Jupiter is nothing like our own familiar Earth. It is not a rocky body at all, with a good solid surface that you can walk on, but is what is called a gas giant. There is no visible solid surface at all, and in effect Jupiter is all atmosphere.[caption id="attachment_14" align="alignright" width="300"] Jupiter’s atmosphere[/caption]
Jupiter is by far the largest planet in the Solar System, with over 300 times the mass of the Earth. Its enormous gravitational pull can drag smaller bodies out of their orbits and it has an effect on many other bodies. Fortunately, Earth is too far away to be directly affected.
Given Jupiter’s enormous size and influence it seems surprising that it is mostly composed of the two lightest elements – hydrogen and helium. But it is so large – around a tenth of the diameter of the Sun itself – that it dominates the planets.
If you were to fall towards Jupiter in a spacecraft, you would see your surroundings becoming more and more cloudy and murky. The temperature and gas pressure outside would rise and rise – and eventually you would be crushed and roasted, no matter how well-made your spacecraft.
What we see through telescopes are the top layers of an incredibly dynamic atmosphere thousands of miles deep. Convection caused by internal heat and Jupiter’s rapid spin of one revolution in under 10 hours generate violent weather systems on a colossal scale. Turbulent winds shriek along at hundreds of miles an hour between vast cyclonic systems and thunderstorms. Even the uppermost layers would mean a white-knuckle ride for any astronaut foolhardy enough to enter. Moreover, the lack of any solid surface means that there are no topographical features to mitigate atmospheric disturbances. Some Jovian storms may last for decades or even centuries.
The atmosphere is drawn into horizontal bands known as belts and zones. Zones are usually a light creamy colour while belts appear beige or orangey-brown. The most prominent storm system is the Great Red Spot, located in the south temperate belt. The GRS, as it’s referred to by astronomers, is an enormous anti-cyclonic storm at least twice the size of Earth that has been raging since it was first observed in the 17th century. Its colour varies from dark red through to pale orangey-yellow and it is the favourite subject for observation in the Jovian atmosphere. There is a similar but smaller storm called Oval BA located not far from the GRS. Oval BA is much younger than the GRS and formed in 2000 from the merger of three other storms.
Please see our other pages about Jupiter listed in the submenu to the About Jupiter link.
In addition, there is also a very valuable repository of information about Jupiter at this NASA page: http://nssdc.gsfc.nasa.gov/planetary/planets/jupiterpage.html