How did Jupiter get its red spot?
It was made by a storm hundred of years ago.
The so called 'Red Spot' which is visible in Jupiter's atmosphere is a gigantic storm which has been in existence for several hundred years.
The great red spot is actually a giant hurricane that has been on Jupiter for thousands of years. The gases on Jupiter make the storm appear red. Jupiter fits in the column of a gas giant, so that explains the gas part. So really the great red spot is just a "landmark" on Jupiter, and no other planet that we know of has one.