For the last decade, astronomers have observed curious “hotspots” on Saturn’s poles. In 2008, NASA’s Cassini spacecraft beamed back close-up images of these hotspots, revealing them to be immense cyclones, each as wide as the Earth. Scientists estimate that Saturn’s cyclones may whip up 300 mph winds, and likely have been churning for years.

While cyclones on Earth are fueled by the heat and moisture of the oceans, no such bodies of water exist on Saturn. What, then, could be causing such powerful, long-lasting storms?

In a paper published today in the journal Nature Geoscience, atmospheric scientists at MIT propose a possible mechanism for Saturn’s polar cyclones: Over time, small, short-lived thunderstorms across the planet may build up angular momentum, or spin, within the atmosphere — ultimately stirring up a massive and long-lasting vortex at the poles.

The researchers developed a simple model of Saturn’s atmosphere, and simulated the effect of multiple small thunderstorms forming across the planet over time. Eventually, they observed that each thunderstorm essentially pulls air towards the poles — and together, these many small, isolated thunderstorms can accumulate enough atmospheric energy at the poles to generate a much larger and long-lived cyclone.

The team found that whether a cyclone develops depends on two parameters: the size of the planet relative to the size of an average thunderstorm on it, and how much storm-induced energy is in its atmosphere. Given these two parameters, the researchers predicted that Neptune, which bears similar polar hotspots, should generate transient polar cyclones that come and go, while Jupiter should have none.

Morgan O’Neill, the paper’s lead author and a former PhD student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), says the team’s model may eventually be used to gauge atmospheric conditions on planets outside the solar system. For instance, if scientists detect a cyclone-like hotspot on a far-off exoplanet, they may be able to estimate storm activity and general atmospheric conditions across the entire planet.

“Before it was observed, we never considered the possibility of a cyclone on a pole,” says O’Neill, who is now a postdoc at the Weizmann Institute of Science in Israel.

“Only recently did Cassini give us this huge wealth of observations that made it possible, and only recently have we had to think about why [polar cyclones] occur.”

O’Neill’s co-authors are Kerry Emanuel, the Cecil and Ida Green Professor of Earth, Atmospheric and Planetary Sciences, and Glenn Flierl, a professor of oceanography in EAPS.

Beta-drifting toward a cyclone

Polar cyclones on Saturn are a puzzling phenomenon, since the planet, known as a gas giant, lacks an essential ingredient for brewing up such storms: water on its surface.

“There’s no surface at all — it just gets denser as you get deeper,” O’Neill says. “If you lack choppy waters or a frictional surface that allows wind to converge, which is how hurricanes form on Earth, how can you possibly get something that looks similar on a gas giant?”

The answer, she found, may be something called “beta drift” — a phenomenon by which a planet’s spin causes small thunderstorms to drift toward the poles. Beta drift drives the motion of hurricanes on Earth, without requiring the presence of water. When a storm forms, it spins in one direction at the surface, and the opposite direction toward the upper atmosphere, creating a “dipole of vorticity.” (In fact, videos of hurricanes taken from space actually depict the storm’s spin as opposite to what’s observed on the ground.)

“The whole atmosphere is kind of being dragged by the planet as the planet rotates, so all this air has some ambient angular momentum,” O’Neill explains. “If you converge a bunch of that air at the base of a thunderstorm, you’re going to get a small cyclone.”

The combination of a planet’s rotation and a circulating storm generates secondary features called beta gyres that wrap around a storm and essentially split its dipole in half, tugging the top half toward the equator, and the bottom half toward the pole.

The team developed a model of Saturn’s atmosphere and ran hundreds of simulations for hundreds of days each, allowing small thunderstorms to pop up across the planet. The researchers observed that multiple thunderstorms experienced beta drift over time, and eventually accumulated enough atmospheric circulation to create a much larger cyclone at the poles.

“Each of these storms is beta-drifting a little bit before they sputter out and die,” O’Neill says. “This mechanism means that little thunderstorms — fast, abundant, but not very strong thunderstorms — over a long period of time can actually accumulate so much angular momentum right on the pole, that you get a permanent, wildly strong cyclone.”

Next stop: Jupiter

The team also explored conditions in which planets would not form polar cyclones, even though they may experience thunderstorms. The researchers found that whether a polar cyclone forms depends on two parameters: the energy within a planet’s atmosphere, or the total intensity of its thunderstorms; and the average size of its thunderstorms, relative to the size of the planet itself. Specifically, the larger an average thunderstorm compared to a planet’s size, the more likely a polar cyclone is to develop.

O’Neill applied this relationship to Saturn, Jupiter, and Neptune. In the case of Saturn, the planet’s atmospheric conditions and storm activity are within the range that would generate a large polar cyclone. In contrast, Jupiter is unlikely to host any polar cyclones, as the ratio of any storm to its overall size would be extremely small. The dimensions of Neptune suggest that polar cyclones may exist there, albeit on a fleeting basis.

“Saturn has an intense cyclone at each pole,” says Andrew Ingersoll, professor of planetary science at Caltech, who was not involved in the study. “The model successfully accounts for that. Jupiter doesn't seem to have polar cyclones like Saturn's, but Jupiter isn't tipped over as much as Saturn, so we don't get a good view of the poles. Thus the apparent absence of polar cyclones on Jupiter is still a mystery.”

