Venus & Moons, Page 10: [Previous Page] [Next Page] [Syllabus] Textbook pages 192 - 207

EXPLORING the outer MOONS: TITAN


We've looked closely at the terrestrial planets (the inner, rocky ones). The Gas Giants (Jupiter, Saturn, Uranus & Neptune) don't seem much like planets for life to form on. But how about their moons?

Titan is the fifteenth of Saturn's known satellites and the largest. Discovered in 1655 by Dutch physicist and astronomer, Christiaan Huygens. The orangy haze seen in the picture to the left is due to Titan's thick atmosphere, and we have no direct images of the surface.

Diameter = 5150 km (about 1/2 Earth)
Mass = 10²³ kg (about 1/50th Earth)
Density = 1.9 x Water (Earth is 5.5 x Water)
Sun Distance = 9 AU (9 x Earth-Sun distance)

Titan is in synchronous rotation with Saturn (tied to its 16 day orbital period around Saturn). It was thought Titan was the largest moon. But Titan's atmosphere is so thick, its now known that its solid surface is slightly smaller than Ganymede's (a moon of Jupiter's). However, Titan's radius is just less than Mercury's, but its larger and more massive than Pluto. It can, for all practical purposes, be considered a planet!



Titan's low density
Earth has a dense iron rich core, giving it its high density. Even the Moon has a significantly higher density, 3 x water, and is made mostly of silicate rock (little iron). Titan's low density suggests it contains a lot of frozen water, methane, carbon dioxide and ammonia.

Probably the dominant ice is water ice. Water ices are common and ubiquitous all over the outer solar system, in Jupiter, on the icy rings of Saturn and are the predominant ice found in Comets.

Titan's interior is primarily composed of ice existing in different phases. The drawing to the left shows a plausible description of the differing phases of ice in Titan's interior, becoming more densely packed as one moves towards the interior. At mid-depths in Titan, high pressures may allow for liquid water. Deep inside Titan are found the heavier, rocky and metal elements such as silicates and iron, which form the core of Titan.