Mooning amongst the Gas Giants

Saturn's big four

Titan is Saturn's largest moon and is the second largest moon in the Solar System (Jupiter's moon Ganymede is the largest).  It is the only natural satellite known to have a dense atmosphere.  The atmosphere is primarily composed of nitrogen.  Titan has its own weather systems in which methane and ethane clouds feature.  Titan's methane cycle is analogous to Earth's water cycle, albeit operational at much lower temperatures. In 2004, the Cassini probe Huygens, discovered Earth-like surface features including: dunes, rivers, lakes and seas. Titan has an approximate diameter of 5152 kms and orbits Saturn once every 16 days (384 hours).

The Huygens shoreline and specular reflection of infra-red light
off a methane or ethane sea at Titan's Pole

Rhea is Saturn's second largest moon after Titan.  It has a diameter of approximately 1520 kms and orbits Saturn once every 108 hours.  Rhea has a low mean density as it is composed of 75% water ice and only 25%  rock.

Dione has a diameter of approximately 1120 kms and orbits Saturn once every 66 hours.  Much like Rhea, it is predominantly water ice but has a much higher mean density.  The higher density is because Dione has a dense core whereas Rhea probably does not.

Tethys has a diameter of approximately 1060 kms and orbits Saturn once every 45 hours.  It has a very low mean density, lower than Rhea, and is composed of predominantly water ice.  Tethys has a high albedo, it reflects a large proportion of the light incident upon it.

When I capture light from Saturn and its moons it is reflected photons of sunlight that I collect and use to create my photographs.  Such photons have taken a round trip lasting roughly 2 hours.  Light travels at approximately 300 million kilometers per second!

Titan, Rhea, Dione, Tethys and three other Saturnian moons were named by John Herschel, the son of William Herschel co-discoverer of Uranus.  In Greek Mythology the Titans were the descendants of the Earth God, Gaia, and the God of the Sky, Uranus.  The Titans, although enormous and strong (hence the common usage of the word titanic), were eventually overthrown and replaced by the 'Olympian Pantheon' of deities headed by Zeus.

Credits: Wikipedia,NASA/JPL- Caltech for information and base images.