Of all these pictures of our planetary neighbors, I think I might love this one the most. That's us: it's home. Blue, with feathered white, the only planet to really look this way (Uranus and Neptune are both blue, but for different reasons; we have water, they have methane). This picture is from Terra, a NASA Earth-observing satellite, designed to look down and investigate our environment.

But that's not why this picture really amazes me. Look at it more carefully: almost all you see is water! If you look to the upper right you'll see the west coast of the US, Baja California, and Mexico. Everything else you see is ocean. The satellite was over the Pacific when this was taken, and that expanse of water is vast, covering nearly an entire hemisphere of the planet. It's a coincidence that this is the way things are right now; continental drift changes the sizes of the oceans over geologic time scales. But still, it's a sharp reminder of just how much water we have here on Earth, and why we look for it so steadfastly on other worlds, and why we need to take our job as planetary caretakers more seriously.

Image credit: NASA

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