A Piece of Mars: Some things just go unexplained (so far, anyway). Here’s a mysterious bright streak (scene is 1.2×1.8 km, 0.75×1.12 mi) concentrated between two sets of ripple-like bedforms. It looks sort of like a river, but it’s on flat terrain and it’s not water. It’s part of a larger set of bright streaks that you can see throughout the top of this broader CTX image (the bright streak shown in detail here is visible as a distinct white stripe on the floor of a crater). My guess is that at some point, probably at least several million years ago, a bunch of fine bright silt was blown towards the north-northwest, settling in a few places. I’m guessing it’s silt (finer-grained than sand) because it didn’t form dunes, and it’s not as fine as the clay-sized dust that blows into dust storms because this stuff wasn’t completely blown away (dust is easily mobilized by saltating sand). (HiRISE ESP_052786_1740, NASA/JPL/Univ. of Arizona).