Some windblown dunes on Mars are just beyond words. Take these beasts in this 0.95×0.95 km (0.59×0.59 mi) scene:
These are a peculiar type of bedform called a transverse aeolian ridge, or TAR for short, with a spacing of about 50 m (164 ft). Nobody really understands these things: are they dunes or ripples or something totally different? They’re common on Mars but unusual (maybe even nonexistent) on Earth. They’re also pretty dark-toned here, whereas on most of Mars they tend to be lighter than the surrounding rocks.
The TARs mostly cover the surface, but you can see bright bits poking through in places. You can see layers sweeping around – this is a place where stuff (either sediment or volcanic rock) was deposited in successive layers. It may then have been tilted or deformed, and then it was eroded away to expose the bright layers. All that happened before the TARs piled up on top of them. Extra points if you can find a couple of old eroded crater floors – that tells us that the surface here was probably higher than it is now, and it was eroded down to the current level. So, you know, it’s yet another crazy landscape on Mars.