Jupiter’s Great Red Spot has been a subject of intrigue for centuries. However, astronomers from the University of California, Berkeley, have brought attention to similar, Earth-sized spots present at the planet’s poles. These intriguing features, which can only be seen in ultraviolet wavelengths, appear and disappear randomly.
These dark ovular formations are nestled within layers of haze that cover Jupiter’s poles. They are typically located just beneath the bright auroral zones at each pole, comparable to Earth’s northern and southern lights. The spots absorb more ultraviolet light than their surroundings, making them appear dark in images taken by NASA’s Hubble Space Telescope.
The researchers found that a dark ultraviolet oval was visible 75% of the time at the south pole in yearly images of Jupiter taken by Hubble from 2015 to 2022. However, dark ovals were spotted in only one of eight images of the north pole. These observations suggest unique processes at play within Jupiter’s magnetic field that extend deep into the atmosphere and beyond the magnetic processes that create Earth’s auroras.
This discovery was published in the journal Nature Astronomy on November 26. Initial detection of these dark ultraviolet ovals dates back to the late 1990s by the Hubble, with further sightings by the Cassini spacecraft in 2000. However, they didn’t garner much attention until a systematic study of recent images revealed their consistent presence at the south pole.
The research team analysed 25 of Hubble’s global maps of Jupiter’s north pole and found only two instances of these northern ultraviolet-dark ovals. Most of these images were part of NASA’s Outer Planet Atmospheres Legacy (OPAL) project, which annually observes Jupiter, Saturn, Uranus, and Neptune to study their atmospheric dynamics and evolution.
The researchers collaborated with experts on planetary atmospheres to understand the cause of these dense haze areas. They theorized that these dark ovals are likely stirred from above by a vortex created by friction within the planet’s magnetic field lines in two distant locations. This vortex spins fastest in the ionosphere and weakens as it reaches deeper layers, stirring up the hazy atmosphere to create the dense spots observed.
The team estimates that these ovals form over approximately a month and dissipate within a few weeks. The haze within these ovals is 50 times thicker than usual, suggesting it forms due to vortex dynamics rather than chemical reactions triggered by high-energy particles from the upper atmosphere.
This research aligns with OPAL’s aim to understand how atmospheric dynamics in the giant planets of our solar system differ from Earth. The findings highlight the importance of studying the connections between different atmospheric layers on all planets, contributing to our understanding of the planetary systems as a whole. The research received support from the National Aeronautics and Space Administration.
