Astronomers from the University of California, Berkeley have identified dark ultraviolet ovals at Jupiter's poles, observed through the Hubble Space Telescope. These ovals, which appear alongside the Great Red Spot, are zones of concentrated stratospheric haze, likely influenced by vortices in the planet's ionosphere.
These dark features, comparable in size to Earth, are only visible in ultraviolet wavelengths and are often located beneath the bright auroral regions at each pole. The ovals absorb more ultraviolet light than their surroundings, making them appear dark in Hubble's images. Between 2015 and 2022, dark ovals were detected in 75% of the observations of the southern pole, while only one was recorded at the northern pole.
The discovery suggests unusual atmospheric processes linked to Jupiter's strong magnetic field, extending deep into the atmosphere. The research, published in Nature Astronomy, indicates that these ovals may form over a month and dissipate within weeks.
Initial observations of these features date back to the late 1990s, but their significance was not fully recognized until recent systematic studies. The team, led by undergraduate Troy Tsubota, found eight southern dark ultraviolet ovals between 1994 and 2022, compared to two northern ones in 25 global maps of Jupiter.
Collaboration with planetary atmosphere experts provided insights into the dynamics causing these dark features. The prevailing theory suggests that the ovals result from a vortex in the ionosphere, which mixes the stratospheric haze below. The haze in these ovals is 50 times denser than typical concentrations, indicating that the dynamics of the vortices play a crucial role in their formation.
This research enhances understanding of atmospheric dynamics across the solar system's giant planets, shedding light on the connections between different atmospheric layers.