I've said this before, but it bears repeating: when I was a kid, Mars was a dead planet. Dry, frozen, with hardly any atmosphere, I always figured it wasn't very interesting. Heh. Mars may or may not be alive in the biological sense, but it's certainly active geologically! And images from the Mars Reconnaissance Orbiter's HiRISE camera verify it. It's spotted migrating ripples across Martian sand dunes:
These before and after images (part of a trio of them) show the motion. The image on the left was taken June 30, 2007, and the one on the right in October of that year. During that time, just a few months, the ripples can clearly be seen to have moved by a few meters (the inset diagram shows the ridges on the dunes schematically). This means that the wind blowing in this part of the planet is not only actively pushing around ...
