Scientists have confirmed that one of Uranus’s faint outer rings is made up primarily of water ice.
Professor of Physics at the University of Idaho (U of I), Matthew Hedman, contributed to the study, which was led by researchers at the University of California, Berkeley. He analyzed telescope data to help determine what the rings were made of.
An international team used observations from the W. M. Keck Observatory, the Hubble Space Telescope and the James Webb Space Telescope to construct the first complete spectrum of the planet’s outer rings, according to U of I. Those two rings are known as the μ (mu) and ν (nu) rings.
While the v ring appears to be composed of dark, rocky material, likely from debris, the μ ring is made up of very small water-ice particles, making it appear blue in the light. U of I says this is a rare trait for planetary rings.
Researchers believe that the μ ring is likely made up of material from a moon called Mab. This moon is around 10 kilometers across and appears to be made up of ice. Ice that’s knocked loose from the moon’s surface can escape the moon’s gravity but not Uranus’s, according to U of I.
“We’re finally able to see what these rings are made of,” Hedman said. “That gives us a clearer picture of how they formed and how the Uranus system has evolved over time.”
Scientists have suspected that the μ ring was made up of ice, but haven’t been able to confirm this theory until now, thanks to the James Webb Telescope, which made the discovery by detecting water in the ring.
While researchers are now aware of what the μ ring and Mab is made of, they are unaware of why it is so icy. Both seem to be icier than nearby rings and moons, most of which are made up of dark rocks, like the v ring.
Additionally, researchers note that the brightness of the ring varies over time, leading them to believe that Mab might release fresh material here and there.
“There’s something unusual happening in this part of the Uranus system that we’re still trying to understand,” Hedman said.
The research team has been granted time on the James Webb Space Telescope to observe the planet annually over the next five years, according to U of I. The hope is that the repeated observations will help track changes to better understand how the rings, planets and moons change and evolve over time.