Other Worlds, Other Storms
by Patricia d. Lock
Weather is everywhere! We live in it every day, and with weather come storms. What you may not realize, though, is that our neighboring planets and moons have weather and storms much as we do.
We call the study of the planets in relation to each other comparative planetology. The field looks at the different natures of the planets and moons in our solar system to help understand the origin, history, and future of our own planet. Atmospheric scientists study the composition, structure, and motions of atmospheres, both on Earth and off.
“The planets can be thought of as ‘weather’ laboratories, in which different climatic changes and weather occur naturally because the planets have different atmospheres, different surfaces, and different amounts of sunlight,” says atmospheric scientist Dr. Richard Zurek. “All of this gives us a new perspective on the weather and climate of our own planet. The same forces are at work, but in different proportions.”
Planetary Weather Forecasts
- Mercury's weather forecast would be rather like one for the moon. Nothing, nothing, nothing. Its high temperature of greater than 750 degrees F does not allow a permanent atmosphere and, therefore, any weather.
- Venus—Cloudy and hot.
- On Venus, the forecast is cloudy with a high of 840 degrees F. The chance of a breeze is zero percent, with weather at the equator being the same as that at the poles. The sky looks as if a storm is coming, but there are no storms, hurricanes, tornadoes, or jet streams.
- Mars—Cool and windy. Leave the dusting for tomorrow.
- Mars is a bit more hospitable, with sunny days and cool nights. The average temperature is minus 67 degrees F, with lows of minus 207 degrees F in winter and occasional summer highs of a pleasant 80 degrees F. The seasons on Mars are longer than Earth's, as its year is 687 Earth-days long. The most interesting weather on Mars is its huge dust storms. In 2001, a storm raised a cloud of dust that engulfed the entire planet for three months.
- Jupiter—Cloudy with a chance of thunder and lightning.
- Jupiter's weather, while beautiful from a distance, would be rather turbulent for the visitor. The temperature at the top of Jupiter's ammonia clouds is minus 227 degrees F, and winds reach 400 miles per hour. Huge thunderstorms cause lightning over areas the size of the United States. Some of the largest thunderstorms are 50 miles tall and 2,500 miles wide.
- In 2000, scientists watched two of Jupiter's “white oval” storms, each about half the size of Earth, collide and merge to form an even bigger storm. Researchers think that a similar event built Jupiter's Great Red Spot, a storm twice as wide as the Earth that has lasted for more than 300 years.
- Saturn—Windy and cold; winds dropping later.
- Just north of its equator, Saturn's clouds move at more than 1,000 miles per hour, with temperatures of minus 310 degrees F. Saturn's storms behave a lot like the storms on Earth: They are influenced by jet streams and travel large distances, and many are the size of our hurricanes. Saturn recently had an unexpected change in its weather: Winds near the equator slowed from about 1,050 to 600 miles per hour. Saturn's long year, about 30 Earth-years, and the shadow from its rings could possibly account for this change.
- Uranus—Spring is in the air!
- With a “tilt” of almost 90 degrees and a year lasting roughly 84 Earth-years, Uranus has seasons that last for 20 years. The northern hemisphere of Uranus is just now coming out of winter, and huge storms and temperatures of minus 300 degrees F are battering the planet. The hemisphere facing away from the sun is in darkness the entire season.
- Neptune—Stormy and cold, high winds for the rest of the season.
- Neptune is also coming into a spring period, with the change in sunlight causing its cloud bands to get wider and brighter. Massive storm systems have winds that reach 900 miles per hour and temperatures of minus 350 degrees F. Like Uranus's, Neptune's seasons last for decades because its year lasts almost 165 Earth-years. It is remarkable that Neptune exhibits any seasonal change at all, because the sun is 900 times dimmer there than it is on Earth.
- Pluto—Skating, anyone?
- Spacecraft have visited all of the planets except Pluto. With our limited knowledge of it, weather prediction is, at best, a wild guess. The temperature is also a guess, but scientists believe it to be around minus 385 degrees F. It is so cold during the 100 years when Pluto is farthest from the sun that even nitrogen, carbon monoxide, and methane gases freeze onto its surface.
Learning From Our Neighbors
What have we learned? A lot! “Mars told us that there can be global dust storms, and that got people to think about what might happen if an asteroid collided with Earth and threw a massive dust cloud into the atmosphere,” Zurek explains. “Venus tells us that if you have too much carbon dioxide, you can get a runaway greenhouse effect in which the surface becomes very hot.”
According to Zurek, we also know now that Mars is the planet most like the Earth, in that it has a relatively thin atmosphere, has seasons like the Earth, has a day that is just a little longer than ours, and also uses sunlight as its principal energy source. Mars also has a surface temperature that, while cold, is closest to that of Earth.
Where To, Next?
In 2004, the Cassini spacecraft began an in-depth study of the Saturn system and landed a probe on its moon, Titan. Two rovers, two orbiters, and a lander are on their way to Mars. In 2005, an orbiter was launched to make daily weather maps of the Red Planet. (Zurek is the Project Scientist for this mission, the Mars Reconnaissance Orbiter.) There are also plans to revisit Jupiter's moons this decade, and to visit Pluto by 2020.
“It takes a long time to do a space mission, and you always wish you knew more so that you could design the systems better,” Zurek says. “But we make progress step by step.”
So stay tuned for the next storm watch from other worlds.
- Why do you think scientists want to make daily weather maps of Mars? What might be the benefit of making these maps? Write a few sentences to explain your answer.
- Draw a picture showing what it might look like if you were standing on the surface of Jupiter in the middle of the Great Red Spot. What would you see? How would the storm affect the planet's surface?