The researchers are eager to see whether their predictions, particularly for Jupiter, bear out. Next summer, NASA’s Juno spacecraft is scheduled to enter into an orbit around Jupiter, kicking off a one-year mission to map and explore Jupiter’s atmosphere.

“If what we know about Jupiter currently is correct, we predict that we won’t see these wildly strong cyclones,” O’Neill says. “We’ll find out next year if our predictions are true.”

This research was funded in part by the National Science Foundation.

"A Theory of the Relativistic FermionicSpinrevorbital" as published atwebsite: http://www.academicjournals.or... gives a prior theory of the dynamics determined by this model wherebymany smaller thunderstorms of weaker internal momenta (reactants) undergotransformations forming a more powerful cyclone of stronger momenta (product). For free copy click "full text PDF". On page 2 the Lawsof Ferrochemistry are given. The "Second Law of Ferrochemistryinvolves Little Rule 1 and involves that the coupling relationships betweensystems of physicochemical reactions and itself internally and/or the minimumneeded external magnetic field and/or external spin0 revolution-orbital(spinrevorbital) matter, energy, momentum, density and/or acceleration to alterdynamics and kinetics of the system of physicochemical reaction are such thatthe greater the energy of the physicochemical reactants in space time then theeasier and inherent the internal coupling of the spinrevoritals of the multiplereactants and/or the smaller the minimum needed external magnetic field and/orspinrevorbitals' energy and momentum density in surrounding space time tocouple with the physicochemical reactions and alter the course (dynamics) andrates (kinetics) of the physicochemical reactions." By this Rule 1[of Law 2] the stronger thunderstorms in Saturn can couple to weaker rotationfield even Saturn's rotation about its axis. The Earth's thunderstormsare weaker and couple less so relative to Saturns' thunderstorms. Thereby thethunderstorms on earth do not separate their top and bottoms to the same extentfor bottom to go to poles and top of storm to migrate to equator as they do onSaturn. But such on earth is seen as the positive part (top) of thunderstormoften lags the bottom negative biased part of thunderstorms on earth! Moreover I give the Law for why the large cyclone forms on Saturn but noton Neptune or Jupiter as in Little Rule 2 for the Third Law of Ferrochemistryinvolving Little Rule 2. "The Third Law of Ferrochemistry involvesLittle Rule 2 (2000) and considers that for systems of small particle densitiesand high internal magnetic fields in the presence (internally or externally) ofsufficiently strong magnetic field and/or sufficiently large energy spinrevolutionary orbital (spinrevorbital) energy, matter, momenta, density,acceleration and momenta beyond the coupling strength by Law 2 then thephysicochemical reaction dynamics is either altered such that the spinrevorbitalmomenta of the products are larger than spinrevorbital momenta of reactants inthe slow rotational limit of the activating conditions or the physicochemicalreaction dynamics is altered such that the spinrevorbital momenta of theproducts are smaller than the spinrevorbital momenta of the reactants in thefast rotational limit of the activating conditions. " By this ThirdLaw for Little Rule 2 the thunderstorms of Saturn (reactants) have smallermomenta and transform to the polar cyclone (product) of larger momentum in theslow rotational limit of Saturn's relatively slow planetary rotation! TheLaws of Ferrochemistry and the Little Rules as outlined here by RBL give asolid foundation for these simulations of Saturn! I will not state Law 4of Little Rule 3 but it applies more to conditions on the earth and it gives abasis for why the thunderstorms on earth do not separate and form strongerpolar vortex at the poles of the earth. During the winter the drop intemperatures may allow transient vortex to form near the earth's poles whichrapidly reverses to drift toward the equator of the earth to explain the recentpolar vortex and extreme winter cold in USA during winter of 2013 relative to asummer thunderstorm of higher temperature splitting to have its bottom driftnorth to the north pole! But back to the article In the next paragraph Ieven give the boundary conditions for the Rule 2 as applies to Saturn (withidentical to the size and energy restriction given by the MIT researchers). I state "systems of fewer atoms tend to behave by Rule 2 over longtime and they behave by Rule 3 over shorter times. Systems of largerenergy tend to behave by Rule 2 over longer times and they behave by Rule 3over shorter times." "Rule 2 applies to parts of larger systems,higher energies and orbitals in smaller systems." Such parts oflarger systems, higher energies (for larger thunderstorm size to planetarysize) is identical to the conditions of large size of the storm relative tosize of the planet and higher energy of the storm for Rule 2 on Saturn. But the weaker energy storms on Jupiter of smaller size relative to thewhole planet Jupiter more appropriately are describe by Rule 3 which"applies to while structures , lower energies and orbits! This isvery powerful and beautiful, broad, deep and consistent. Although in thepaper I do not directly point and illustrate these laws to Saturn and Jupiter. I do allude to novel magnetogravity driven chemistry by such effects inSaturn and Jupiter on page 14. On page 14 by these dynamics I describethe atmospheres of Saturn and Jupiter as liquid crystalline! In the wholeframe of this paper I discover a way to unify gravity and magnetism and generaltheory and quantum mechanics. By my unification the liquid crystallinityof the atmosphere of Saturn emerges. I note the high pressures and lowtemperatures involve a transformation of heat to pressures to electric togravity in the Saturn and Jupiter for a strong gravitational force withmagnetism to bind atoms! I note here that such magneto-gravitationalchemical bonding in Saturn manifest the crystallinity of its atmosphere as thehexagonal shape of its polar cyclone! This is very powerful and beautifuland I thank GOD for the vision! RBL

Reprinted with permission of MIT News