The Strange, Ferocious Extreme Weather of Our Solar System's Planets

Jonathan Belles
Published: June 8,2017

This enhanced color view of Jupiter’s cloud tops was processed by citizen scientist Bjorn Jonsson using data from NASA's JunoCam on the Juno spacecraft. A counterclockwise rotating storm appears as a white oval in the gas giant's southern hemisphere.
(NASA/JPL-Caltech/SwRI/MSSS/Bjorn Jonsson)

Storms on other planets are known to be mysterious, swirling and exploding pockets of gas that scream along faster than most, if not all, storms we see on Earth.
Only recent history and new technology have told us what our planetary neighbors are really like. We've learned Earth is not the only planet with blue skies, and other planets have hurricanes with eyes.
Similarities to Earth don't end there. Numerous planets exhibit a varying amount of Hadley cells with bands of stormy and clear skies, and large contrasts in their appearance. Water-ice has been found by spacecraft in the atmospheres. Astronomers have also found cirrus and banded stratus clouds similar to those here at home.
But there are also stark differences. Winds are far stronger on most planets and rain on the outer planets is made of diamonds.
To truly understand weather on other planets in the solar system, we must start at home.

Earth

In many ways, our weather is unique in part because we have a water planet and a different chemical composition than others. But in other ways, our planet is only unique because of our limited knowledge of the rest of the solar system.
On Earth, we have weather-makers from the size of tornadoes to monster hurricanes that are constantly monitored.
Tornadoes

• Size: From a few yards to more than two miles wide.
• Winds: Up to 300 mph, possibly higher.

Storms

• Winds: generally less than 50 mph, with some exceptions, like strong tropical cyclones and exceptionally strong polar storms. The strongest storms can have winds exceeding 200 mph.
• Precipitation and threats: water rain, ice and snow, high winds, lightning, tornadoes and a surge of water around our oceans.
• Size: tens of miles to 1,000 miles across.

A wide variety of storms circle Earth at a given time. We have storms that feed off both the warm oceans and temperature changes over land.

Visible satellite image from 3 p.m. EDT on June 6, 2017.

Note: Storms from this point on may be either high- or low-pressure systems.

Mercury

Due to the lack of a thick atmosphere, Mercury does not have storms or even clouds.

Venus

• Winds: 225 mph; these highest winds, which are a little stronger than the strongest hurricanes on Earth, are found 30 miles above the surface, but winds near the surface are nearly calm due to immense pressure.
• Precipitation: Sulfuric acid rain; this likely falls as virga and evaporates before it reaches the surface due to the extreme heat.
• Other Hazards: Lightning is infrequent and likely hotter than on Earth. Volcanic lightning may also be possible, if not common.
• Size: Four times larger than similar polar storms on Earth.

At both poles, two centers of circulation are found in large ever-morphing vortices. Why there are two centers at each pole is not well understood, but cycling hot air likely creates these polar storms.

Animation constructed from infrared images obtained over six consecutive days, showing the motion of the South Polar Vortex of Venus around the pole at the upper clouds altitude level, about 39 miles above the surface.

Venus has a nearly vertical axis, which means seasons are not as sensible as on Earth. Venus has a three-degree tilt versus Earth's 23.5-degree tilt.
Venus is unique in our solar system in that its day, the time it takes to make one rotation around its axis, takes longer than its trip around the sun.
The thick atmosphere of Venus is consists of carbon dioxide with clouds made of sulfuric acid. These greenhouse gases help to trap heat near the surface, which warms the rocky ground to more than 875 degrees.
Venus appears bright due to the clouds these gases create, but it looks very different from inside those clouds. Exploration by unmanned missions to Earth's sister has revealed the skies look orange, while its appearance from Earth is yellowish or greenish.
These gases also keep the temperature fairly constant from day to night and from one day to the next, since sunlight cannot penetrate the thick atmosphere.

Mars

Dust Devils

Smaller whirls of air akin to Earth's dust devils have been spotted on Mars by NASA's planetary rovers and orbiters in recent years, but not much is known about their formation or strength. It's believed they are created by heating from the sun, but other factors could also be involved.
Martian dust devils may be of similar shape and strength to their counterparts on Earth, but they may be much taller – possibly taller than 60,000 feet.
Dozens of dust devils have been spotted by the rovers Spirit and Opportunity over the last decade.

