Category: saturn

Rhea (moon of Saturn)

Rhea is the second-largest moon of Saturn and the ninth-largest moon in the Solar System. It was discovered in 1672 by Giovanni Domenico Cassini.

Rhea is named after the Titan Rhea of Greek mythology, the “mother of the gods”. It is also designated Saturn V (being the fifth major moon going outward from the planet, after Mimas, Enceladus, Tethys, and Dione).

Rhea is an ice-cold body of weak density, indicating that the moon consists of a rocky nucleus counting only for a third of the mass of Rhea, the rest being mainly some ice-cold water. The temperature on the surface of Rhea is of-174°C in the sun, and of-200°C in-220°C in the shadow. In synchronous rotation around Saturn, Rhea always presents the same hemisphere to Saturn.

Rhea has a rather typical heavily cratered surface, with the exceptions of a few large Dione-type chasmata or fractures on the trailing hemisphere (the side facing away from the direction of motion along Rhea’s orbit) and a very faint “line” of material at Rhea’s equator that may have been deposited by material deorbiting from its rings. Rhea has two very large impact basins on its anti-Cronian hemisphere (facing away from Saturn), which are about 400 and 500 km across. The more northerly and less degraded of the two, called Tirawa, is roughly comparable to the basin Odysseus on Tethys.

Possible ring system

On March 6, 2008, NASA announced that Rhea may have a tenuous ring system. This would mark the first discovery of rings around a moon. The rings’ existence was inferred by observed changes in the flow of electrons trapped by Saturn’s magnetic field as Cassini passed by Rhea. Dust and debris could extend out to Rhea’s Hill sphere, but were thought to be denser nearer the moon, with three narrow rings of higher density. read more

images; NASA/JPL, Kevin GillLunar & Planetary Institute, 2id7 & titanio44

Gordan Ugarkovic

Saturn in Near UV and Blue

image credit;

Judy Schmidt

Saturn and Moon

Image credit: Tunc Tezel (TWAN)

Dione – False Color – April 24 2007

Credit: NASA/JPL-Caltech/SSI/CICLOPS/Kevin M. Gill

On March 31, 2005, just minutes after the Cassini spacecraft’s closest approach to Titan during the Titan (T-4) Flyby, Cassini viewed Saturn peeking through Titan’s thick atmosphere.

Saturn’s rings are seen here casting dark, dramatic shadows across the planet’s northern disk (upper left).

Credit: NASA / JPL / SSI / Ian Regan / Val Klavans

On March 31, 2005, just minutes after the Cassini spacecraft’s closest approach to Titan during the Titan (T-4) Flyby, Cassini viewed Saturn peeking through Titan’s thick atmosphere.

Saturn’s rings are seen here casting dark, dramatic shadows across the planet’s northern disk (upper left).

Credit: NASA / JPL / SSI / Ian Regan / Val Klavans

Moon and Saturn

Credit: Jens Hackmann

Vortex at Saturn’s North Pole

Credit: NASA/JPL-Caltech/Space Science Institute

Saturn’s atmosphere exhibits a banded pattern similar to Jupiter’s, but Saturn’s bands are much fainter and are much wider near the equator. The nomenclature used to describe these bands is the same as on Jupiter. Saturn’s finer cloud patterns were not observed until the flybys of the Voyager spacecraft during the 1980s. Since then, Earth-based telescopy has improved to the point where regular observations can be made. The composition of the clouds varies with depth and increasing pressure.

The winds on Saturn are the second fastest among the Solar System’s planets, after Neptune’s. Voyager data indicate peak easterly winds of 500 m/s (1,800 km/h).

Thermography has shown that Saturn’s south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System. Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, suspected to be the warmest spot on Saturn.

Credit: NASA/JPL-Caltech/Space Science Institute and Kevin M. Gill

Saturn and Titan

Credit: NASA/JPL-Caltech/Space Science Institute