Sometimes, I see an image and do a double-take. This picture sure caused one:
[Click to barsoomenate.]
If I told you those were bacteria under a microscope, you might believe me for a minute or two. But actually, those are sand dunes on Mars!
Yup. It's funny how bizarre and alien Mars can be. What you're seeing in this image from the Mars Reconnaissance Orbiter HiRISE camera is actually two different kinds of sand: the dark stuff in the big dunes is actually made of grains of gray basaltic sand. They're heavy and pile up into dunes. The ripply pinkish stuff between the dunes is made of smaller grains of sand laden with iron oxide -- rust! The wind can shape those grains more easily, so they can form more gentle, smaller wavelike patterns. This is also why dust devils on Mars leave such amazing and intricate patterns.
Still, those dunes really look like microbes... and hey, wait a second. There are a set of characteristics that living things share: the ability to consume, excrete, multiply, and show complexity. Sand dunes consume, in a way: the wind brings in more sand to build them up. The excrete, too, by losing sand. They can grow, and split in half, making more. And in point of fact, they do show emergent complex behavior.
Maybe the dunes share more than just appearances with bacteria...could sand dunes actually be [dun dun dunnnnnn] alive*?
Image Credit: NASA/JPL-Caltech/University of Arizona