In late 2010, NASA’s space probe Cassini started observing a huge storm on Saturn lasting for several months. In recent days, an article was published on the journal “Nature Geoscience” that provides an explanation for this phenomenon that had been observed a number of times in the last 140 years but had remained mysterious. According to a team led by Cheng Li of CalTech, Pasadena, the presence of water is the key to its origin.
This type of storm occurs once every 30 Earth years, which means once every Saturn year. For this reason, since the instruments to observe this planet have been powerful enough to see it, astronomers have wondered about its causes. The presence of the space probe Cassini allowed to collect the data needed to explain it.
The basic idea for the explanation is that water vapor is heavier than the hydrogen and helium which form the bulk of Saturn atmosphere. The consequence is that once each giant storm releases its huge amount of rain in the clouds the air becomes lighter than atmosphere below. This temporarily blocks the convection, where warm, moist air rises and cold, dense air sinks, that create new clouds and storms.
After one of these giant storms, for decades the warm air in the depths of Saturn atmosphere is too wet and dense to rise. The air in the upper layer must cool down, dispersing its heat into space. Only then its density becomes higher than the warm, wet air below.
In Cheng Li’s opinion, the episodic nature of these storms indicates that in the depths of Saturn atmosphere there’s more water than in Jupiter’s in relation to the other constituents. According to this theory, that’s why there are storms of such great magnitude on Saturn while on Jupiter storms are relatively small and frequent.
The presence of water is confirmed by observations made with various telescopes. Several scientists are studying the presence of oxygen, one of the elements that form water, and other volatile substances that change state at relatively low temperatures on Saturn and Jupiter. That’s because they provide important clues about those planets’ formation, which is believed to have taken place before the other planets.
In essence, the massive storms on Saturn are a spectacular phenomenon but also interesting from a scientific point of view. Their study provides more information on the conditions existing in the early stage of the formation of the solar system, which means also those that led to the formation of the Earth.
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