Looking at this story of Enceladus, the moon of Saturn of which I have never heard before, it struck me how different all the planets and particularly all the moons of the planets are – at least those big enough to have become spheres rather than large rocks.
The laws governing the planets are simple enough to produce orbits that have been relatively stable. There is the odd bit of chaos here and there – as in the case of Hyperion which tumbles through space in chaotic motion around Saturn. Yet except for quite small variations, the system has stayed the same for hundreds of millions of years.
So you’d think as we ventured up there we’d find some fairly strong patterns. There are a few obvious patterns. The inner planets are rocky, the outer ones are gaseous and have rings. And of course things get colder as you head away from the Sun (with a few exceptions like Venus which is hotter than mercury because it has the mother of all greenhouse effects).
But beyond these and perhaps a few other generalisations, the planets and particularly their moons just keep coming up with the most amazing surprises. They’re all so different.
I remember when I was quite young reading Fred Hoyle’s theory that there must be life elsewhere in the universe because the way we could tell a sensible story about how our solar system evolved suggested at least some other ones would be similar. And the sample size is pretty big! Well he may well be right, and its probably looking more like he’s right now than when he came up with the theory what with over a hundred planets discovered outside our solar system. Still I think he might be surprised at the variation within our own.
It certainly amazes me.