We suffer our share of devastating hurricanes and typhoons seasonally.
But imagine a belt of super-storms that ravages a planet for an entire year.
That’s happening 1 billion miles away on the colossal gas giant Saturn. The storm system erupted almost exactly one year ago. Starting as a small atmospheric spot, within a month it completely wrapped around Saturn’s northern hemisphere like a Boa constrictor, blanketing one-fifth of the northern hemisphere.
For the past year the Saturn-circling NASA Cassini spacecraft has chronicled the storm’s chaos. Cassini’s cameras have kept a close-up eye on a sinuous, churning, and roiling atmosphere.
For the first half of 2011, Cassini’s radio and plasma wave instruments detected super-lighting erupting in what must be towering thunderheads at the planet’s cloud tops. The Zeus-class thunderbolts died away by mid-2011, but the turbulent clouds still linger in the atmosphere with swirling waves, vortices, and eddies.
Saturn is so far from the sun that you could barely warm your hands in sunlight streaming through a spacecraft’s window. The sun is a feeble 1/100th as bright as seen from Earth. Therefore, whatever’s driving the storm should be coming from deep within Saturn. The ringed planet radiates three times as much energy as it receives from the sun due to gravitational contraction.
However, observations have shown that Saturn’s monster storms happen in 20-to-30 year cycles. Years before Cassini was launched, the Hubble Space Telescope snapped a similar outburst in 1993, (pictured below) but it died out after 55 days. Other white storms were sighted in 1960, 1933, 1903, and 1876. The 1903 storm lasted 155 days and was the record-holder until now.
This would seem to correspond to Saturn’s seasonal variations, because the planet is tilted like Earth and completes one orbit every 30 years. Saturn had its spring equinox in mid-2009. Since then, sunlight has been falling more directly onto the northern hemisphere. It won’t be summer solstice in the northern hemisphere until 2017.
Perhaps the stronger seasonal sunlight causes the convection of rising and sinking columns of gas within the atmosphere to become more energetic. This enhanced upwelling might trigger colossal super-storms.
2012 soothsayers quickly latched onto the Saturn’s atmospheric “volcanoes” (as planetary scientist Andrew Ingersoll describes them). According to one “end of times” website a mythical rogue planet named Hercolumbus is using its extraordinary magnetic field to stir up Saturn (never mind that Saturn is embedded in a huge magnetosphere of its own).
Cassini is dramatically showing that orbiting a gas giant planet is invaluable to tracking its dynamic atmosphere and petulant super-storms. Beyond Saturn, there are bizarre phenomena taking place in the atmospheres of Uranus and Neptune as well.
The Voyager flybys of 1986 and 1989 only gave tantalizing snapshots of these two cyan-colored worlds. Hubble and giant ground based telescopes continue picking up all kind of transitory cloud activities.
The most recent example is a pair of white spots that have popped up on Uranus. These could be towering methane anvil-shaped storms — the size of Texas — that are bursting high above Uranus’ cloud tops.
Though probably not funded until years into the future , Uranus and Neptune orbiters would see all sorts of intriguing and largely unexpected atmospheric displays.
In thinking about this, I would imagine that one of the first tasks of an alien interstellar probe visiting our solar system would be to dispatch nanosatellites to orbit all of the major planets and chronicle atmospheric dynamics.
Perhaps such alien relics would ultimately be abandoned in orbit. Or, more prudently, be deorbited into a planet’s atmosphere, as NASA did with their Galileo orbiter to Jupiter in 2003.
Image credit: NASA, L. Sromovsky