Giant planets

  • Article
    | Open Access

    Helium is generally considered too inert to be present in giant ice planet mantles. The authors, by first-principles calculations and crystal structure searches, find stable ammonia–helium compounds at the conditions of Uranus and Neptune’s upper mantles, with possible implications in the planet composition models.

    • Jingming Shi
    • , Wenwen Cui
    •  & Yinwei Li
  • Article
    | Open Access

    The authors analyze a system of multi-layered hazes above Saturn’s hexagonal-wave cloud tops in the visual range. Analyses suggest the formation to be caused by condensation processes, and the vertical distribution of stacked layers by the upward propagation of internal gravity waves.

    • A. Sánchez-Lavega
    • , A. García-Muñoz
    •  & J. Peralta
  • Article
    | Open Access

    Radial diffusion is the only mechanism considered to accelerate trapped electrons to relativistic energies in Saturn’s magnetic field, forming radiation belts. Here the authors show another mechanism, electron acceleration via Doppler shifted cyclotron resonant interaction with Z-mode waves, which can form radiation belts inside the orbit of Enceladus.

    • E. E. Woodfield
    • , R. B. Horne
    •  & W. S. Kurth
  • Article
    | Open Access

    Radiant energy budgets and internal heat play a key role in the evolution of planets. Here, the authors analyze data from the Cassini mission to show that Jupiter’s radiant energy and internal heat budgets are significantly larger than previous estimates.

    • Liming Li
    • , X. Jiang
    •  & R. W. Schmude Jr.
  • Article
    | Open Access

    The Cassini spacecraft has provided an unprecedented characterisation of seasonal changes on Saturn. Here the authors describe the development of a warm polar vortex in Saturn’s northern summer, and show that the hexagon extends hundreds of kilometres from the troposphere into the stratosphere.

    • L. N. Fletcher
    • , G. S. Orton
    •  & S. B. Calcutt
  • Article
    | Open Access

    Observations of Jupiter’s magnetosphere provide opportunities to understand how magnetic fields interact with particles. Here, the authors report that the chorus wave power is increased in the vicinity of Europa and Ganymede. The generated waves are able to accelerate particles to very high energy.

    • Y. Y. Shprits
    • , J. D. Menietti
    •  & D. A. Gurnett
  • Article
    | Open Access

    The origin, variability, and structure of Saturn’s intense and broad eastward equatorial jet at upper cloud level are complex and unexplained. Here, based on observations of a large, bright equatorial disturbance in 2015, the authors characterise the vertical structure of the jet and its long-term variability.

    • A. Sánchez-Lavega
    • , E. García-Melendo
    •  & T. Barry