Not much is known of Titan¡¯s surface. Our knowledge of its surface comes from what we can see through long wavelength telescopes. Images from the Hubble Space Telescope (such as the lower-right picture above) revealed large-sized brightness variations. It is believed that this may be an area of different composition and/or roughness of material.
It is also speculated that Titan has a water-ice crust, much like other moons in the outer solar system. Temperatures in this part of the solar system are cold enough to make ice as hard as a rock. Weak spectral features have been found, indicating the presence of ice on Titan¡¯s surface. A dark substance was also detected, which may suggest something masking the water-ice.
Radars on Earth indicate a possibility of a surface similar to that of Callisto, one of Jupiter¡¯s moons. However, Titan¡¯s size alone points to a surface much like another one of Jupiter¡¯s moons, Ganymede. Ganymede¡¯s surface is modified by ice tectonics, but heavily cratered and old. Lakes of liquid hydrocarbons may be present on Titan, which could be formed by crater basins caused be Titan¡¯s possible tectonic activity.
Titan may have also incorporated as much as 15 percent ammonia. This may have occurred due to the fact that Titan was formed in a colder region of the solar system. Ammonia-water liquid may have been frozen under the water-ice surface and, since it is more buoyant, ammonia-water magma may have risen to the surface through cracks in the water-ice.
The Cassini-Huygens mission will hopefully provide us with more conclusive information on Titan's surface.
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