Uranus's Outermost Rings Show Different Compositions Based on Telescope Data

Data from the Keck Telescope in Hawaii, the Hubble Space Telescope, and the James Webb Space Telescope, collected over nearly two decades, show differences in Uranus's outermost rings. The mu ring, the farthest out, appears blue and is composed of small ice particles.

In contrast, the nu ring appears red and includes dust along with complex organic molecules known as tholins. Researchers suggest the mu ring's particles likely originate from a small moon orbiting Uranus. This indicates the moon has an icy composition, unlike nearby rocky moons.

The process of material ejection from this moon remains unclear, though impacts from micrometeoroids may dislodge ice specks.

The situation resembles Saturn's E ring, which receives material from its moon Enceladus through water plumes. However, such plumes are unlikely on a small moon about 12 kilometers across. Instead, micrometeoroid impacts are considered a more probable mechanism for releasing ice into the ring.

The nu ring's dust suggests supply from small, undetected rocky objects. Observations also indicate the nu ring's brightness halved between 2003 and 2006, possibly due to a major collision before 2003 that temporarily increased its shine.

These differences highlight variations among bodies orbiting in similar regions around Uranus. The findings point to potential past events, such as disruptions of larger moons, that shaped the current system. Further study is needed to understand the origins and evolution of these features. The research was published in The Journal of Geophysical Research: Planets.