caused by reactions between these chemicals in Jupiter’s atmosphere, or by lightning striking the molecules. The colour is not always the same, either: sometimes it is dark red, while at other times it is a pale pink colour, or even white! Perhaps Jupiter’s Great Red Spot is not so red after all!