A new 3-D map shows ammonia swirling up to far below planet’s clouds
Jupiter, the largest planet in our solar system, is not a calm giant. It’s covered in swirling clouds that form colorful stripes and spots. Those cloud features include the famous Great Red Spot. It’s a storm wider than Earth —one that has been raging for several hundred years. Now scientists have discovered that Jupiter’s turbulence is not just skin deep. The storms and spots that we can see start far below the clouds.
Earth’s clouds are made of water vapor. Jupiter’s, in contrast, are mostly ammonia. And Jupiter’s atmosphere is always changing. That could give scientists a window into how the planet works inside. “One of the big questions is what is driving that [atmospheric] change,” says Leigh Fletcher. He’s a planetary scientist at the University of Leicester in England. “Why does it change so rapidly?” he asks. And how do those changes affect Jupiter’s environment and climate?
To address some of those questions, scientists have been studying Jupiter with an observatory called the Very Large Array in New Mexico. Among those researchers is Imke de Pater. He is a planetary scientist at the University of California, Berkeley. The Very Large Array measures a form of energy called radio waves. Jupiter gives off radio waves because it’s still cooling off from its birth about 4.6 billion years ago. Some of those waves get trapped by ammonia gas in Jupiter’s atmosphere before leaving the planet. Other waves travel through space all the way to Earth. By mapping what absorbs those radio waves, and where, the researchers created a three-dimensional (3-D) map of the ammonia beneath Jupiter’s clouds.
The scientists saw a chain of tall gas plumes. Each plume stretched nearly 100 kilometers below the cloud layer. These plumes carry ammonia upward to form ice clouds. Dry air sinks back down between the plumes. The updrafts and downdrafts seem to be powered by a narrow wave of gas that wraps around much of the planet. And the Great Red Spot, they saw, reaches at least dozens of kilometers below the clouds. The researchers reported their findings in the June 3 Science.
The depth of Jupiter’s turbulence isn’t too surprising, says Scott Bolton. He’s a planetary scientist at the Southwest Research Institute in San Antonio, Texas. “Almost everyone I know would have guessed that,” he says.
But the new observations do hint at what NASA’s Juno mission might find. Juno is a spacecraft due to reach Jupiter on July 4. Then it will start a 20-month investigation of what’s going on beneath Jupiter’s clouds. It will be using tools similar to those used in this study.
Bolton is leading the Juno mission. The new observations confirm that Juno should work as planned, he says.
Juno will get close to the planet — just 5,000 kilometers above the cloud tops. That will let it sneak inside belts of radiation around Jupiter. That radiation makes it hard to study the planet from Earth, and limits what telescopes like the Very Large Array can see.
But the spacecraft will see only a narrow piece of giant Jupiter at a time. “That’s where ground-based work like the research de Pater has been doing is really essential,” Fletcher says. Observations such as these will let Juno scientists know what’s going on throughout the atmosphere. That way, they can better understand what the spacecraft is telling them about this stormy giant.
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ammonia A colorless gas with a nasty smell. Ammonia is a compound made from the elements nitrogen and hydrogen. It is used to make food and applied to farm fields as a fertilizer. Secreted by the kidneys, ammonia gives urine its characteristic odor. The chemical also occurs in the atmosphere and throughout the universe.
atmosphere The envelope of gases surrounding Earth or another planet.
electromagnetic spectrum The range of radiation that spans from gamma- and X-rays through visible light and on to radio waves. Each type of radiation within the spectrum typically is classified by its wavelength.
Jupiter (in astronomy) The solar system’s largest planet, it has the shortest day length (10 hours). A gas giant, its low density indicates that this planet is composed of light elements, such as hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).
observatory (in astronomy) The building or structure (such as a satellite) that houses one or more telescopes.
planetary science The science of other planets besides Earth. A person who works in this field is known as a planetary scientist.
radiation (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
radio waves Waves in a part of the electromagnetic spectrum; they are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals; it is also used in radar.
turbulence The chaotic, swirling flow of air. Airplanes that run into turbulence high above ground can give passengers a bumpy ride.
water vapor Water in its gaseous state, capable of being suspended in the air.
Read another version of this story at Science News.
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Original Journal Source: I. de Pater et al. Peering through Jupiter’s clouds with radio spectral imaging. Science. Vol. 352, June 3, 2016, p. 1198. doi: 10.1126/science.aaf2210.