Changes on the surface of the Jovian moons, by contrast, look far
> older, perhaps 100 million years or more.
It's my understanding that new cracks open on Europa almost daily, and then the latest open crack extends continually for a major portion of one orbital period around Jupiter. Thus at any time we choose, there are changes on the surface of Europa less than a week old.
For more discussion on this topic, perhaps move to a more appropriate newsgroup? .