Titan is the largest moon of the ringed gas-giant planet, Saturn, as well as the second-largest moon in our Solar System. Only Ganymede of Jupiter is larger than Titan. Here, in the frigid realm of the quartet of majestic, giant, and gaseous outer planets–Jupiter, Saturn, Uranus, and Neptune–our Sun shines with a weaker fire than it does in the inner Solar System where Earth is situated–along with the three other solid and relatively small planets: Mercury, Venus, and Mars.
Titan is a hydrocarbon-tormented world, that bears an eerie resemblance to the way our own planet was, very long ago, before life emerged and evolved here (prebiotic). Like Earth, Titan experiences frequent downpours of rain, swirling seas, and eroding organic material. However, on Titan, it is not liquid water that fills its alien seas, rivers, and lakes with lovely little raindrops. On this strange smoggy moon-world, life-sustaining liquid water is replaced by weird, lazy, large drops of methane. The surface of Titan is pelted with a “rain of terror”–on Titan, it rains gasoline. On this strange moon, atmospheric molecules composed of methane are perpetually being torn apart by sunlight, and the resulting atmospheric smog floats down to the surface, where it accumulates as organic settlements that rapidly rob the atmosphere of methane. The surface of Titan is well-coated with the material of old atmospheres that have long since vanished.
There is no obvious source of Titan’s methane, with the exception of the evaporation of methane originating from polar hydrocarbon-filled lakes. The problem is that Titan’s strange lakes contain only approximately one-third of the methane in Titan’s atmosphere. This methane will be depleted soon on geological time scales.
Titan itself is the sixth gravitationally rounded moon from Saturn, and this large moon-world is often described as being “planet-like”. Titan is twice as large as Earth’s own comparatively large Moon, as well as being 80% more massive. Indeed, Titan is larger than the planet Mercury–the innermost major planet from our Star. However, Titan is only about 40% as massive as Mercury.
Titan was discovered by the Dutch astronomer Christiaan Huygens on March 25, 1655, and it was the first moon of Saturn to be observed. It is the sixth known natural planetary satellite, after Earth’s Moon and the quartet of Galilean moons of Jupiter (Io, Europa, Ganymede, and Callisto). The four Galilean moons were discovered by the great Italian astronomer Galileo Galilei in 1610. Titan circles its ringed parent-planet at 20 Saturn radii. From Titan’s weird hydrocarbon-slashed surface, Saturn subtends an arc of 5.09 degrees, and would loom 11.4 times larger in its dense golden-orange sky than the Moon from Earth.
Titan is primarily made up of ice and rocky material, which is thought to be differentiated into a rocky core encircled by sundry layers of ice, including a crust composed of ice Ih, and a subsurface layer of ammonia-rich liquid water. Before the era of space exploration, the heavy and opaque atmosphere of Titan made it impossible of planetary scientists to study its mysterious surface–until the Cassin-Huygens mission. This joint NASA/European Space Agency/Italian Space Agency mission to the Saturn system, finally revealed the strange moon’s face that had been well-hidden behind its smoggy orange mask since its discovery in 1655. Cassini-Huygens provided precious new information, including the discovery of the liquid hydrocarbon lakes pooling in Titan’s polar regions. The geologically youthful surface is mostly smooth, sporting relatively few impact craters. Smooth surfaces are young, while heavily cratered surfaces are more ancient. This is because young surfaces, like Titan’s, have been resurfaced. However, mountains, as well as several potential cryolcanoes (ice volcanoes), have been observed on this strange and distant moon-world.