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Alien Storms

by Perry Pezzolanella

Hurricane Sandy was classified as a super storm when it ravaged the eastern U.S. in late October 2012, but this storm is nothing like the storms on other worlds. Hurricanes larger than Earth raging for centuries, lightning capable of vaporizing a city, winds howling at twice the speed of sound, rain falling at -300ºF, and lightning flashing in blistering hot acid skies make Sandy appear tame. This weather really does occur, but fortunately not on Earth.

There is no comparison between Sandy and Jupiter’s Great Red Spot. This storm is twice the size of Earth and has winds about 400 miles per hour. It has been raging for at least 340 years, since it was first seen with a telescope, and may have been around longer. There is no solid surface on Jupiter to tear apart the Great Red Spot, which is steadily fed by the heat from far below and is the highest cloud feature on Jupiter. The reddish color is probably due to phosphine. It has changed shape through the centuries and has shrunk and faded, but shows no signs of dying. Jupiter has the most powerful lightning of all the planets with a single flash that can span Asia and enough power to vaporize a city. Jupiter is clearly the King of Storms.

Saturn is farther from the Sun and colder than Jupiter, but much windier with winds up to 1000 miles per hour. The winds blow the opposite direction from the planet’s rotation, which causes the currents to create a bizarre storm system. Clouds resembling smoke rings form in the retrograde jet stream. The middle of one of these jet streams is known as Thunderstorm Alley where there is a series or chain of ferocious thunderstorms loaded with lightning. At times a huge plume of methane and ammonia erupt from far below and creates a huge thundercloud anvil of bright white ammonia ice. The Great White Spot of 1990 was so huge and bright that this author followed it for weeks during that October and November using only an 80mm (3.1”) refractor. The big storm of 2011 was seen as an exceptionally bright belt contrasting with the rest of Saturn’s clouds. There is a lot of water deep within Saturn and it appears to be the main generator of the lightning. Internal heat from far below causes the moisture to rise and form clouds that grow high into the colder air aloft. Once the water begins to freeze and create ice particles, the strong winds and turbulence can make the particles collide and separate charges to cause lightning.

Uranus was a dull, quiet planet when Voyager 2 flew past it in late January 1986. The thick, cloudy atmosphere contains methane which gives Uranus a nice bluish color like Neptune, however, there is a ruddy haze that shifts the light toward green giving it more of a turquoise tint. Uranus was pole-on to the Sun in 1986 when Voyager 2 flew by but the equator faced the Sun in 2007 and the more uniform heating of the atmosphere has made it a very stormy planet. Huge clouds of methane erupt from below like Saturn and appear as white spots. Strong upper-level winds blow the tops of the clouds downwind making them look like tadpoles. Uranus is a frigid -330ºF but still capable of numerous storms and has taken on the appearance of Neptune. The storms may last up to a year but are hard to follow because only the Hubble Space Telescope and the Keck 10-meter Telescope have the power to resolve the clouds, and observing time is severely limited. Scientists are hoping for a return mission to Uranus but that will probably not happen in our lifetimes.

In any atmosphere there is always a battle between upwelling air currents that keep particles afloat and the force of gravity pulling the particle down. For clouds to form the particles must stay airborne long enough for condensation to occur which’ll grow into clouds large enough to be visible. If there are few particles, larger particles will condense and fall more rapidly forming fewer clouds. Neptune has a surprisingly clear but violently windy upper atmosphere. It is the windiest world of all with speeds up to 1400 miles per hour. It has more internal heat than Uranus so it is no colder even though it is a billion miles further away from the Sun than Uranus. Neptune may be so clear because methane condenses so rapidly and there is so much of it that in hardly a minute a little droplet grows to the size of a beach ball and falls as a giant raindrop. Giant methane raindrops as large as beach balls would fall too quickly to form clouds. It will require a probe descending through Neptune’s atmosphere to test this theory, but a return mission is most likely out of reach in our lifetimes.

Titan, the largest moon of Saturn, has a rainfall cycle similar to Earth. Deep in the orange smog, clouds boil upwards like they do on Earth and condense causing rain to fall on the icy land below. Flash floods race through the dry riverbeds carrying stones and organics towards the lowlands. The rain is actually frigid methane falling in the nearly -300ºF cold. The Cassini spacecraft has detected these storms and they may be prolific by dumping as much as 100 inches of rain in a few hours. The convection to produce these storms is vigorous enough to produce lightning, but so far there is no evidence of it.

Snow is common in the Earth’s colder climates and also occurs on Mars. The Phoenix lander and Mars Reconnaissance Orbiter have detected snowfall on Mars. The snow is a frigid mix of water and carbon dioxide and the storms that develop as winter sets in over the poles can deposit snow up to several feet deep. It is heavy enough that it actually broke off the solar panels on the Phoenix lander. Another type of storm on Mars is the infamous dust storm. These can grow so fast and huge that they can completely envelop the planet. The dust particles are blown in the thin atmosphere at speeds up to 200 miles per hour and are dry enough to potentially generate lightning. Mars is also home to giant dust devils that roam across the vast deserts. Most of them are innocent whirlwinds but a few can grow in size similar to tornadoes on Earth and just as dangerous.

Venus has a frightening and bizarre climate where the average surface temperature is 870ºF and air pressure 92 times Earth’s. It is blanketed by a thick carbon dioxide atmosphere and clouds all laced with sulfuric acid mist and it is very dry. The strong winds in the clouds where it falls below zero degrees are capable of separating charges and generating lightning. The lightning stays within the clouds as they are about 30 miles above the surface and too high for them to strike the surface. Most of the storms occur late in the afternoon and a rain of sulfuric acid falls from the clouds but evaporates long before reaching the surface due to the sizzling heat below.

There may be bad weather days on Earth, and historic storms do occasionally strike, but none can compare to the storms in the faraway alien skies of other worlds. All of them are extreme and deadly; brutal cold, sizzling heat, corrosive acid, choking dust, supersonic winds, and lightning superbolts. At least on Earth there are better odds of surviving a storm. Learning how storms on other worlds work will teach us how to predict them here on Earth and to be better prepared.