Rhea

Rhea is one of the seven regular moons of Saturn. This moon has a small atmosphere, known as an exosphere, that surrounds the surface. Learn all about Rhea here!

Formation

Rhea is believed to have formed because of the processes that shaped the early Saturnian system. Current theories suggest that Rhea, like other moons and planets, emerged from the protoplanetary disk of gas and dust encircling the young Sun. Particles within this disk collided and aggregated under the influence of gravity, forming progressively larger objects. Rhea likely formed within Saturn's circumplanetary disk, closer to the planet. Its composition, predominantly comprising water ice and rocky material, reflects the conditions specific to its region within the disk. Following its formation, Rhea experienced internal differentiation, with denser materials settling into its core and lighter materials forming its icy mantle.

Surface

Rhea presents a diverse and intriguing surface marked by a mixture of geological features. Its most distinguishing aspect is the prominent "wispy terrain," consisting of long, bright fractures that crisscross its surface. These fractures, which are believed to result from tectonic forces, provide insights into Rhea's internal dynamics and geological history. Additionally, Rhea's surface is dotted with impact craters of varying sizes, ranging from small pits to larger basins, offering clues about its collisional history. Notably, the moon has a rather subdued appearance in terms of topographical variations. Rhea also has an extremely tenuous exosphere, a thin layer of gases and volatile materials near its surface. This exosphere is believed to be sustained by the impact of charged particles from Saturn's magnetosphere. However, its characteristics and composition remain subjects of ongoing research.

Structure

Rhea is thought to possess an internal structure characterized by a rocky core surrounded by an icy mantle. This differentiation is inferred from its overall composition and density, indicating the presence of denser materials within. While Rhea's relatively low density compared to pure ice suggests the presence of a significant rocky component, the exact proportion and characteristics of its core and mantle are still being investigated. Its internal structure has likely been shaped by various processes including heating from radioactive decay and the gravitational interactions within the Saturnian system. Although Rhea doesn't exhibit as many signs of recent geological activity compared to some other moons, its internal structure plays a crucial role in shaping its surface features and interactions within Saturn's complex moon system.

Satellites

The Cassini spacecraft is the only spacecraft that has visited Rhea. During its mission, Cassini conducted several close flybys of Rhea, capturing detailed images, data, and insights about the moon's surface, geology, composition, and physical characteristics. These observations revealed Rhea's diverse surface features, including the "wispy terrain" fractures and impact craters. Cassini's measurements and observations contributed significantly to our understanding of Rhea's role within Saturn's moon system and the broader context of Saturn's rings and other moons.