Jupiter’s zonal winds and their variability studied with small-size telescopes

International audienc

Jupiter's third largest and longest-lived oval: Color changes and dynamics

The transition region between the North Equatorial Band (NEBn) and North Tropical Zone (NTrZ) in Jupiter is home to convective storms, systems of cyclones and anticyclones and atmospheric waves. Zonal winds are weak but have a strong latitudinal shear allowing the formation of cyclones (typically dark) and anticyclones (typically white) that remain close in latitude. A large anticyclone formed in the year 2006 at planetographic latitude 19°N and persists since then after a complex dynamic history, being possibly the third longest-lived oval in the planet after Jupiter's Great Red Spot and oval BA. This anticyclone has experienced close interactions with other ovals, merging with another oval in February 2013; it has also experienced color changes, from white to red (September 2013) and back to white with an external red ring (2015–2016). The oval survived the effects of the closely located North Temperate Belt Disturbance, which occurred in October 2016 and fully covered the oval, rendering it unobservable for a short time. When it became visible again at its expected longitude from its previous longitudinal track, it reappeared as a white large oval keeping this color and the same morphology since 2017 at least until the onset of the new convective disturbance in Jupiter's North Temperate Belt in August 2020. Here we describe the historic evolution of the properties of this oval. We use JunoCam and Hubble Space Telescope (HST) images to measure its size obtaining a mean value of (10,500 ± 1000) x (5,800 ± 600) km2 and its internal rotation finding a value of -(2 ± 1)·10−5 s−1 for its mean relative vorticity. We also used HST and PlanetCam-UPV/EHU multi-wavelength observations to characterize its color changes and Junocam images to unveil its detailed structure. The color and the altitude-opacity indices show that the oval is higher and has redder clouds than its environment but has lower cloud tops than other large ovals like the GRS, and it is less red than the GRS and oval BA. We show that in spite of the dramatic environmental changes suffered by the oval during all these years, its main characteristics are stable in time and therefore must be related with the atmospheric dynamics below the observable cloud decks.This work has been supported by the Spanish projects AYA2015-65041-P, PID2019-109467GB-100 (MINECO/FEDER, UE) and Grupos Gobierno Vasco IT1366-19. P. Iñurrigarro acknowledges a PhD scholarship from Gobierno Vasco. I. Ordonez-Etxeberria's was supported by contract from Europlanet 2024 RI. Europlanet 2024 RI has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 871149. This work used data acquired from the NASA/ESA HST Space Telescope, associated with OPAL program (PI: Simon, GO13937) and programs GO/DD 13067 (PI: Glenn Schneider), GO 14661 (PI: Michael Wong) and GO 14839 (PI: Imke de Pater), and archived by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26,555. HST/OPAL maps are available at http://dx.doi.org/10.17909/T9G593. Junocam images are available at https://www.missionjuno.swri.edu/junocam/ and at the PDS Cartography and Imaging Sciences Node at: https://pds-imaging.jpl.nasa.gov/volumes/juno.html. This research has made use of the USGS Integrated Software for Imagers and Spectrometers (ISIS). PlanetCam observations were collected at the Centro Astronómico Hispánico en Andalucía (CAHA), operated jointly by the Instituto de Astrofisica de Andalucia (CSIC) and the Andalusian Universities (Junta de Andalucía) and are available on request from the instrument PI Agustín Sánchez-Lavega. Amateur images are available at the PVOL website https://pvol2.ehu.eus. LAIA and PLIA can be downloaded from: http://www.ajax.ehu.es/Software/laia.html and http://www.ajax.ehu.es/PLIA respectively. The software PICV is available at zenodo with doi: https://doi.org/10.5281/zenodo.4312674

Deep winds beneath Saturn's upper clouds from a seasonal long-lived planetary-scale storm.

Convective storms occur regularly in Saturn's atmosphere. Huge storms known as Great White Spots, which are ten times larger than the regular storms, are rarer and occur about once per Saturnian year (29.5 Earth years). Current models propose that the outbreak of a Great White Spot is due to moist convection induced by water. However, the generation of the global disturbance and its effect on Saturn's permanent winds have hitherto been unconstrained by data, because there was insufficient spatial resolution and temporal sampling to infer the dynamics of Saturn's weather layer (the layer in the troposphere where the cloud forms). Theoretically, it has been suggested that this phenomenon is seasonally controlled. Here we report observations of a storm at northern latitudes in the peak of a weak westward jet during the beginning of northern springtime, in accord with the seasonal cycle but earlier than expected. The storm head moved faster than the jet, was active during the two-month observation period, and triggered a planetary-scale disturbance that circled Saturn but did not significantly alter the ambient zonal winds. Numerical simulations of the phenomenon show that, as on Jupiter, Saturn's winds extend without decay deep down into the weather layer, at least to the water-cloud base at pressures of 10-12 bar, which is much deeper than solar radiation penetrates