You’ve heard of Jupiter’s Great Red Spot (seen in dark blue in the ultraviolet image above). But how about the ephemeral, Earth-sized dark ovals by Jupiter’s poles? They might be an indication of processes in Jupiter’s magnetic field. Scientists said last week that these dark ovals are likely whipped up by a disturbance high in Jupiter’s ionosphere. They described a magnetic tornado stirring up the haze.
The dark ovals on Jupiter aren’t constant features … is anything in nature constant? The scientists analyzed yearly images that the Hubble Space Telescope captured between the years 2015 and 2022. In these ultraviolet-light images, a dark oval appears 75% of the time at Jupiter’s south pole. And, in eight images from Jupiter’s north pole, the scientists counted one dark oval.
The scientists said the Earth-sized ovals typically appear in Jupiter’s stratospheric layers, under the region where Jupiter’s bright auroras reside.
Jupiter has a strong magnetic field. The scientists said these dark ovals might indicate a process creating disturbances not just high in Jupiter’s atmosphere, but reaching deep into the atmosphere.
The peer-reviewed journal Nature Astronomy published the result of the scientists’ study on November 26, 2024.
Hubble first spotted these dark ovals in Jupiter’s atmosphere in the late 1990s. Hubble’s Outer Planet Atmospheres Legacy (OPAL) project takes yearly images of the gas giant planets in order to track their changing atmospheres. But the dark ovals on Jupiter haven’t drawn a lot of attention from scientists. Co-author Troy Tsubota of UC Berkeley said:
In the first two months, we realized these OPAL images were like a gold mine, in some sense, and I very quickly was able to construct this analysis pipeline and send all the images through to see what we get. That’s when we realized we could actually do some good science and real data analysis and start talking with collaborators about why these show up.
Tsubota and co-author Michael Wong reached out to planetary atmospheric scientists to understand what might cause these dark ovals. Co-author Tom Stallard at Northumbria University in Newcastle-upon-Tyne in the U.K. suggested the ovals might be stirred up by magnetic tornadoes. Stallard had previously detected spinning in the Jovian ionosphere, which can create friction that leads to haze. Another source of atmospheric friction would be from the volcanic moon Io, which expels hot plasma that Jupiter’s magnetic field lines sweep up.
So the ovals likely come from the spinning atmosphere above in the way that a tornado on Earth reaches down to stir up the dusty landscape. Planetary atmospheric scientist and co-author Xi Zhang at UC Santa Cruz said:
The haze in the dark ovals is 50 times thicker than the typical concentration, which suggests it likely forms due to swirling vortex dynamics rather than chemical reactions triggered by high-energy particles from the upper atmosphere. Our observations showed that the timing and location of these energetic particles do not correlate with the appearance of the dark ovals.
Wong said:
Studying connections between different atmospheric layers is very important for all planets, whether it’s an exoplanet, Jupiter or Earth. We see evidence for a process connecting everything in the entire Jupiter system, from the interior dynamo to the satellites and their plasma tori to the ionosphere to the stratospheric hazes. Finding these examples helps us to understand the planet as a whole.
Bottom line: Scientists have analyzed dark ovals that appear near the poles on Jupiter. They believe magnetic tornadoes in higher atmospheric layers are stirring up the haze.
Source: UV-dark polar ovals on Jupiter as tracers of magnetosphere–atmosphere connections
Read more: Jupiter’s stormy weather on display in new Hubble images
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