These Earth-size ovals at Jupiter’s north and south poles are visible only at ultraviolet (UV) wavelengths, and appear and disappear seemingly at random, according to a study led by astronomers from the University of California, Berkeley.
Jupiter’s dark UV ovals, when seen, 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 than the surrounding area, making them appear dark on images from the NASA/ESA 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.
The dark UV ovals hint 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.
Dark UV ovals were first detected by Hubble in the 1990s at the north and south poles and subsequently at the north pole by NASA’s Cassini spacecraft that flew by Jupiter in 2000, but they drew little attention.
In a new analysis of the Hubble images, University of California, Berkeley undergraduate Troy Tsubota and colleagues found the ovals were a common feature at the south pole — they counted eight southern UV-dark ovals (SUDO) between 1994 and 2022.
In all 25 of Hubble’s global maps that show Jupiter’s north pole, they found only two northern UV-dark ovals (NUDO).
Most of the Hubble images had been captured as part of the Outer Planet Atmospheres Legacy (OPAL).
“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,” Tsubota said.
“That’s when we realized we could actually do some good science and real data analysis and start…
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