Storms

• Winds: Top speeds of 60 mph, or less than hurricane-force on Earth.
• Precipitation: Mainly windblown dust and sand.
• Rainfall: Although scientists think it used to rain, it doesn't rain on Mars today.
• Snowfall: Scientists at NASA have discovered it snows carbon dioxide ice crystals on Mars' southern pole, and while that snow accumulates, scientists aren't sure if it falls out of the sky or if it grows and accumulates from the air at the surface. It is possible snow could precipitate from clouds like here on Earth. Carbon dioxide ice, or dry ice, requires temperatures of about minus 193 degrees Fahrenheit to fall, which occurs on occasion at the poles. Water-ice snow has also been spotted at the Martian north pole.
• Size: One thousand miles to global scale.

Storms on Mars have a great range of sizes and shapes. Polar storms, like this one pictured in 1999, are similar to those on Earth, albeit slightly larger, with storms larger than the state of Texas.
Unlike Earth, dust storms can encircle the entire planet, but how this occurs is still being researched.
(WATCH: Mars Not Only Had Oceans, But Tsunamis)
Regional dust storms are common on Mars and generally happen every few weeks or months. Two such storms are shown below in the lighter brown colors are the bottom of the satellite imagery.

A global map of Mars with atmospheric changes from Feb. 18, 2017 through March 6, 2017, a period when two regional-scale dust storms appeared. It combines hundreds of images from the Mars Color Imager camera on NASA's Mars Reconnaissance Orbiter.

With multiple rovers and at least one weather-observing satellite, much research is being done on the weather and climate of Mars. Patterns are being recognized by Mars meteorologists and we are learning and being able to loosely predict Martian weather patterns.

Jupiter

• Winds: Up to 425 mph, or more than twice as strong as Earth's tropical cyclones.
• Precipitation: Helium and diamond rain.
• Storm size: Large enough to contain two Earths.

Jupiter is best known for the Great Red Spot, a high-pressure system that has raged for at least 300 years. This famous storm takes six days to completely rotate due to its large size. However, the Great Red Spot is slowly shrinking — a trend seen since the late 1800s, according to NASA.
The spot is thought to be an upper atmospheric system, unlike hurricanes on Earth, but has a relatively calm core like a hurricane's eye.
The reddish color of the spot comes from an unknown source low in the atmosphere of Jupiter. Some other storms harness a white hue thought to be ammonia.
Larger storms are known to eat smaller storms and other features as the storms move around the planet.
Red-orange and white clouds form bands on Jupiter's surface with alternating rising and sinking motions, similar to Hadley cells on Earth, although there are far more bands on Jupiter.
(MORE: Great Red Spot Heating Jupiter's Atmosphere to 2,500 Degrees, Study Says)
Earth-sized cyclones also orbit around Jupiter's poles, according to recent imagery from the JunoCam. These cyclones often run together and bounce off each other.
Jupiter is mainly heated from the inside through convection of liquid and plasma since the planet is too far away from the sun to receive appreciable heating at its gaseous surface. The biggest gas giant is mainly made up of hydrogen and some helium.

This image shows Jupiter’s south pole from an altitude of 32,000 miles. The oval features are cyclones, up to 600 miles in diameter. Multiple images taken with the JunoCam instrument on 3 separate orbits.
(NASA/Juno)

Saturn

• Winds: More than 1,100 mph in the upper atmosphere, or about four times faster than the strongest jet streams on Earth.
• Precipitation: liquid diamonds.
• Other hazards: solid diamonds bouncing around in the upper atmosphere may lead to explosive lightning.
• Storm size: Thunderstorms in Saturn's mid-latitudes can grow to 8,000 miles, the diameter of Earth, every couple of decades. These "Great White Spots" can act like atmospheric comets that encircle the planet with relatively dry convective tails of disturbed weather. These storms may be made of ammonia, which condenses near the top of Saturn's troposphere, the weather part of the atmosphere. Water vapor may keep the frequency of these spots low.

Saturn's façade is marked by numerous stripes of clouded and cloudless skies. Cloud bands move around Saturn's atmosphere at varying speeds, which often causes areas of spin between bands where storms can develop.

In contrast to every other planet, Saturn has a hexagonal jet stream pattern at the northern polar region.

This colorful view from NASA's Cassini mission is the highest-resolution view of the unique six-sided jet stream at Saturn's north pole known as "the hexagon."

(MORE: Spotted on Saturn: Hexagon-Shaped Jet Stream Encircling a Storm)
A hurricane-like feature is locked above Saturn's north pole with winds of 330 mph. The system has an eye more than 50 times larger than the eye of hurricanes on Earth. If the Saturn hurricane formed on Earth, everyone from New York City to Miami would fit in its eye. Winds spin counter-clockwise, like hurricanes in Earth's northern hemisphere.
There is a similar but weaker cyclone that spins in the opposite direction in the Southern Hemisphere.
Much of Saturn's atmosphere is made of hydrogen and helium. Bands in Saturn's atmosphere also contain sulfur, methane, ammonia, nitrogen and oxygen.

