Magnetically Driven Vortices May be Generating Earth-Size Concentrations of Hydrocarbon Haze at Jupiter's Poles
by University of California - Berkeley
While Jupiter's Great Red Spot has been a constant feature of the planet for centuries, researchers at UC Berkeley have discovered equally large spots at the planet's north and south poles that appear and disappear seemingly at random. This discovery is groundbreaking as it provides critical insights into Jupiter's atmospheric dynamics.
Overview of the Discovery
The Earth-size ovals, which are visible only at ultraviolet wavelengths, are embedded in layers of stratospheric haze that cap the planet's poles. The dark ovals, when observed, are almost always located just below the bright auroral zones at each pole, which are akin to Earth's northern and southern lights.
The spots absorb more UV radiation than the surrounding area, making them appear dark on images from NASA's Hubble Space Telescope. In yearly images of the planet taken by Hubble between 2015 and 2022, a dark UV oval appears 75% of the time at the south pole, while dark ovals appear in only one of eight images taken of the north pole.
This unique phenomenon hints at unusual processes taking place in Jupiter's strong magnetic field that propagate down to the poles and deep into the atmosphere, far deeper than the magnetic processes that produce the auroras on Earth.
Methodology
Dark UV ovals were first detected by Hubble in the late 1990s at the north and south poles. Subsequent detections were made by the Cassini spacecraft during its flyby of Jupiter in 2000; however, these observations received little attention at that time.
When UC Berkeley undergraduate Troy Tsubota conducted a systematic study of recent images obtained by Hubble, he discovered that these dark ovals at the south pole were more common than previously reported—counting up to eight southern UV-dark ovals (SUDO) between 1994 and 2022.
Analysis of Hubble's Data
In all 25 of Hubble's global maps that show Jupiter's north pole, Tsubota and senior author Michael Wong, an associate research astronomer at UC Berkeley's Space Sciences Laboratory, noted only two northern UV-dark ovals (NUDO).
Most of the Hubble images had been captured as part of the Outer Planet Atmospheres Legacy (OPAL) project directed by Amy Simon, a planetary scientist at NASA Goddard Space Flight Center and a co-author of the paper. OPAL astronomers make yearly observations of Jupiter, Saturn, Uranus, and Neptune to understand their atmospheric dynamics and evolution over time.
Theoretical Framework
As Tsubota explained, “In the first two months, we realized these OPAL images were like a gold mine, and I quickly constructed an analysis pipeline and processed all the images to see what we could find.” This exploratory approach unveiled significant features that warranted further investigation.
Wong and Tsubota collaborated with experts on planetary atmospheres—Tom Stallard at Northumbria University in Newcastle-upon-Tyne, UK, and Xi Zhang at UC Santa Cruz—to theorize the causes behind these areas of dense haze. The vortex dynamics postulated by Stallard suggest that the dark oval phenomena are likely stirred from above by a vortex.
Mechanics Behind the Vortex Formation
The vortex likely develops when the planet's magnetic field lines experience friction in two very distant locations: in the ionosphere, where the spinning motion had been previously detected using ground-based telescopes, and in the sheet of hot, ionized plasma around the planet, emitted by the volcanic moon Io.
| Observation Period | South Pole (SUDO) | North Pole (NUDO) |
|---|---|---|
| 1994-2022 | 8 detected | 2 detected |
| 2015-2022 | 75% occurrence | 12.5% occurrence |
The observed rapid spinning of the vortex in the ionosphere progressively weakens as it impacts deeper layers of Jupiter's atmosphere. The vortex stirs the hazy atmosphere similar to tornado activity on Earth.
Formative Processes and Duration
The researchers propose that the ovals may form over the course of about one month and dissipate within a few weeks. The haze observed in the dark ovals is reported to be up to 50 times thicker than the typical concentration, indicating that it likely forms through vortex dynamics rather than through chemical reactions triggered by high-energy particles from the upper atmosphere.
Connection to Atmospheric Dynamics
The findings align with the purpose of the OPAL project, which aims to discern how atmospheric dynamics in the solar system's giant planets differ from terrestrial models.
Impacts and Future Research Directions
The study presents significant implications for understanding atmospheric layers across planets, including Jupiter's unique features in the context of its magnetic field. Wong elaborated, “Studying connections between different atmospheric layers is vital for all planets, whether it's Earth or exoplanets. Finding these examples enhances our understanding of planetary systems.”
Conclusion
The discovery of magnetically driven vortices creating Earth-size hydrocarbon haze at Jupiter's poles marks a major advance in planetary science. It opens new avenues for further research into how magnetic and atmospheric forces can dramatically alter conditions on other celestial bodies.
For more information, refer to the research by Troy K. Tsubota et al, titled, UV-dark polar ovals on Jupiter as tracers of magnetosphere–atmosphere connections, published in Nature Astronomy. DOI: 10.1038/s41550-024-02419-0.