Abstract
Aerosols in Jupiter’s stratosphere form intriguing polar hoods, which have been investigated by ultraviolet cameras on Cassini and the Hubble Space Telescope. Transient, concentrated dark ovals of unknown origin have been noted within both the northern and southern polar hoods. However, a systematic comparative study of their properties, which could elucidate the physical processes active at the poles, has not yet been performed due to infrequent observations. Using 26 global maps of Jupiter taken by Hubble between 1994 and 2022, we detected transient ultraviolet-dark ovals with a 48% to 53% frequency of occurrence in the south. We found the southern dark oval to be 4 to 6 times more common than its northern counterpart. The southern feature is an anticyclonic vortex and remains within the auroral oval during most of its lifetime. The oval’s darkness is consistent with a 20 to 50 times increase in haze abundance or an overall upward shift in the stratospheric haze distribution. The anticyclonic vorticity of the dark oval is enhanced relative to its surroundings, which represents a deep extension of the higher-altitude vortices previously reported in the thermosphere and upper stratosphere. The haze enhancement is probably driven by magnetospheric momentum exchange, with enhanced aerosols producing the localized heating detected in previous infrared retrievals.
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Data availability
Raw and calibrated HST images are available by searching the MAST archive, https://mast.stsci.edu. Polar mosaics and other high-level science products are available from https://doi.org/10.17909/dkep-y451 (ref. 39).
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Acknowledgements
This research is based on observations made with the NASA/ESA HST, obtained from the Data Archive at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with programme numbers listed in Table 1. Support for T.K.T., M.H.W. and A.A.S. was provided by NASA through a grant from STScI for programme GO-13937 (Outer Planet Atmospheres Legacy). X.Z. is supported by the National Science Foundation (grant no. AST2307463) and NASA (Exoplanet Research grant no. 80NSSC22K0236). We are grateful to S. Levin for inviting M.H.W. to give the JPL Astrophysics Colloquium in 2022, which led to the discovery of the first SUDO in WFC3 data.
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T.K.T. led the project, processed the HST dataset, constructed the oval morphology analysis pipeline, created the figures, made the data archive and wrote the paper. M.H.W. conceived the project, calibrated the HST data, measured the SUDO vorticity and wrote the discussion. T.S. provided the magnetospheric interpretation of the polar vortices and contributed the associated manuscript text. X.Z. performed the radiative-transfer modelling and contributed the associated manuscript text. A.A.S. assisted with collecting HST/WFPC2 and Outer Planet Atmospheres Legacy data.
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Extended data
Extended Data Fig. 1 HST/WFC3 F275W north pole maps.
North polar maps show one NUDO present in fifteen WFC3 observation dates. Refer to Fig. 2 and Methods for detection criteria.
Extended Data Fig. 2 HST/WFPC2 F255W south pole maps.
South polar maps show SUDOs present in 3 of 10 WFPC2 observation dates. Refer to Fig. 2 and Methods for detection criteria.
Extended Data Fig. 3 HST/WFPC2 F255W north pole maps.
North polar maps show one NUDO present in ten WFPC2 observation dates. Refer to Fig. 2 and Methods for detection criteria.
Extended Data Fig. 4 Additional ellipse fits.
Additional ellipse fits for the 1997.71 NUDO, 2015.15 SUDO, and 2017.25 SUDO.
Extended Data Fig. 5 SUDO in different wavelengths.
South polar maps of the 2017.09 observations with the F225W, F275W, and FQ889N filters. The F225W and F275W UV-band filters show very similar results. The FQ889N methane-band filter does not show a SUDO detection despite its detection in the UV.
Extended Data Fig. 6 Radiative transfer model details.
Radiative transfer model for 81°S. Subfigure (a) compares the observed I/F values (horizontal lines, error bars shaded) to the model I/F values (scatter points) at different haze multipliers relative to baseline. The shaded error is the same as that for 81° latitude in Fig. 4b. Blue and red correspond to 68° and 11° CML offsets, respectively. The grayed out lines denote the observed background, while the bright lines denote the observed SUDO I/F. Subfigure (b) shows the optical thickness over pressure for the 70°S background (gray), 75°S background (black), and the × 50 haze model at 75°S (blue).
Extended Data Fig. 7 SUDO rotation measurement.
To estimate the rotation of the SUDO, we manually identified seven low-contrast tie points in the 2017.09 data. Using the area of 1.6 × 108 km2 (Table 1), we estimate a characteristic radius R of 7100 km, which gives a characteristic tangential wind speed of 21 m/s for a period of 590 hours. The vorticity is then u/R = − 3 × 10−6 s−1 (negative for anticyclonic rotation). Top row: polar maps at 275 nm, separated by 9.9 hours. Bottom row: Colored circles indicate manual tracking tie points, with angular displacements relative to the SUDO center (white square; see Extended Data Table 1) labeled in matching color. The angular displacements were measured by comparing the dashed and solid white line segments in the lower right panel. An animated version of this figure is available as a Supplementary Video.
Supplementary information
Supplementary Video
Estimating the rotation of a SUDO by manually tracking points in two different frames. See Extended Data Fig. 7 for a more detailed description.
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Tsubota, T.K., Wong, M.H., Stallard, T. et al. UV-dark polar ovals on Jupiter as tracers of magnetosphere–atmosphere connections. Nat Astron 9, 221–229 (2025). https://doi.org/10.1038/s41550-024-02419-0
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DOI: https://doi.org/10.1038/s41550-024-02419-0
