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NASA Spies Churning Waves of Ammonia in Jupiter’s Atmosphere

Astronomers peek below the clouds to produce the most detailed map yet.
Image: Radio: Michael H. Wong, Imke de Pater (UC Berkeley), Robert J. Sault (Univ. Melbourne). Optical: NASA, ESA, A.A. Simon (GSFC), M.H. Wong (UC Berkeley), and G.S. Orton (JPL-Caltech)

Jupiter has captivated onlookers for centuries with its giant red spot and turbulent sea of rolling clouds. However, much of Jupiter remains a mystery because of those same intriguing cloud layers. Now, just one month before NASA's Juno spacecraft is set to orbit the mighty gas giant, scientists got their first glimpse behind the curtain.

Scientists discovered massive waves of ammonia swirling deep within Jupiter's thick upper atmosphere. The findings, published this week in Science, provide new insight into the gas giant's dynamic and enigmatic atmosphere.

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Using the upgraded Very Large Array (VLA)—one of the world's premier radio telescopes—astronomers lifted the hazy veil and peered deep into Jupiter's atmosphere. Thanks to the telescope's sensitivity, a team of astronomers led by UC Berkeley, has mapped out Jupiter's atmosphere in unprecedented detail. Probing 60 miles (100 km) below the clouds, the team discovered a link between the swirling surface clouds and the churning gases below.

Image: Radio: Michael H. Wong, Imke de Pater (UC Berkeley), Robert J. Sault (Univ. Melbourne). Optical: NASA, ESA, A.A. Simon (GSFC), M.H. Wong (UC Berkeley), and G.S. Orton (JPL-Caltech)

"We in essence created a three-dimensional picture of ammonia gas in Jupiter's atmosphere, which reveals upward and downward motions within the turbulent atmosphere," lead author and UC Berkeley professor of astronomy Imke de Pater said in a statement.

It's known that Jupiter's clouds are composed of ammonia ice, but what's happening within those clouds has long puzzled astronomers. In the 1980's, astronomers used part of the present day VLA to measure the ammonia levels within Jupiter's atmosphere. Their findings showed that only trace amounts of the noxious gas was present. However, in 1995, when NASA's Galileo spacecraft plunged a probe into Jupiter's atmosphere, it told a very different story.

Descending more than 60 miles (100 km) before being crushed by the immense pressure and heat from Jupiter's atmosphere, Galileo detected ammonia levels four to five times higher than previous radio measurements. Scientists now think they can explain such a large discrepancy—Jupiter's thick atmosphere is concealing waves of ammonia that swirl around the planet.

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In 2014, de Pater and her team measured radio emissions from Jupiter across the 4 to 18 gigahertz range, creating a 3D map of Jupiter's upper atmosphere from the data. Following its upgrades, the VLA is about ten times more sensitive than before, so astronomers are working with a higher spatial resolution. This allows astronomers to better decipher the planet's fast-moving atmosphere.

"With radio, we can peer through the clouds and see that those hotspots are interleaved with plumes of ammonia rising from deep in the planet, tracing the vertical undulations of an equatorial wave system," said UC Berkeley research astronomer Michael Wong.

When analyzing the new radio maps, the team made an intriguing observation. Around the planet's equator, they spotted a series of puzzling dark and light patches, each measuring tens of thousands of kilometres across. Some of the dark patches were so large, they dwarfed Jupiter's famous great red spot.

These patches are key to understanding Jupiter's atmospheric processes, and provide insight into the amount of ammonia present. De Pater says that the dark patches are indicative of high levels of ammonia and by contrast, the bright white areas—known as hot spots—have low concentrations of the gas. However, it's not yet clear whether these patches are ubiquitous or exist solely around the equator.

Image: Radio: Michael H. Wong, Imke de Pater (UC Berkeley), Robert J. Sault (Univ. Melbourne). Optical: NASA, ESA, A.A. Simon (GSFC), M.H. Wong (UC Berkeley), and G.S. Orton (JPL-Caltech)

Alternating patches of ammonia hotspots could explain why the Galileo probe recorded higher than expected levels of the gas. But many more Jovian mysteries remain, including whether or not a deeper layer of water-rich clouds exists within Jupiter's atmosphere. Hydrogen and helium dominate the massive planet's atmosphere; however, trace amounts of water in addition to the ammonia have been detected.

Juno will begin orbiting Jupiter next month, on July 4, and part of its mission will involve looking for water in the same regions the VLA is searching for ammonia. "Maps like ours can help put their data into the bigger picture of what's happening in Jupiter's atmosphere," de Pater said.