JUPITER

Pole position for Juno

Adriani, A. et al. Nature 555, 216–219 (2018); Iess, L. et al. Nature 555, 220–222 (2018); Kaspi, Y. et al. Nature 555, 223–226 (2018); Guillot, T. et al. Nature 555, 227–230 (2018)

Jupiter’s poles are a clash of atmospheric and magnetospheric phenomena that has not been studied up close. NASA’s Juno spacecraft, with its polar orbit that takes in both poles every 53 days, is redressing the imbalance. Early images taken by JunoCam revealed spectacular rings of cyclones at the poles. Alberto Adriani et al. now report high-resolution visible and infrared images that show stable polygonal arrangements of cyclones swirling about the two circumpolar cyclones. Around the Northern Polar Cyclone (pictured left, in the infrared), the cyclones form an octagonal pattern, with four alternating cyclones (forming a square) centred at one point and the other four centred about another. To the south, only five, albeit larger, cyclones surround the Southern Polar Cyclone (right), which uniquely has an oblong eye-shaped centre. The relative stability of these giant vortices among the surrounding chaos and turbulence is a puzzle.

Credit: Macmillan Publishers Ltd

Jupiter’s striking planetary-scale bands of atmospheric clouds obscure all the action happening in the interior. To probe the deeper flows, Luciano Iess et al. map the global gravity harmonics through Doppler tracking of the spacecraft, itself acting as a test particle in Jupiter’s gravity field (the second end-mass being Earth). The measured north–south asymmetry arises from atmospheric and interior flows, showing up as odd gravity harmonics. Yohai Kaspi’s team analysed the odd harmonics to estimate the depth of the atmospheric jet streams as extending down to 3,000 km beneath the cloud level. The even harmonics help Tristan Guillot and collaborators sound out Jupiter’s deep internal rotational dynamics. Their results are consistent with the differential rotation of the atmosphere reaching a depth of 2,000–3,500 km, below which the unseen interior rotates as a rigid body. These constraints will improve models of Jupiter and other giant planets.

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Correspondence to May Chiao.

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Chiao, M. Pole position for Juno. Nat Astron 2, 279 (2018). https://doi.org/10.1038/s41550-018-0444-x

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