Fresh crater on Titan, image taken 29 Aug 2011 by Cassini

A radar image snapped last week by the Cassini probe of the surface of Titan revealed an unexpected result, shown above, in the form of a large crater. This one is about a dozen miles wide and appears to be quite fresh. It’s not surprising to see craters on moons in general, especially in the vicinity of Saturn. The planet’s exquisite rings attest to the violent nature of the system. But finding a large impact marker on Titan is unusual because of the unique properties of Saturn’s largest moon and that got me to think’n.

True-color image of layers of haze in Titan's atmosphere courtesy of NASA/JPL/ESA

Unlike every other moon we know of, Titan has a dense atmosphere, and unlike any planets we know of in the solar system, it has a defined terrestrial surface with material cycling through all three phases, solid, liquid, and gas in the way water does here at home (It happens to be methane and other hydrocarbons at a couple of hundred degrees below zero). The surface pressure is 50% higher than earth’s, far closer than any world we know of, so in all these respects Titan is the most earth-like object in the solar system. But the little moon’s gravity is only about one-seventh earth normal and the atmosphere extends outward much farther than our own. You know what that all means?

Only large objects make it to the surface, otherwise they burn up. But more importantly, Titan would be the most fun skydive in all the solar system! I am a skydiver, or at least I used to do it a lot, and the thought of that combo of thick atmosphere and low gravity would be a dream free-fall. A human body at Titan terminal velocity could almost land safely on the surface without a parachute, especially in one of its many lakes. I actually wrote up a sci-fi short story based around the idea but I could never get it to work. Maybe I’ll post parts of it here one day.