This morning, on my way into the office, I was thinking about Pluto and why its surface appears to be so young. I began to formulate a hypothesis in which Pluto, in the early days of the solar system, was actually in the inner solar system, then through gravitational interactions it was flung into the outer solar system before eventually being recaptured by Neptune’s gravity.

Then I did some reading on Wikipedia about theories on the formation of the solar system and planetary migration, in particular the Nice Model, and discovered that, no, my hypothesis while driving was probably not any sort of truth. The things I don’t know… and they’re fascinating!

It does appear, from the discovery of extrasolar planets, that our solar system is unique. We have inner rocky planets and gas giants further out, but many of the solar systems we’re finding in deep space have their gas giants much closer in, sometimes almost hugging their star. We’re unlikely to find rocky worlds, like Earth, in those solar systems’ habitable zones because the gas giants would have ejected (or consumed) such rocky worlds. Those solar systems, strange as they are, are almost certainly lifeless.

There’s some thought, which I read about recently, that it’s the interaction of Jupiter and Saturn that has made our solar system (generally) stable, that it’s Saturn’s gravitational influence that’s keeping Jupiter from wandering in, clearing out the inner solar system, and becoming one of those “Hot Jupiters.”

Now, it appears that we’ve found a solar system very similar to ours, with a Jupiter-scale gas giant at a good distance from its sun. Perhaps this newly discovered system has its own Saturn-like planet holding back its Jupiter.

If so, perhaps there are rocky worlds in closer orbit, perhaps even one or two in this system’s habitable zone.

We’re getting closer to discovering extrasolar planets that are in the right place, with the right size, for life. Perhaps, within fifty years, we’ll find one with life.

As Ellie’s father said in the movie version of Contact, “It’d be an awful waste of space” if we’re all alone in the Milky Way.

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