Details

Autor(en) / Beteiligte

• Adriani, A.
• Mura, A.
• Orton, G.
• Hansen, C.
• Altieri, F.
• Moriconi, M. L.
• Rogers, J.
• Eichstädt, G.
• Momary, T.
• Ingersoll, A. P.
• Filacchione, G.
• Sindoni, G.
• Tabataba-Vakili, F.
• Dinelli, B. M.
• Fabiano, F.
• Bolton, S. J.
• Connerney, J. E. P.
• Atreya, S. K.
• Lunine, J. I.
• Tosi, F.
• Migliorini, A.
• Grassi, D.
• Piccioni, G.
• Noschese, R.
• Cicchetti, A.
• Plainaki, C.
• Olivieri, A.
• O’Neill, M. E.
• Turrini, D.
• Stefani, S.
• Sordini, R.
• Amoroso, M.

Titel

Clusters of cyclones encircling Jupiter’s poles

Ist Teil von

• Nature (London), 2018-03, Vol.555 (7695), p.216-219

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2018

Beschreibungen/Notizen

• Visible and infrared images obtained from above each pole of Jupiter by the Juno spacecraft reveal polygonal patterns of large cyclones; it is unknown how these cyclones evolved, or how they persist without merging. Polygonal cyclones around Jupiter's poles Jupiter's colourful low-latitude weather bands turn into cyclones at high latitudes, but the polar region is not visible from Earth and was poorly characterized by previous spacecraft. Alberto Adriani and colleagues report visible and infrared observations of Jupiter's polar regions made by the Juno spacecraft, which is in a highly elliptical polar orbit. They find that the cyclones create persistent polygonal patterns. There are eight circumpolar cyclones rotating around a single cyclone in the north, while the South Polar Cyclone is circled by five such features. The authors do not know how these cyclones evolved to their current state or how they persist without merging. The familiar axisymmetric zones and belts that characterize Jupiter’s weather system at lower latitudes give way to pervasive cyclonic activity at higher latitudes 1 . Two-dimensional turbulence in combination with the Coriolis β-effect (that is, the large meridionally varying Coriolis force on the giant planets of the Solar System) produces alternating zonal flows 2 . The zonal flows weaken with rising latitude so that a transition between equatorial jets and polar turbulence on Jupiter can occur 3 , 4 . Simulations with shallow-water models of giant planets support this transition by producing both alternating flows near the equator and circumpolar cyclones near the poles 5 , 6 , 7 , 8 , 9 . Jovian polar regions are not visible from Earth owing to Jupiter’s low axial tilt, and were poorly characterized by previous missions because the trajectories of these missions did not venture far from Jupiter’s equatorial plane. Here we report that visible and infrared images obtained from above each pole by the Juno spacecraft during its first five orbits reveal persistent polygonal patterns of large cyclones. In the north, eight circumpolar cyclones are observed about a single polar cyclone; in the south, one polar cyclone is encircled by five circumpolar cyclones. Cyclonic circulation is established via time-lapse imagery obtained over intervals ranging from 20 minutes to 4 hours. Although migration of cyclones towards the pole might be expected as a consequence of the Coriolis β-effect, by which cyclonic vortices naturally drift towards the rotational pole, the configuration of the cyclones is without precedent on other planets (including Saturn’s polar hexagonal features). The manner in which the cyclones persist without merging and the process by which they evolve to their current configuration are unknown.