Saturn’s spin has displayed perplexing changes when observed in the past, but it turns out that its abnormal behavior is just an illusion created by the ringed planet’s aurora. Astronomers previously noticed that Saturn appeared to exhibit a changing rotation rate, yet this made no sense — a planet can’t alter its spin out of nowhere.
A new study published in the Journal of Geophysical Research: Space Physics has finally unraveled this mystery by taking a closer look at Saturn’s aurora with NASA’s James Webb Space Telescope. Readings at the upper atmosphere revealed a continuous cycle powered by wind and heat; the auroral signal created by this process has made it look as if Saturn spins at different speeds depending on how the planet is observed.
Read More: A Rogue Planet the Size of Saturn Detected 10,000 Light-Years From Earth
Saturn’s Mysterious Spin
Measuring the length of a day on Saturn is quite the challenge for astronomers, something they realized when NASA’s Cassini spacecraft observed the planet in 2004.
According to the W.M. Keck Observatory, Cassini measured radio emission pulses from Saturn’s atmosphere in an attempt to measure the bulk rotation of the planet, which should have determined the length of its day. But astronomers were left with a puzzle instead of answers: The rotation rate appeared to have changed since the last visit to Saturn by the Voyager 2 spacecraft in 1981.
Astronomers knew that Saturn’s rotation rate couldn’t have experienced significant changes without some other influence. This issue wouldn’t be deciphered until nearly two decades later, when a 2021 study in Geophysical Research Letters found that winds in the planet’s upper atmosphere were producing electrical currents responsible for the presumed changes in rotation rate.
The new study has now taken things a step further, figuring out where these winds are coming from.
“For decades, we knew something strange was happening with Saturn’s apparent rotation rate, but we could not explain it. We then showed it was being driven by atmospheric winds, but we still did not know why those winds existed. These new observations, made possible by JWST, finally give us the evidence we needed to close that loop,” said study author Tom Stallard, a planetary astronomer at Northumbria University, in a statement.
An Auroral Cycle
The new study observed Saturn’s northern auroral region — akin to Earth’s northern lights — to collect data that proved 10 times more accurate than previous measurements. Focusing on trihydrogen cation, a molecule in the planet’s upper atmosphere that acts as a natural thermometer, the researchers created detailed maps of temperature and particle density across the auroral region.
Based on heating and cooling patterns, they found that the aurora heats the atmosphere in a specific location and produces winds; these winds then generate electrical currents that form the basis of the aurora, which then heat the atmosphere again. The whole process is a self-sustaining feedback loop that continually sustains auroras.
Energy From the Magnetosphere
The new study also indicates that auroral currents generated in Saturn’s atmosphere directly influence its magnetosphere, the region surrounding the planet that is affected by its magnetic field.
“This result changes how we think about planetary atmospheres more generally,” said Stallard. “If a planet’s atmospheric conditions can drive currents out into the surrounding space environment, then understanding what is happening in the stratospheres of other worlds may reveal interactions we have not yet even imagined.”
Other planets’ magnetospheres similarly play a role in creating auroras; on Earth, for example, auroras form when charged particles from the solar wind interact with the planet’s magnetic field. Jupiter’s auroras stem from magnetic field interactions with both solar wind and particles that are ejected from volcanoes on Io, one of the planet’s orbiting moons, according to the ESA.
Ultimately, though, Saturn is a special case; it’s the only planet observed to date that generates its aurora with the help of atmospheric winds, causing the unusual appearance of its spin.
Read More: Saturn’s Rings Formed Long After the Planet
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Source: Read Full Article
