Andrew McCarthy
Jupiter’s Great Red Spot has been a constant feature of the planet for centuries, but recently, astronomers at the University of California, Berkeley discovered equally large spots at the planet’s north and south poles that appear and disappear seemingly at random.
The Earth-sized ovals, which are only visible in ultraviolet wavelengths, are embedded in stratospheric fog layers that cover the planet’s poles.
According to , they are almost always located below the bright auroral zones at each pole, similar to Earth’s northern and southern lights.
(dr) Troy Tsubota e Michael Wong
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These spots absorb more ultraviolet rays than the surrounding area, making them appear dark in images from NASA’s Hubble Space Telescope.
In annual images of the planet taken by Hubble between 2015 and 2022, a dark ultraviolet oval spot appears 75% of the time at the south pole, while dark ovals appear in just one of eight images taken from the north pole.
According to experts, dark ultraviolet ovals are a sign that things are happening. unusual processes in the very strong magnetic field of Jupiter, which propagate towards the poles and deep into the atmosphere.
Ultraviolet ovals were first detected by Hubble in the late 1990s at the north and south poles and, later, at the north pole by the Cassini space probe, which passed by Jupiter in 2000.
When Troy Tsubota, a student at the University of California, conducted a systematic study of recent Hubble images, he found that they were a common feature at the South Pole: between 1994 and 2022, he said. eight southern ultraviolet dark ovals (SUDOs).
Later, he analyzed 25 Hubble maps showing Jupiter’s north pole, together with astronomer Michael Wong, and found only two ovals northern dark ultraviolet (NUDO).
Most of the Hubble images were captured as part of the project Outer Planet Atmospheres Legacy (OPAL) led by Amy Simon, planetary scientist at NASA’s Goddard Space Flight Center.
“In the first two months, we realized that these OPAL images were like a gold mine and I quickly managed to build this analysis process”, said Tsubota. “That’s when we realized we could actually do quality science and real data analysis.”
Wong and Tsubota consulted two experts on planetary atmospheres – Tom Stallard of Northumbria University and Xi Zhang of UC Santa Cruz – to determine what could cause these areas of dense haze.
Stallard suggested that the oval comes from a vortex created when the planet’s magnetic field lines experience friction in two very distant places: in the ionosphere, where astronomers detected rotating motion using ground-based telescopes, and in the layer of hot, ionized plasma around the planet, released by the volcanic moon Io.
The vortex spins faster in the ionosphere and progressively weakens as it reaches each deeper layer.
Works the same way as a tornado which lands in a dusty land: the deeper extent of the vortex stirs up the hazy atmosphere and creates the dense patches.
Based on observations, the team suspects that these ovals form over the course of about a month and dissipate in just a few weeks.
The findings were published in Nature Astronomy.
