Detailed insights into the properties of Jupiter, including its gravitational field, its atmospheric flows, its interior composition and its polar cyclones, are reported in four papers published in this week’s Nature. The studies present some of the key findings of NASA’s Juno mission to the gas giant. Despite extensive studies of Jupiter’s surface, with its distinctive dark ‘bands’ and bright ‘zones’, the planet’s deep interior has remained poorly understood.
Luciano Iess and colleagues used Doppler data based upon the Juno spacecraft’s motion to study Jupiter’s gravitational field, which is known to vary from pole to pole. The authors show that this north-south asymmetry, which is unexpected for a fluid planet that is fast-rotating and oblate (squashed at the poles), results from atmospheric and interior wind flows. Two further studies assess the depths of these flows. Yohai Kaspi and colleagues analyse Jupiter’s ‘odd’ gravity moments, and show that its jet streams extend to 3,000 kilometres below cloud level. They also report that Jupiter’s turbulent atmosphere involves about 1 per cent of the planet’s total mass. From their analysis of the ‘even’ gravity moments, Tristan Guillot and co-authors find that at depths greater than 3,000 kilometres below cloud level, Jupiter’s deep interior is made up of a fluid mixture of hydrogen and helium, rotating as a solid body.
In a fourth paper, Alberto Adriani and colleagues report comprehensive visible and infrared observations made by Juno of Jupiter’s polar regions. They find that the cyclones known to exist at Jupiter’s poles create persistent polygonal patterns. At the north pole, eight circumpolar cyclones rotate around a single cyclone, whereas the south polar cyclone is circled by five such cyclones. The origins of these cyclones and how they persist without merging remain unknown, however.
Writing in an accompanying News & Views article, Jonathan Fortney concludes that if a consistent physical picture can be put together for the interior dynamics of Saturn as well as Jupiter, it would go a long way towards solidifying our understanding of the internal dynamics of this class of gas giant planets.DOI:10.1038/nature25775 | Original article
DOI:10.1038/nature25793 | Original article
DOI:10.1038/nature25776 | Original article