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The Hubble Space Telescope has captured images of a mysterious show unfolding on Saturn’s rings – eerie, fleeting “spokes” that appear to move along the planet’s rings. And scientists still cannot explain why the phenomena occur.
The return of the spokes is one of the earliest signs that Saturn is entering a new season, as it approaches its northern hemisphere’s autumnal equinox for the first time in about 15 years, expected to occur on May 6, 2025.
Scientists have long known about the confusing spokes, which look like apparitions gliding along Saturn’s rings and are seen around the planet at the equinox. The first evidence was captured by NASA’s Voyager mission in the 1980s.
Exactly what caused the events still eludes scientists. But this time, NASA researchers hope to finally solve the mystery.
Hubble will continue to monitor the spokes, which are expected to gain prominence in the run-up to the 2025 equinox, and provide more data on the fascinating events.
“The suspected culprit for the spokes is the planet’s variable magnetic field,” according to a NASA press release. “Planetary magnetic fields interact with the solar wind and create an electrically charged environment.
“When these charged particles hit the atmosphere on Earth, it’s visible in the northern hemisphere as the Aurora Borealis, or Northern Lights.”
Essentially, scientists hypothesize that this activity allows tiny particles to become charged, causing them to momentarily rise higher than the surrounding material and create what appears to be a bulge.
Scientists hope the forthcoming Hubble data will prove or disprove this theory once and for all, building on observations collected by Voyager and Cassini, the dedicated Saturn probe that observed the spoke phenomenon during its last appearance in the late 2000s.
“Despite years of excellent observations by the Cassini mission, the exact start and duration of the spoke season is still unpredictable, much like the prediction of the first storm of hurricane season,” said Amy Simon, ret Senior planetary scientist at NASA who directs the Hubble Outer Planet Atmospheres Legacy program, in a statement.
According to NASA, the spokes are only visible around Saturn’s equinox, when the planet’s rings are tilted towards the Sun. The marks may appear as bright points of light or black spots depending on the viewing angle of the viewing instrument.
It is possible that other ringed planets are experiencing similar events, although so far they have only been observed around Saturn’s densely packed and very prominent rings.
“It’s a fascinating magic trick of nature that we only see on Saturn — at least for now,” said Simon.
Caption: Seven Hubble Space Telescope images, each taken about four minutes apart, have been stitched together to show “spoke” features rotating around Saturn.
