Jupiter gets naked

23.05.2010

Many young children and pupils around the world are taught that the best known features of our solar system include Saturn’s numerous rings, Jupiter’s great stripes, Mars’ stark redness and Earth’s vast quantities of water. All are constant, unchanging signs that our solar system is functioning normally. It may well therefore come as a shock for those in the know that one of these qualities has been altered indefinitely. Jupiter is losing its stripes and one of its widest belts has already vanished.

To fully understand the impact of this recent development, it is essential to know the identity of this stripe. This particular band of brown clouds is twice as wide as earth and twenty times as long and as such, this vast stripe could have been seen from earth with the naked eye. The origins and age of this group of clouds were relatively unknown, having believed to have existed since the planet originally formed. Located just below Jupiter’s Equator in a mirror image position to a similar band of clouds just above Jupiter’s Equator earned it the name ‘South Equatorial Band’. Both the North and South Equatorial Bands were so large that few clouds gathered between or near them, instead being ‘sucked in’ by the high winds and pressures of these clusters of clouds. Now only the North Equatorial Band seems to remain, itself potentially to disappear in the somewhat near astronomical future as well.

News that this band of clouds had disappeared shocked astronomers throughout the world, particularly as there were few signs that it was vanishing until this month. Nobody is entirely sure about the reasons behind its loss though Jupiter experts believe that it has only disappeared for a short time. Instead, they suppose that one of the largest ammonia storms is brewing on Jupiter, a storm so large that the likes of which have never been seen before in scientific memory. In the right weather conditions on Earth, thin, white wispy clouds, (cirrus clouds), form at very high altitudes. On Jupiter, the same phenomenon occurs, though this time the clouds are comprised of ammonia particles rather than water. They suspect that changes in global wind patterns have transported vast quantities of ammonia into the clear, cold zones of clouds directly above the South Equatorial Belt and that these have gathered together to form pale-coloured clouds that have blocked out the brown clouds.

However, as it is difficult to voyage into Jupiter’s corrosive atmosphere with our present technology, this remains to be proved, especially as astronomers are still uncertain regarding the chemical composition of Jupiter’s brown belts or why ammonia affects the Southern Equatorial Belt more strongly than the Northern Equatorial Belt. The reappearance of the belt is believed to occur rapidly and spontaneously. A slight change in pressure at one point in the belt will herald the arrival of storms so large and impressive that they could be seen from almost any point in the solar system.

The length of time that these ammonia clouds brew for will determine whether the northern belt will start to disappear or whether the southern belt will rapidly re-appear first. Either way, the answer to this question will be seen in dynamic changes in Jupiter’s atmosphere over the next few years, so keep an eye out in the night sky for a spectacular show.