While many people are preparing for the weekend holiday celebrations and observations, the planetary science world is still making amazing discoveries. We turn now to NASA’s Juno spacecraft. One of the primary goals of this mission is to gain a greater understanding of how the storms and cloud layers work beneath the surface. To that end, the spacecraft is equipped with a microwave radiometer.

This instrument is designed to measure microwave emissions from deep inside the planet, using wavelengths ranging from 1.4 centimeters to 50 centimeters. The corresponding atmospheric pressures are about 0.6 bars at the surface, which is less than the surface of Earth, and down past 100 bars or 250 kilometers beneath the cloud tops. Sometimes, you have to step outside visible light to find what you are looking for, and that’s what was done here.

When we look at Jupiter in visible light, we see a pattern of lighter zones and darker belts. You can observe this banding with a relatively small telescope even. Using microwaves, the zones appear bright while the belts stay dark. Brighter objects in these wavelengths are either warmer or lack ammonia, which tends to absorb microwave light. And down to five bars of pressure or five times the pressure at the Earth’s surface, this structure persists.

Then, at 10 bars, the entire pattern reverses. The darker zones are now bright in microwave light while the belts become dark. Something has to have changed, and it’s either the temperature or the abundance of ammonia. This region of transition between 5 and 10 bars is now called the “jovicline” because it’s similar to how seawater in our ocean’s thermocline transitions from relative warmth to colder water.

The results of this data analysis were published in the Journal of Geophysical Research: Planets, and lead author Dr. Leigh Fletcher explains: One of Juno’s primary goals was to peer beneath the cloudy veil of Jupiter’s atmosphere and to probe the deeper, hidden layers. Our study has shown that those colorful bands are just the ‘tip of the iceberg’ and that the mid-latitude bands not only extend deep but seem to change their nature the further down you go. We’ve been calling the transition zone the jovicline, and its discovery has only been made possible by Juno’s microwave instrument.

This jovicline is nearly coincident with an atmospheric layer that is stable and created by condensing water.

Dr. Scott Bolton, Principal Investigator for the Juno mission, said: These amazing results provide our first glimpse of how Jupiter’s famous zones and belts evolve with depth, revealing the power of investigating the giant planet’s atmosphere in three dimensions.

More Information

University of Leicester press release

“Jupiter’s Temperate Belt/Zone Contrasts Revealed at Depth by Juno Microwave Observations,” L. N. Fletcher et al., 2021 October 28, JGR Planets