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Study Helps Solve Mystery Under Jupiter’s Clouds

Scientists from Australia and the United States have helped to solve the mystery underlying Jupiter’s coloured bands in a new study in The Astrophysical Journal (https://goo.gl/jDc9BR) on the interaction between atmospheres and magnetic fields.

Jupiter is a gaseous planet consisting mostly of hydrogen and helium. Several strong jet streams flow west to east in Jupiter’s atmosphere that are, in a way, similar to Earth’s jet streams. Clouds of ammonia at Jupiter’s outer atmosphere are carried along by these jet streams to form Jupiter’s coloured bands, which are shades of white, red, orange, brown and yellow. Until recently, little was known about what happened below Jupiter’s clouds.

“We know a lot about the jet streams in Earth’s atmosphere, and the key role they play in the weather and climate, but we still have a lot to learn about Jupiter’s atmosphere,” said co-author Dr Navid Constantinou of The Australian National University. “Scientists have long debated how deep the jet streams reach beneath the surfaces of Jupiter and other gas giants, and why they do not appear in the Sun’s interior.” Recent evidence from NASA’s Juno spacecraft indicates the jet streams reach as deep as 3000 km below Jupiter’s clouds.

The research involved mathematical calculations for the instability that creates jet streams when magnetic fields are present, and compared theoretical predictions with results from previous computer simulations. From this the researchers concluded that Jupiter’s jet streams are suppressed by a strong magnetic field. “The gas in the interior of Jupiter is magnetised, so we think our new theory explains why the jet streams go as deep as they do under the gas giant’s surface but don’t go any deeper,” said co-author Dr Jeffrey Parker from the Lawrence Livermore National Laboratory.

The polar and subtropical jet streams in Earth’s atmosphere shape the climate, especially in the mid-latitudes such as in Australia, Europe and North America. “Earth’s jet streams have a huge impact on the weather and climate by acting as a barrier and making it harder for air on either side of them to exchange properties such as heat, moisture and carbon,” Constantinou said.

The jet streams on Earth are wavy and irregular, while they are much straighter on Jupiter. “There are no continents and mountains below Jupiter’s atmosphere to obstruct the path of the jet streams,” Parker added. “This makes the jet streams on Jupiter simpler. By studying Jupiter, not only do we unravel the mysteries in the interior of the gas giant, but we can also use Jupiter as a laboratory for studying how atmospheric flows work in general.”