‘Young’ Moon 
Like an actress concealing her age with cosmetics and plastic surgery, the largest moon of Saturn is older than it looks. Like Saturn and the other planets and moons of the solar system, Titan is four-and-a-half billion years old. Yet its surface is only a few tens of millions of years old — rejuvenated by Titan’s own actions.
Scientists judge the age of the surface of a moon or planet by looking at impact craters. Every body in the solar system undergoes a constant pounding by space rocks large and small. The big rocks create large craters, like the ones that cover the face of our own moon.
The Moon itself keeps the impact craters because there’s nothing to erase them — no air, no rivers, and little or no volcanic activity. On active worlds like Earth, though, the craters are soon washed away or covered up.
And that’s what’s happening on Titan. It’s blanketed by a frigid atmosphere that’s thicker than Earth’s. Clouds of liquid methane and ethane in the atmosphere have produced rain that eroded some of the craters, and created rivers that erased more. Winds add to the constant process of resculpting the surface.
Some of the changes to Titan’s surface may come from below. Volcanoes may belch frozen or even liquid water onto the surface, where it paves over the existing terrain.
All of that activity has erased all but a few large craters from Titan’s surface — giving the ancient moon a youthful appearance.
More about Titan tomorrow.
Script by Damond Benningfield, Copyright 2012
This program was made possible in part by a grant from the NASA Science Mission Directorate.