Jupiter is, to our eyes, a stunning symphony of folds—white clouds folding brown clouds, brown clouds folding blue clouds, light blue clouds folding dark blue clouds. What kind of beauty is this? And why is it able to stir the deepest parts of our souls?

Essentially, we are impressed by a world that is totally inhuman, unlivable, unthinkable. This confusion of clouds is alive in the deadest sense possible. It's matter behaving only as matter. Matter violently thrown this way and that by spin, wind, and pressure. Even our extremophiles (microbes that live in the most acidic, hottest, and coldest parts of Earth) would call Jupiter a living hell.

But it's precisely Jupiter's thoughtless hugeness that protects our thoughtful, music-making planet. Jupiter is big and dumb; Earth is small, delicate, and intelligent. The layer of life on our planet is not deep and is vulnerable. Sixty-five million years ago, an asteroid slammed into Earth and wiped out the dinosaurs. (This was lucky for us; mammals would still be small and hiding in the night if the dinosaurs were not exterminated by that asteroid.) But, as the UW professor Peter Ward points out in his book Rare Earth: Why Complex Life Is Uncommon in the Universe, hits by comets and asteroids would be more common if we did not have Jupiter protecting us. Jupiter's huge size and powerful gravity draw and deflect these life-threatening balls of ice. In 2009, a comet hit Jupiter with a force more powerful than a million Hiroshimas and left a scar the size of the Pacific Ocean. We got the brains; Jupiter got the brawn.