Uranus

• Winds: 560 mph, or about twice as fast as on Earth; winds blow in the opposite direction of the planet's rotation.
• Precipitation: diamonds.
• Storm size: 5,760 miles, or about the distance from Los Angeles to Tokyo; this is according to measurements from the Hubble Space Telescope, but storms may be larger.

The weather largely depends on which pole is facing the sun since Uranus is tilted on its side. For half of the planet’s 84-year orbit, the north pole faces the sun, and during the other half, the south pole faces the sun. The other half of the planet is in complete darkness.
On any planet closer to the sun, the most violent weather would occur near the most heated part of the planet, but this isn't where most of the weather occurs for planets in the outer solar system.
Since Uranus is sideways, it receives most of its sunlight at its poles. The core of Uranus heats the equator more than the poles, and this drives weather on the seventh planet from the sun. At this distance, the sun doesn't do much to heat the planet.
(WATCH: Giant Methane Storms On Uranus)
In some places, temperatures drop below minus 370 degrees – even colder than Neptune, in some places.
Recently, the weather has been active near the equator of Uranus, with eight large storms detected in August 2014.
Saturn's weather (or Hadley cells) are driven by the planet’s relatively warm core. Gases and clouds rise and sink in bands as the air cools, creating cloudless skies. These alternating bands also move in opposite directions.
Scientists have watched areas of circulating clouds and thunderstorm features near the north pole for more than a decade.
Thunderstorms track by using bright cloud tops made of methane ice. Methane gives Uranus its dull blue color, but hydrogen and helium make up larger portions of the atmosphere, with trace portions of water and ammonia.

Infrared images of Uranus obtained on Aug. 6, 2014 on the 10-meter Keck II telescope. The white spot is an extremely large storm that was brighter than any feature ever recorded on the planet.
(Imke De Pater (UC Berkeley) and W. M. Keck Observatory)

Neptune

• Winds: can exceed 1,100 mph at high altitudes, or one and a half times the speed of sound, which makes these winds supersonic.
• Precipitation: Methane and carbon diamonds, likely in liquid form.
• Storm size: The Great Dark Spot was a little bigger than the diameter of Earth, or just over 8,000 miles. The new dark spot is roughly 3,000 miles, or three times larger than Earth's largest storms.

The Great Dark Spot, a cyclone bigger than the size of Earth, rotated counter-clockwise and moved westward at 750 mph. That cyclone was spotted in the 1980s and 1990s by Voyager 2 and the Hubble Space Telescope. Scientists are unsure if this storm still exists.
Imagery of Neptune has been scarce due to its distance, but in 2016, the Hubble Space Telescope turned its gaze toward the planet again.
A new dark spot, thought to be a high-pressure system, was found in Neptune's southern hemisphere in 2015 and 2016. The bright clouds are thought to be similar to lenticular or pileus clouds on Earth but are made of methane ice crystals.
(MORE: Neptune's Huge Dark Vortex Seen by NASA for First Time This Century)
Ammonia, hydrogen sulfide and water-ice clouds may also exist at lower elevations.
This feature is thought to last years but is not expected to last as long as Jupiter's Great Red Spot – also a high-pressure system.

Hubble Space Telescope imagery confirms a dark vortex in the atmosphere of Neptune. The image (left) shows that the dark feature resides near/below a patch of bright clouds in the planet's southern hemisphere. The top image is a close-up of the feature.
(NASA)

Other faster but smaller features have been spotted rapidly moving through the atmosphere. One such feature, called scooter due to its fast forward speed, is likely made up of frozen clouds similar to cirrus on Earth.
The atmosphere consists of hydrogen and helium and higher amounts of methane than Uranus, giving it a brighter blue color.
At least two cloud decks and long cloud streaks 31 miles high have been observed.
Weather on Neptune is driven by heating at the core of the gas planet rather than from sunlight.

What About Pluto?

The recent flyby of the New Horizons spacecraft is re-writing textbooks about the dwarf planet. This science is quickly evolving and is largely still being figured out, but we've learned the atmosphere has greatly changed over Pluto's history, and we know skies on Pluto are also blue.
(MORE: Pluto Has Tropic and Arctic Regions, New Horizons Scientists Say)

MORE: Images of Saturn

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